Release laminated polyester film and release film

Abstract

To provide a laminated polyester film for release that is excellent in recyclability and surface smoothness.SOLUTION: A laminated polyester film for release comprises a polyester film one side of which comprises an easily soluble resin layer, the easily soluble resin layer comprising a polyester component, the polyester component comprising, as an acid component, (A) terephthalic acid, (B) dicarboxylic acid having a sulfonate group and (C) other dicarboxylic acid, and the easily soluble resin layer surface having an arithmetic average roughness Ra1 of 30 nm or less and a maximum projection height Rp1 of 150 nm or less.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a release laminated polyester film and a release film.

Background Art

[0002] Polyester films are excellent in mechanical properties, heat resistance, etc., and are also easily available in terms of price. Therefore, they are used in various applications as industrial materials. In particular, as process papers related to electronic components, it is used for release films for forming green sheets of multilayer ceramic capacitors, separators for liquid crystal polarizing plates, base materials for dry film resists, base materials for interlayer insulating resin release, etc.

[0003] In recent years, with the progress of the electrification of automobiles and the high functionality of smartphones, etc., and the increasing demand for electronic components, in particular, the miniaturization and high capacitance of multilayer ceramic capacitors (MLCC) have been progressing. When miniaturizing and increasing the capacitance of multilayer ceramic capacitors, the thinning of ceramic green sheets has been progressing. When it is made into a thin film, pinholes are generated in the ceramic green sheet or partial thickness variations occur due to minute protrusions on the surface of the process release film used in the manufacturing process of the multilayer ceramic capacitor. Therefore, surface smoothness is required for the release film.

[0004] Examples of smooth release polyester films include the following technologies. For example, in Patent Document 1, by setting the number of protrusions with a height of 1 μm or more and the center line average roughness of the surface within a specific range, a biaxially oriented polyester film for release having excellent surface smoothness and excellent surface characteristics in which the protrusions on the surface of the polyester film do not transfer to the sheet of the object to be released when a release layer is provided to form a release film is disclosed.

[0005] In Patent Document 2, a structure is disclosed in which there are a layer containing particles and a layer substantially free of particles, and the relationship between the average particle diameter in the former layer and the thickness of the latter layer is defined so that the surface of the release layer becomes smooth.

[0006] On the other hand, due to the increasing environmental problems in recent years, as PET bottle recycling is becoming widespread, recycling such as reuse and regeneration is also required in the field of polyester films. In particular, with the thinning of the green sheet, the number of green sheets to be laminated has increased, so the usage amount of the above-mentioned release film has increased, and the recycling of the release film has become an urgent issue.

[0007] As a recycling method, it is conceivable to recycle the release film by directly remelting it. However, especially in the application of laminated ceramic capacitors, problems such as clogging of the filter due to the remaining ceramic and inability to form a normal film occur. Moreover, even if the remaining ceramic is removed, since the material constituting the release layer is mixed into the molten polymer, it generates an abnormal odor during extrusion, or the melt viscosity of the polymer decreases, which causes breakage during film formation. Even if a film can be formed, deterioration in quality such as coloring of the obtained film is inevitable.

[0008] As a recycling method of the above-mentioned release film, for example, there is a technique disclosed in Patent Document 3. Patent Document 3 discloses a release film in which a release layer is formed via an easily soluble resin layer on at least one side of a base film. With such a configuration, after use, only the easily soluble resin layer can be dissolved, and by washing with a solvent that does not dissolve the base film, only the base film is separated and recovered from the release film.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

[0010] However, although the release polyester films of Patent Documents 1 and 2 have excellent surface smoothness, no consideration has been given to recyclability at all. On the other hand, although the release film described in Patent Document 3 is excellent in recyclability and there is a disclosure that it can be suitably used in the manufacturing process of multilayer ceramic capacitors, no consideration has been given to surface smoothness, and it may be difficult to use it without problems in practical use.

[0011] Therefore, the present invention has been made in view of the above circumstances, and the problem to be solved is to provide a release laminated polyester film excellent in recyclability and surface smoothness. MEANS FOR SOLVING THE PROBLEM

[0012] As a result of intensive studies, the present inventor has found that the above problems can be solved by using a release laminated polyester film having a specific configuration. The present invention has been completed based on such findings and has the following aspects.

[0013] [1] A release laminated polyester film having a readily soluble resin layer on one surface of a polyester film, wherein the readily soluble resin layer contains a polyester component, and the polyester component contains, as an acid component, (A) terephthalic acid, (B) a dicarboxylic acid having a sulfonate group, and (C) other dicarboxylic acids, and the arithmetic mean roughness Ra1 of the surface of the readily soluble resin layer is 30 nm or less and the maximum protrusion height Rp1 is 150 nm or less.

[0014] [2] The release laminated polyester film according to [1] above, wherein the component (B) contains at least sodium 5-sulfoisophthalate.

[0015] [3] The release laminated polyester film according to [1] or [2] above, wherein the component (C) contains at least isophthalic acid.

[0016] [4] The release laminated polyester film according to any one of [1] to [3] above, wherein the maximum protrusion height Rp1 on the surface of the easily soluble resin layer is 10 nm or more.

[0017] [5] The release laminated polyester film according to any one of [1] to [4] above, wherein the ratio (Rp1 / t) of the maximum protrusion height Rp1 (nm) on the surface of the easily soluble resin layer to the thickness t (nm) of the easily soluble resin layer is 0.01 to 0.25.

[0018] [6] The release laminated polyester film according to any one of [1] to [5] above, which is used in the manufacturing process of a multilayer ceramic capacitor.

[0019] [7] A release film having a release layer on the easily soluble resin layer of the release laminated polyester film according to any one of [1] to [6] above.

[0020] [8] The release film according to [7] above, wherein the arithmetic mean roughness Ra2 on the surface of the release layer is 30 nm or less.

[0021] [9] The release film according to [7] or [8] above, wherein the maximum protrusion height Rp2 on the surface of the release layer is 125 nm or less.

[0022]

[10] The release film according to any one of [7] to [9] above, which is used in the manufacturing process of a multilayer ceramic capacitor.

[0023]

[11] A mold release layer removing method including a mold release layer removing step of cleaning the mold release film according to any one of [7] to

[10] above with a cleaning agent to remove the mold release layer from the polyester film together with the easily soluble resin layer.

[0024]

[12] The mold release layer removing method according to

[11] above, wherein the cleaning agent is water.

Advantages of the Invention

[0025] The laminated polyester film for mold release of the present invention is excellent in recyclability and surface smoothness, and can be suitably used as a mold release film for use in the manufacturing process of laminated ceramic capacitors.

Brief Description of the Drawings

[0026]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0027] Next, an example of an embodiment of the present invention will be described. However, the present invention is not limited to the embodiments described below.

[0028] <<Laminated Polyester Film for Mold Release>> The laminated polyester film for mold release in the present invention (hereinafter also referred to as "this film") has an easily soluble resin layer on one surface of a polyester film that is a base film, the easily soluble resin layer contains a polyester component, the polyester component contains, as an acid component, (A) terephthalic acid, (B) a dicarboxylic acid having a sulfonate group, and (C) other dicarboxylic acids, and the arithmetic mean roughness Ra1 of the surface of the easily soluble resin layer is 30 nm or less, and the maximum protrusion height Rp1 is 150 nm or less.

[0029] <Polyester Film> The polyester film (base film) constituting this film may have a single-layer structure or a multilayer structure. In the case of a multilayer structure, it may have a two-layer structure, a three-layer structure, etc., and may have four or more layers as long as it does not deviate from the gist of the present invention, and the number of layers is not particularly limited. Also, the polyester film may be an unstretched film (sheet) or a stretched film. Among them, it is preferably a stretched film stretched in a uniaxial direction or a biaxial direction, and more preferably a biaxially stretched film from the viewpoints of the balance of mechanical properties, flatness, and thinning of the film.

[0030] The polyester constituting the polyester film is not particularly limited, and those commercially available can be appropriately used. Specifically, polyesters formed by polycondensing dicarboxylic acids and diols can be mentioned. As the dicarboxylic acid, aromatic dicarboxylic acids are preferred, and as the diol, aliphatic glycols are preferred. The polyester film preferably contains polyester as the main component. Also, in the case where the polyester film has a multilayer structure, it is preferable that the main component resin of each layer is polyester. Note that the "main component resin" means the resin having the highest content ratio among the resins constituting each layer. For example, it is a resin that occupies 50% by mass or more, particularly 70% by mass or more, and especially 80% by mass or more (including 100% by mass) among the resins constituting each layer.

[0031] Examples of the above aromatic dicarboxylic acids include terephthalic acid, 2,6-naphthalenedicarboxylic acid, isophthalic acid, phthalic acid, etc. Examples of the above aliphatic glycols include ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, 1,4-cyclohexanedimethanol, neopentyl glycol, etc.

[0032] The polyester may be a homopolyester or a copolyester. Specific examples of the polyester include polyethylene terephthalate, polyethylene-2,6-naphthalate, polybutylene terephthalate, polybutylene-2,6-naphthalate, etc., and among these, polyethylene terephthalate is preferred.

[0033] Further, the polyester may be a copolyester containing, as a copolymerization component, a third component other than the dicarboxylic acid constituting the polyester, preferably the compound that is the main component of the aromatic dicarboxylic acid, and the diol, preferably the compound that is the main component of the aliphatic glycol. For example, in polyethylene terephthalate, the third component is a component other than terephthalic acid and ethylene glycol. Specifically, polyethylene terephthalate may have dicarboxylic acid units other than terephthalic acid units in an amount of about 30 mol% or less out of 100 mol% of the dicarboxylic acid units, and may also have diol units other than ethylene glycol units in an amount of about 30 mol% or less out of 100 mol% of the diol units.

[0034] There is no particular limitation on the polymerization catalyst for the polyester, and conventionally known compounds can be used. For example, titanium compounds, germanium compounds, antimony compounds, manganese compounds, aluminum compounds, magnesium compounds, calcium compounds, etc. can be mentioned.

[0035] In order to suppress the precipitation amount of the oligomer component, a polyester film may be produced using a polyester with a low content of the oligomer component as a raw material. As a method for producing a polyester with a low content of the oligomer component, various known methods can be used, such as a method of performing solid-phase polymerization after polyester production. Further, the polyester film may have a three-layer or more structure, and by making the outermost layer of the polyester film a layer using a polyester raw material with a low content of the oligomer component, the precipitation amount of the oligomer component may be suppressed. The polyester may be obtained by performing an esterification or transesterification reaction and then further increasing the reaction temperature and performing melt polycondensation under reduced pressure.

[0036] It is also possible to incorporate particles into the polyester film for the main purpose of imparting easy slippage and preventing scratches in each process. The type of particles is not particularly limited as long as it is a particle capable of imparting easy slippage, and specific examples include inorganic particles such as silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, magnesium phosphate, kaolin, aluminum oxide, and titanium oxide, as well as crosslinked polymer particles such as crosslinked silicone resin particles, crosslinked acrylic resin particles, crosslinked styrene-acrylic resin particles, and crosslinked polyester particles, and organic particles such as calcium oxalate and ion exchange resin. Examples of the composition of the crosslinked polymer particles include crosslinked polymer particles such as divinylbenzene polymer, ethylvinylbenzene-divinylbenzene copolymer, styrene-divinylbenzene copolymer, styrene-ethylvinylbenzene-divinylbenzene copolymer, ethylstyrene-methyl methacrylate-divinylbenzene copolymer, ethylene glycol dimethacrylate polymer, styrene-ethylene glycol dimethacrylate copolymer, and methyl methacrylate-divinylbenzene copolymer. The crosslinked polymer particles may be composed of a system of three or more components. The particles may be used alone or in combination of two or more kinds. Furthermore, precipitated particles obtained by precipitating and finely dispersing a part of a metal compound such as a catalyst during the polyester production process can also be used as the above particles.

[0037] The shape of the particles to be used is not particularly limited, and any of spherical, block, rod-like, flat, etc. may be used. There is also no particular restriction on the hardness, specific gravity, color, etc. These particles may be used alone or in combination of two or more kinds, if necessary.

[0038] The average particle size of the particles used is generally in the range of 0.01 to 5 μm, preferably 0.03 to 4 μm, and more preferably 0.05 to 3 μm, in consideration of both the transparency and ease of handling of the film.

[0039] When the polyester film has a multilayer structure and contains particles, the particles may be contained in at least one of the plurality of layers. When the polyester film has a surface layer and an intermediate layer, the particles are preferably contained in the surface layer. The particles may be contained in one surface layer or both surface layers. By containing the particles in the surface layer, it is possible to effectively impart slidability and the like while reducing the content of the particles in the entire polyester film.

[0040] The content of the particles in the layer containing the particles is usually in the range of 0.01% by mass or more and less than 10% by mass, preferably 0.01 to 5% by mass, and more preferably 0.01 to 3% by mass. When there are no particles or the amount is small, the transparency of the polyester film is increased, and it becomes a polyester film with good transparency from the viewpoint of transparency. On the other hand, by containing the particles within the above range, it also becomes good in terms of slipperiness. In addition, when the layer containing the particles has a multilayer structure, it is preferably the surface layer, but when the polyester film has a single-layer structure, it is the entire polyester film.

[0041] The method of adding particles to the polyester film is not particularly limited, and a conventionally known method can be adopted. For example, it can be added at any stage of producing the resin (for example, polyester) constituting each layer, but in the case of polyester, it is preferably added after the esterification or transesterification reaction is completed.

[0042] In addition, in the polyester film, additives such as conventionally known antioxidants, antistatic agents, ultraviolet absorbers, heat stabilizers, lubricants, dyes, and pigments can be added as necessary in addition to the above-mentioned particles. When the polyester film has a multilayer structure, each additive may be added to at least one of the plurality of layers.

[0043] The arithmetic mean roughness Ra of the surface on the side of the easily soluble resin layer of the polyester film 01is preferably 50 nm or less, more preferably 45 nm or less, still more preferably 40 nm or less, particularly preferably 35 nm or less, and especially preferably 30 nm or less. On the other hand, the lower limit is preferably 5 nm or more, more preferably 7 nm or more, and still more preferably 10 nm or more. Also, the maximum surface protrusion height Rp on the side of the easily soluble resin layer of the polyester film 01 is preferably 500 nm or less, more preferably 300 nm or less, still more preferably 200 nm or less, particularly preferably 150 nm or less. On the other hand, the lower limit is preferably 10 nm or more, more preferably 20 nm or more, still more preferably 30 nm or more, particularly preferably 50 nm or more, and especially preferably 90 nm or more. The Ra on the side of the easily soluble resin layer of the polyester film 01 and Rp 01 If they are below the upper limit value, the unevenness on the side of the easily soluble resin layer of the polyester film can be more suitably filled by the easily soluble resin layer described later, and the surface of the easily soluble resin layer can be smoothed. As a result, when a release layer is formed on the easily soluble resin layer, it is possible to preferably prevent the unevenness of the polyester film from affecting the surface of the release layer. On the other hand, the Ra on the side of the easily soluble resin layer of the polyester film 01 and Rp 01 , especially Rp 01 If it is above the lower limit value, the polyester film will have appropriate protrusions, and the adhesion to the easily soluble resin layer will be improved due to the physical anchor effect, which is preferable.

[0044] The arithmetic mean surface roughness Ra on the side of the polyester film opposite to the easily soluble resin layer 02 is preferably 50 nm or less, more preferably 45 nm or less, still more preferably 40 nm or less, particularly preferably 35 nm or less, and especially preferably 30 nm or less. On the other hand, the lower limit is preferably 5 nm or more, more preferably 7 nm or more, and still more preferably 10 nm or more. Also, the maximum surface protrusion height Rp on the side of the easily soluble resin layer of the polyester film 02 is preferably 500 nm or less, more preferably 300 nm or less, still more preferably 200 nm or less, and particularly preferably 150 nm or less. On the other hand, the lower limit is preferably 10 nm or more, more preferably 20 nm or more, still more preferably 30 nm or more, particularly preferably 50 nm or more, and especially preferably 90 nm or more. The Ra 02 and Rp 02 on the side opposite to the easily soluble resin layer of the polyester film, if they are above the lower limit value, the handleability and wrinkle suppression during winding the release film in a roll shape and after winding and storing are improved. On the other hand, the Ra 02 and Rp 02 on the side opposite to the easily soluble resin layer of the polyester film, if they are below the upper limit value, it is possible to prevent the transfer to the ceramic layer due to protrusions and the destruction of the ceramic layer when in a roll shape.

[0045] The thickness of the polyester film is not particularly limited as long as it can be formed into a film, but is preferably in the range of 9 to 50 μm, more preferably in the range of 19 to 38 μm, and still more preferably in the range of 25 to 32 μm. Within such a range, while making the strength of the film appropriate, when used as a release film, the amount of the recycled release film can be suppressed.

[0046] Next, the production examples of the polyester film will be specifically described, but it is not limited to the following production examples. For example, when producing a biaxially stretched film, a method of extruding the polyester used as the raw material described above from a die as a molten sheet using an extruder and cooling and solidifying it with a cooling roll to obtain an unstretched sheet is preferable. In this case, in order to improve the flatness of the sheet, it is preferable to enhance the adhesion between the sheet and the rotating cooling drum, and the electrostatic printing adhesion method and / or the liquid coating adhesion method are preferably adopted. In this way, an unstretched sheet is obtained. Incidentally, the polyester used as the raw material may be appropriately dried as pellets or the like and then supplied to an extruder. Further, particles, an ultraviolet absorber, and other additives may be appropriately blended into the pellets.

[0047] Next, the obtained unstretched sheet is stretched in a biaxial direction. In that case, first, the unstretched sheet is stretched in one direction by a roll or tenter-type stretching machine. The stretching temperature is usually 70 to 120°C, preferably 80 to 110°C, and the stretching ratio is usually 2.5 to 7 times, preferably 3 to 6 times. Subsequently, it is stretched in a direction perpendicular to the stretching direction of the first stage. In that case, the stretching temperature is usually 70 to 170°C, and the stretching ratio is usually 3 to 7 times, preferably 3.5 to 6 times.

[0048] Subsequently, heat treatment is carried out at a temperature of 180 to 270°C under tension or with relaxation within 30% to obtain a biaxially stretched film. In the above stretching, a method of performing the stretching in one direction in two or more stages can also be adopted. In that case, it is preferable to perform the stretching so that the final biaxial stretching ratios are within the above ranges respectively.

[0049] In addition, a simultaneous biaxial stretching method can also be adopted for the production of the polyester film. The simultaneous biaxial stretching method is a method of simultaneously stretching and orienting the above-mentioned unstretched sheet in the longitudinal direction and the width direction in a state where the temperature is controlled to usually 70 to 120°C, preferably 80 to 110°C. The stretching ratio is 4 to 50 times, preferably 7 to 35 times, and more preferably 10 to 25 times in terms of area ratio. Subsequently, heat treatment is carried out at a temperature of 170 to 250°C under tension or with relaxation within 30% to obtain a stretched and oriented film. Regarding the simultaneous biaxial stretching device adopting the above-mentioned stretching method, conventionally known stretching methods such as a screw method, a pantograph method, and a linear drive method can be adopted.

[0050] Note that the longitudinal direction of the film refers to the direction in which the film advances in the film manufacturing process, that is, the winding direction of the film roll. The width direction refers to the direction parallel to the film surface and orthogonal to the longitudinal direction, that is, the direction parallel to the central axis of the roll when the film is in the form of a film roll.

[0051] <Easily soluble resin layer> This film has an easily soluble resin layer (hereinafter also referred to as "this easily soluble resin layer") on one surface of the polyester film. This easily soluble resin layer has a function of reducing the influence of the unevenness of the polyester film on the surface of the release layer preferably provided on the easily soluble resin layer. That is, this easily soluble resin layer can preferably fill the unevenness on the easily soluble resin layer side of the polyester film, and as a result, the surface of the easily soluble resin layer can be smoothed. By providing this easily soluble resin layer in this way, even if the unevenness on the easily soluble resin layer side of the polyester film is relatively large, the influence of the unevenness of the polyester film on the surface of the release layer can be reduced, and a laminated polyester film for release and a release film excellent in smoothness can be obtained.

[0052] In addition, by providing this easily soluble resin layer between the polyester film and the release layer described later, when the used release film is washed with a specific cleaning agent, the easily soluble resin layer is dissolved in the cleaning agent, and at the same time, the release layer and the residue and impurities (especially ceramics) attached to the release layer can be completely separated and removed. That is, since the polyester film, which is the base film, can be separated and recovered from the release film, it has excellent recyclability.

[0053] This easily soluble resin layer contains a polyester component, and the polyester component contains, as a dicarboxylic acid component, that is, an acid component, (A) terephthalic acid (hereinafter also referred to as "(A) component"), (B) a dicarboxylic acid having a sulfonate group (hereinafter also referred to as "(B) component"), and (C) other dicarboxylic acids (hereinafter also referred to as "(C) component"). The "polyester component" refers to the constituent components of a polyester obtained by polycondensation of at least one dicarboxylic acid component and at least one diol component.

[0054] The components (A) to (C) in the polyester component may be derived from a single polyester constituting the readily soluble resin layer, or may be derived from different polyesters. The readily soluble resin layer may be formed of, for example, a copolyester containing the components (A), (B), and (C). Also, for example, among the components (A), (B), and (C), a copolyester containing at least two components, specifically, a copolyester containing the components (A) and (B), a copolyester containing the components (A) and (C), or a copolyester containing the components (B) and (C) may be used to form the readily soluble resin layer.

[0055] Furthermore, the readily soluble resin layer may be formed by combining a plurality of polyesters composed of a single dicarboxylic acid component such as a homopolyester so as to contain the components (A) to (C). In addition to the copolyester, a polyester composed of a single dicarboxylic acid component such as a homopolyester may be used in combination. Thus, in any case, it is sufficient that the components (A) to (C) are contained in the readily soluble resin layer as a result. Also, the components (A) to (C) may all be derived from different polyesters (regardless of whether they are homopolyesters or copolyesters).

[0056] As described above, the readily soluble resin layer contains a polyester component, and the polyester component contains the components (A), (B), and (C) as acid components, but these do not necessarily have to be contained as a copolyester, and may be a blend of polyesters containing each component. It is preferable that the component (B) is contained as one of the acid components of the copolyester. In addition, for polyesters composed of one type of dicarboxylic acid component such as homopolyesters, it is preferable that the dicarboxylic acid component is terephthalic acid, and it is preferable that the homopolyester is polyethylene terephthalate (PET).

[0057] This easily soluble resin layer contains a polyester component, and by containing the (B) dicarboxylic acid having a sulfonate group as an acid component in the polyester component, that is, the (B) component, the water solubility of the easily soluble resin layer becomes easy. Examples of the (B) component include alkali metal salts, alkaline earth metal salts, ammonium salts, etc. such as sulfoterephthalic acid, 5-sulfoisophthalic acid, 4-sulfoisophthalic acid, 4-sulfonaphthalene-2,7-dicarboxylic acid. Among them, from the viewpoint of solubility in detergents, it is preferable to contain at least sodium 5-sulfoisophthalate. These (B) components may be used alone or in combination of two or more. In the present invention, the (A) component is terephthalic acid excluding the (B) component among the acid components contained in the polyester component.

[0058] The (C) other dicarboxylic acids, that is, the (C) component may be any dicarboxylic acid other than the (A) component and the (B) component, and examples include isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, and sebacic acid. By containing the (C) component, the solubility in water is improved. The principle of improving the solubility in water is presumed to be that by containing the (C) component, the glass transition temperature of this easily soluble resin layer becomes appropriate, and the resistance to heat and water becomes appropriate. As a result, it is considered that the solubility of this easily soluble resin layer in water is improved. More specifically, the glass transition temperature is preferably 50 °C or higher, more preferably 55 °C or higher, and still more preferably 60 °C or higher. Regarding the upper limit value, 85 °C or lower is preferable, more preferably 80 °C or lower, and still more preferably 75 °C or lower. These (C) components may be used individually or in combination of two or more types. However, at least one type is preferably isophthalic acid. By including isophthalic acid as the (C) component, the compatibility with (A) terephthalic acid and sodium 5-sulfoisophthalate suitable as the (B) component is good.

[0059] In this easily soluble resin layer, the content ratio of the (A) component in all acid components is preferably 50 to 85 mol%, more preferably 55 to 80 mol%, and even more preferably 60 to 75 mol%. When it is above the above lower limit value, an appropriate amount of the (C) component can be ensured while ensuring the moldability and strength of the film. When it is below the above upper limit value, the content of the (B) component can be ensured. Therefore, the solubility of the easily soluble resin layer in water becomes sufficient. Note that the "total acid component" means all polyesters constituting this easily soluble resin layer, that is, the dicarboxylic acid component in the polyester component.

[0060] In this easily soluble resin layer, the content ratio of the (B) component in all acid components is preferably 8 mol% or less, more preferably 7 mol% or less, and even more preferably 6 mol% or less. Also, the lower limit value is not particularly limited as long as it exceeds 0%, but it is preferably 1 mol% or more, more preferably 2 mol% or more, and even more preferably 3 mol% or more. Within such a range, the water-solubility becomes good.

[0061] In this easily soluble resin layer, the content ratio of the (C) component in all acid components is preferably 14 to 42 mol%, more preferably 18 to 38 mol%, and even more preferably 20 to 35 mol%. When it is above the above lower limit value, it is advantageous in terms of solubility in water. When it is below the above upper limit value, the content of the (B) component can be ensured. Therefore, the solubility of the easily soluble resin layer in water becomes sufficient.

[0062] The diol component in the polyester component is not particularly limited, and examples thereof include ethylene glycol, diethylene glycol, propylene glycol, butanediol, 1,4-cyclohexanedimethanol, and neopentyl glycol. The above diol component may be used alone or in combination of two or more. Here, it is preferable that at least one kind is ethylene glycol. By containing ethylene glycol as the diol component in this easily soluble resin layer, crystallinity is maintained, and the heat resistance and strength, which are the basic properties of the film, are improved. The content of ethylene glycol is preferably in the range of 40 to 100 mol%, more preferably in the range of 60 to 100 mol%, still more preferably in the range of 80 to 100 mol%, and particularly preferably in the range of 80 to 96 mol% in all the diol components.

[0063] In general, when polyester is produced (polycondensed) using ethylene glycol as one of the raw materials, diethylene glycol is by-produced from ethylene glycol. In this specification, this diethylene glycol is referred to as by-produced diethylene glycol. The amount of by-produced diethylene glycol from ethylene glycol varies depending on the mode of polycondensation and the like, but is about 5 mol% or less of ethylene glycol. In the present invention, the by-produced diethylene glycol of 5 mol% or less is also included in ethylene glycol. On the other hand, depending on the content of diethylene glycol, more specifically, when diethylene glycol is contained in an amount exceeding 5 mol%, diethylene glycol is distinguished from ethylene glycol.

[0064] This easily soluble resin layer may contain the above-described polyester component, and may also contain other resin components other than the polyester component.

[0065] Also, the easily soluble resin layer may contain particles from the viewpoints of imparting easy slipperiness and preventing the occurrence of scratches in each process. As the particles, the same particles as those contained in the polyester film can be used, and the particle size, content, etc. are also the same.

[0066] The arithmetic mean roughness Ra1 on the release layer side of the easily soluble resin layer surface, that is, the easily soluble resin layer when further including a release layer as described later, is 30 nm or less. When the above Ra1 exceeds 30 nm, the unevenness of the polyester film affects the surface of the release layer, and the smoothness of the release layer surface is inferior. The arithmetic mean roughness Ra1 on the release layer side of the easily soluble resin layer is preferably 27 nm or less, more preferably 24 nm or less, still more preferably 22 nm or less, particularly preferably 15 nm or less, and most preferably 10 nm or less. On the other hand, the lower limit value is preferably 1 nm or more, more preferably 2 nm or more, and still more preferably 3 nm or more.

[0067] Also, the maximum protrusion height Rp1 on the release layer side of the easily soluble resin layer surface, that is, the easily soluble resin layer when further including a release layer as described later, is 150 nm or less. When the above Rp1 exceeds 150 nm, the unevenness of the polyester film affects the surface of the release layer, and the smoothness of the release layer surface is inferior. The maximum protrusion height Rp1 on the release layer side of the easily soluble resin layer is preferably 130 nm or less, more preferably 120 nm or less, still more preferably 100 nm or less, particularly preferably 80 nm or less, and most preferably 50 nm or less. On the other hand, the lower limit value is preferably 10 nm or more, more preferably 15 nm or more, and still more preferably 20 nm or more.

[0068] If Ra1 and Rp1 on the surface of the easily soluble resin layer are below the upper limit values, as shown in FIG. 1, it is possible to more preferably prevent the unevenness of the polyester film from affecting the surface of the release layer, and the surface of the release layer can be made smooth. On the one hand, if Ra1 and Rp1, especially Rp1, on the surface of the easily soluble resin layer are at or above the lower limit values, the surface of the easily soluble resin layer will have appropriate protrusions, and the adhesion to the release layer will be improved by the physical anchor effect.

[0069] The thickness t (nm) of the easily soluble resin layer in this film is preferably 100 to 5000 nm, more preferably 300 to 3000 nm, and even more preferably 400 to 2000 nm. Within such a range, by more accurately filling the unevenness on the surface of the polyester film, the smoothness of the surface of this film can be made good, and at the same time, it can have excellent recyclability.

[0070] Also, the ratio (Rp1 / t) of the maximum protrusion height Rp1 (nm) on the surface of the easily soluble resin layer to the thickness t (nm) of the easily soluble resin layer is preferably 0.01 to 0.25, more preferably 0.01 to 0.20. If the ratio is at or above the lower limit value, appropriate protrusions on the surface of the easily soluble resin layer will cause a physical anchor effect, improving the adhesion to the release layer. Also, the thickness of the easily soluble resin layer will be appropriate, and it will have excellent recyclability. On the other hand, if the ratio is at or below the upper limit value, the smoothness of the surface of the easily soluble resin layer will be good. Also, the thickness of the easily soluble resin layer is ensured, and it has sufficient recyclability.

[0071] The manufacturing method of the easily soluble resin layer is not particularly limited, and it may be provided by in-line coating that treats the film surface during the film-forming process of the polyester film, or it may be provided by off-line coating that is applied outside the system on the once-manufactured polyester film. This film can be manufactured, for example, by applying an aqueous solution of 5 to 20% by mass of the resin constituting the easily soluble resin layer on a polyester film in an amount to achieve a desired dry coating thickness, heating at 80 to 150 °C for 1 to 10 minutes, and then heating at 100 to 200 °C for 1 to 30 seconds.

[0072] <<Release Film>> The release film in the present invention (hereinafter also referred to as "the present release film") has a release layer on the easily soluble resin layer of the release laminate polyester film. By laminating the release layer on the easily soluble resin layer side of the present release film, due to the excellent smoothness on the easily soluble resin layer side, when forming a green sheet by laminating a ceramic layer, particularly an ultra-thin layer ceramic layer, on the release layer, the occurrence of pinholes and the like is less likely to occur.

[0073] In addition, the release layer not only has the function of imparting releasability, but also has the function of more accurately embedding the unevenness remaining on the easily soluble resin layer as shown in FIG. 2. That is, the release layer of the present release film also contributes to further high smoothness.

[0074] <Release layer> The release layer is formed from a release agent composition containing a release agent. From the viewpoint of obtaining good release performance, it is particularly preferable to contain a silicone resin in the release agent composition. Specifically, it is preferable to contain a type mainly composed of a curable silicone resin, a modified silicone type by graft polymerization with an organic resin such as a urethane resin, an epoxy resin, an alkyd resin, or a fluorosilicone resin.

[0075] As the curable silicone resin, any existing curing reaction type such as an addition type, a condensation type, etc., which are thermosetting types, or an electron beam curing type such as an ultraviolet curing type can be used, and a plurality of types of curable silicone resins can also be used in combination. In addition, the coating form of the curable silicone resin when forming the release layer is not particularly limited, and it may be in a form dissolved in an organic solvent, in the form of an aqueous emulsion, or in a solvent-free form.

[0076] In addition to the above, the release agent composition for forming the release layer may also contain a binder, an antifoaming agent, a coating property improver, a thickener, inorganic and organic particles, an organic lubricant, an antistatic agent, a conductive agent, an ultraviolet absorber, an antioxidant, a foaming agent, dyes and pigments, etc. as required.

[0077] The release layer is provided by coating a release agent composition on the easily soluble resin layer of the present film. Examples of the method for providing the release layer include conventionally known coating methods such as reverse gravure coating, direct gravure coating, roll coating, die coating, bar coating, curtain coating, etc.

[0078] Regarding the curing conditions when forming the release layer, there is no particular limitation. Usually, heat treatment is preferably carried out with a temperature of 80°C or higher for 3 seconds or more, preferably 100 - 200°C for 3 - 40 seconds, more preferably 120 - 180°C for 3 - 40 seconds as a guide.

[0079] Also, if necessary, heat treatment and irradiation with active energy rays such as ultraviolet irradiation may be used in combination. As the energy source for curing by irradiation with active energy rays, known devices and energy sources can be used.

[0080] The coating amount (after drying) of the release layer is usually 0.005 - 5 g / m 2 , preferably 0.01 - 1 g / m 2 , more preferably 0.03 - 0.5 g / m 2 , still more preferably 0.05 - 0.1 g / m 2 in the range. If the coating amount (after drying) is 0.005 g / m 2 or more, the coatability becomes good and a uniform coating film can be obtained. On the other hand, if it is 5 g / m 2 or less, the coating film adhesion, curability, etc. of the release layer itself become sufficient.

[0081] The surface arithmetic mean roughness Ra2 on the release layer side of the present release film is preferably 30 nm or less, more preferably 25 nm or less, still more preferably 20 nm or less, particularly preferably 15 nm or less, and especially preferably 10 nm or less. On the other hand, the lower limit value may be 0 nm or more and is not particularly limited. Further, the maximum surface protrusion height Rp2 on the release layer side of the present release film is preferably 125 nm or less, more preferably 120 nm or less, still more preferably 80 nm or less, particularly preferably 70 nm or less, and most preferably 50 nm or less. On the other hand, the lower limit value may be 0 nm or more and is not particularly limited. If Ra2 and Rp2 on the release layer side of the present release film are below the upper limit values, it is possible to prevent the occurrence of pinholes in the ceramic green sheet or partial thickness variations due to minute protrusions on the surface of the release layer.

[0082] Since the present release film has a structure in which a readily soluble resin layer is interposed between a polyester film as a base film and a release layer, by washing with a cleaning agent described later, the readily soluble resin can be dissolved in the cleaning agent, and at the same time, the release layer can be completely removed together with the readily soluble resin layer, and only the polyester film can be recovered.

[0083] [[Release Layer Removal Method]] As described above, since the present release film has a readily soluble resin layer, it is easy to remove the release layer formed on the readily soluble resin layer. As the method for removing the release layer (hereinafter, also referred to as "the present release layer removal method"), there is a method including a release layer removal step of washing the present release film with a cleaning agent described later to dissolve the readily soluble resin layer and remove the release layer together with the readily soluble resin layer from the polyester film.

[0084] [[Cleaning Agent]] The cleaning agent is not particularly limited as long as it can dissolve only the readily soluble resin layer without dissolving the polyester film, but from the viewpoint of environmental load, it is preferable to use water. In addition, in order to improve the wettability with the polyester film, a surfactant or the like may be added to the water.

[0085] [[Release Layer Removal Step]] As a method for cleaning the present release film in the above-described release layer removal step, for example, there may be mentioned an immersion method of immersing in a cleaning tank containing a cleaning agent, a coating method of applying a cleaning agent in a solution state, a spraying method of spraying a cleaning agent in a solution state or a vaporized cleaning agent, and the like. Among these, from the viewpoint of the penetrability of the cleaning agent, the immersion method is preferred.

[0086] As the temperature of the cleaning agent in the immersion method, it is preferably room temperature (20°C) or higher. From the viewpoint of improving solubility, it is more preferably 40°C or higher, still more preferably 50°C or higher, and particularly preferably 60°C or higher. Further, as the upper limit value of the temperature of the cleaning agent, when the cleaning agent is used in a solution state, a temperature below the boiling point is preferred. From the above viewpoints, 100°C or lower is preferred, and 90°C or lower is more preferred. In addition, even in cases other than the immersion method, the temperature of the cleaning agent during cleaning is the same as above.

[0087] Regarding the immersion time, it is preferably 1 second or more and 30 minutes or less. When the immersion time is 1 second or more, the cleaning agent can sufficiently penetrate into the easily soluble resin layer and the cleaning performance can be exhibited. On the other hand, when it is within 30 minutes, the polyester film will not dissolve excessively. From the above viewpoints, it is more preferably 15 seconds or more and 30 minutes or less, still more preferably 30 seconds or more and 25 minutes or less, and particularly preferably 1 minute or more and 20 minutes or less.

[0088] The specific mode of the release layer removal step in the present release layer removal method is specifically as follows according to the shape of the release film which is waste material.

[0089] When the release film which is waste material is in a roll shape, it is preferable to install an unwinding device in front of the cleaning tank containing the cleaning agent, unwind the release film from the device, introduce it into the cleaning tank and clean it. And a mode of continuously shifting to the next recovery step is preferred. In addition, in the release layer removal step, for the purpose of efficiently removing the release layer from the release film, equipment equipped with physical means such as a roll brush, ultrasonic waves, micro / nano bubbles, water flow, or compressed cold air may be provided.

[0090] When the release film, which is a waste material, is in a lump form, it is preferable to install a cutting device before the release layer removal step, cut it into flakes, and introduce it into a cleaning tank containing the above-mentioned cleaning agent. By cutting it into flakes, the contact area between the release film and the cleaning agent becomes large, making it easier for the cleaning agent to penetrate into the easily soluble resin layer, and the release layer can be efficiently removed. In this embodiment, a method of continuously introducing the flake-shaped release film into the cleaning tank using a belt conveyor or the like is preferable. By adopting such an embodiment, cleaning can be performed with high productivity. In this embodiment, cleaning can also be performed in a batch manner.

[0091] <Recovery process> In the present release layer removing method, a recovery step of recovering the polyester film may be included after the release layer removing step. Also, a rinsing step and a drying step may be included before the recovery step. As the recovery method, an appropriate method can be selected depending on the shape of the release film, which is a waste material. When the release film as waste material is in the form of a roll, it can be efficiently recovered by continuously carrying out the processes of roll-to-roll, appropriately going through the release layer removing step, rinsing step, and drying step, and then winding it up. Furthermore, in the case where the release film as waste material is in a lump form, as described above, a cutting step is provided before the release layer removal step, and the cut release film in flake form is continuously passed through a release layer removal step, a rinsing step, and a drying step using a belt conveyor or the like to recover the polyester flakes. The polyester recovered as described above is advantageously pelletized in terms of handling after recovery.

[0092] <Rinse process> In this release layer removal method, a rinsing step of flushing away the cleaning agent may be provided between the release layer removal step and the recovery step. This is a step of flushing away the cleaning agent adhering to the polyester film from which the easily soluble resin layer and the release layer have been removed with the rinsing liquid. Water is preferable as the rinsing liquid, but the rinsing step can be omitted if flushing is not necessary.

[0093] <Drying step> After the above rinsing step, a drying step may be provided. The conditions of the drying step are not particularly limited and can usually be set at 70 to 150 °C for about 1 to 30 minutes. As the drying method, general methods such as heat drying using an infrared heater or an oven, hot air drying using a hot air dryer, or microwave heating drying can be used.

[0094] <<Applications>> This film and this release film can be suitably used for various release and process applications, preferably as process papers related to electronic components. More specifically, they can be suitably used as a release film for forming a green sheet of a multilayer ceramic capacitor, a separator for a liquid crystal polarizing plate, for a dry film resist, and for releasing an interlayer insulating resin. Among the above applications, due to their excellent recyclability and surface smoothness, they are more preferably used in the manufacturing process of multilayer ceramic capacitors.

[0095] In the future, in multilayer ceramic capacitors for automobiles where electrification is progressing, with the miniaturization and high capacitance of the capacitors, the thinning of the green sheets used will progress, and it is expected that the usage amount of the release film will further increase. Therefore, it is even more preferable to use this film and this release film, which are excellent in recyclability, in the manufacturing process of multilayer ceramic capacitors for automobiles.

[0096] <<Explanation of terms>> In the present invention, when referring to a "film", it includes a "sheet", and when referring to a "sheet", it includes a "film". In the present invention, when described as "X to Y" (X and Y are arbitrary numbers), unless otherwise specified, it includes the meaning of "X or more and Y or less" as well as the meaning of "preferably greater than X" or "preferably less than Y". Also, when described as "X or more" (X is an arbitrary number), unless otherwise specified, it includes the meaning of "preferably greater than X", and when described as "Y or less" (Y is an arbitrary number), unless otherwise specified, it also includes the meaning of "preferably less than Y".

Examples

[0097] Hereinafter, the present invention will be described in more detail by way of examples. However, the present invention is not limited to the following examples as long as the gist thereof is not exceeded.

[0098] <Evaluation Method> (1) Measurement of average particle size The particle size (d50) at the integrated volume fraction of 50% in the equivalent spherical distribution measured using a centrifugal sedimentation type particle size distribution measuring device (SA-CP3 type) manufactured by Shimadzu Corporation was defined as the average particle size.

[0099] (2) Arithmetic mean roughness (Ra) and maximum protrusion height (Rp) The surface arithmetic mean roughness of the polyester film, the easily soluble resin layer, and the release layer was determined as follows using a surface roughness measuring instrument (SE-3500) manufactured by Kosaka Laboratory Ltd. That is, when a portion with a reference length L (2.5 mm) in the direction of the center line was extracted from the film cross-sectional curve obtained by measurement, and the center line of this extracted portion was the x-axis and the direction of the vertical magnification was the y-axis, and represented by the roughness curve y = f(x), the surface arithmetic mean roughness was the value represented by the following formula in [nm]. The arithmetic mean roughness was obtained by obtaining 10 roughness curves from the surface of the sample film, and was represented by the average value of the arithmetic mean roughness of the extracted portions obtained from these roughness curves. The tip radius of the stylus was 2 μm, the load was 30 mg, and the cut-off value was 0.08 mm.

[0100]

Number

[0101] Further, the maximum surface protrusion height of the polyester film, the easily soluble resin layer, and the release layer represents the maximum value of the height from the average plane of the film cross-sectional curve obtained by the above method.

[0102] (3) Thickness of the easily soluble resin layer Using a scanning electron microscope (S-3400N) manufactured by Hitachi High-Technologies Corporation, the cross-section of the film was observed at a magnification of 10,000 times to measure the thickness of the easily soluble resin layer.

[0103] (4) Release layer removal rate Regarding the release films obtained in the examples and comparative examples, the following evaluations were performed. A release film (3 cm × 4 cm) having a silicone release layer was washed using a cleaning agent, and quantitative analysis of Si element was performed on the surface of the washed release film using a fluorescent X-ray analyzer (XRF, "EDX-8000" manufactured by Shimadzu Corporation). In this evaluation, the removal rate of the release layer was calculated by setting the Si element amount on the surface of the release film before washing to 100% and the Si element amount of the plain film without the release layer of the release film to 0%, and evaluated according to the following criteria. Removal of the release layer was performed by immersing the release film in a cleaning tank containing 30 mL of the cleaning agent. Using water as the cleaning agent, the release film was washed at 90°C for 2 minutes. 〇 (good); removal rate 90 - 100% × (poor); removal rate 0 - 90%

[0104] [Materials used] [Polyester film] (1) Polyethylene terephthalate film D (thickness 38 μm, Ra 01 = Ra 02 = 35 nm, Rp 01 = Rp 02 = 180 nm) (2) Polyethylene terephthalate film E (thickness 31 μm, Ra 01 = Ra 02=23 nm, Rp 01 =Rp 02 =148 nm) (3) Polyethylene terephthalate film F (thickness 31 μm, Ra 01 =Ra 02 =13 nm, Rp 01 =Rp 02 =95 nm)

[0105] [Easily soluble resin layer] Polyester raw material Dicarboxylic acid component; (A): 64.7 mol% of terephthalic acid, (B): 5.2 mol% of sodium 5-sulfoisophthalate, (C): 30.1 mol% of isophthalic acid Diol component; 88.4 mol% of ethylene glycol, 11.6 mol% of diethylene glycol

[0106] (Example 1) An 8% by mass aqueous solution of the above polyester raw material was applied onto a polyethylene terephthalate film D so that the dry film thickness became 575 nm, and heated at 100 °C for 3 minutes and at 170 °C for 15 seconds using an oven to obtain a release laminated polyester film having an easily soluble resin layer. The properties of the obtained release laminated polyester film were evaluated by the above method. The evaluation results are shown in Table 1. Furthermore, on the easily soluble resin layer of the obtained release laminated polyester film, 1.6% by mass of a curable silicone resin (15% diluted product of "KS-847H" manufactured by Shin-Etsu Chemical Co., Ltd.), 0.001% by mass of an addition type platinum catalyst ("PL-50T" manufactured by Shin-Etsu Chemical Co., Ltd.), 19.7% by mass of methyl ethyl ketone, 39.4% by mass of toluene and 39.3% by mass of heptane were mixed, and a silicone release agent was applied so that the coating amount of the release layer after drying became 0.1 g / m 2 and heated at 150 °C for 30 seconds using an oven to obtain a release film. The properties of the obtained release film were evaluated by the above method. The evaluation results are shown in Table 1.

[0107] (Examples 2 to 6) A release laminated polyester film was obtained in the same manner as in Example 1, except that the polyester film described in Table 1 below was used and the aqueous solution concentration and thickness of the easily soluble resin layer were those described in Table 1 below. Furthermore, a release layer was provided on the easily soluble resin layer of the release laminated polyester film obtained in each Example in the same manner as in Example 1 to obtain a release film. The evaluation results are shown in Table 1.

[0108] (Comparative Example 1) On a polyethylene terephthalate film D, 1.6% by mass of a curable silicone resin (15% diluted product of "KS-847H" manufactured by Shin-Etsu Chemical Co., Ltd.), 0.001% by mass of an addition-type platinum catalyst ("PL-50T" manufactured by Shin-Etsu Chemical Co., Ltd.), 19.7% by mass of methyl ethyl ketone, 39.4% by mass of toluene, and 39.3% by mass of heptane were mixed, and the silicone release agent was applied so that the coating amount of the release layer after drying was 0.1 g / m 2 and heated at 150 °C for 30 seconds using an oven to obtain a release film. The characteristics of the obtained release film were evaluated by the above method. The evaluation results are shown in Table 1.

[0109] (Comparative Examples 2 to 3) A release film was obtained in the same manner as in Comparative Example 1, except that the polyester film described in Table 1 below was used. The evaluation results are shown in Table 1.

[0110]

Table 1

[0111] As shown in the Examples, it can be seen that the release laminated polyester film of the present invention is excellent in recyclability and surface smoothness. In addition, when a release layer is provided on the easily soluble resin layer, it can be seen that the unevenness remaining on the easily soluble resin layer can be more accurately filled, and as a result, further high smoothness of the release layer surface is achieved. It is clear that the release film of the present invention can separate and remove the release layer together with the easily soluble resin layer by washing with a cleaning agent, and the polyester film can be recovered.

[0112] On the other hand, as shown in the comparative example, when a release layer is laminated on a polyester film without an easily soluble resin layer, it can be seen that not only is the surface smoothness insufficient, but the release layer cannot be separated and removed.

Industrial Applicability

[0113] According to the release laminated polyester film of the present invention, by having an easily soluble resin layer on one side of the polyester film, the unevenness of the polyester film can be preferably filled, and the surface smoothness is excellent. In addition, the release film of the present invention having a release layer provided on the easily soluble resin layer achieves further high smoothness. Further, after using the release film, the release layer can be easily separated and removed by dissolving the easily soluble resin layer using a cleaning agent, and the polyester film can be recovered. Therefore, since the release laminated polyester film and the release film of the present invention are excellent in recyclability and surface smoothness, they can be preferably used for various release and process applications, especially in the manufacturing process of laminated ceramic capacitors.

Explanation of Reference Numerals

[0114] 1 Release laminated polyester film 2 Release film 11 Polyester film 12 Easily soluble resin layer 13 Release layer

Claims

1. A release laminated polyester film having a readily soluble resin layer on one surface of the polyester film, wherein the readily soluble resin layer contains a polyester component, and the polyester component contains, as acid components, (A) terephthalic acid, (B) a dicarboxylic acid having a sulfonate group, and (C) other dicarboxylic acids, in the readily soluble resin layer, the content ratio of the component (B) in all acid components is 8 mol% or less, and the content ratio of the component (C) in all acid components is 18 mol% or more, the component (C) contains at least isophthalic acid, The arithmetic mean roughness Ra of the surface of the readily soluble resin layer １ is 30 nm or less, and the maximum protrusion height Rp １ is 150 nm or less. A release laminated polyester film.

2. A release laminated polyester film having a readily soluble resin layer on one surface of the polyester film, wherein the readily soluble resin layer contains a polyester component, and the polyester component contains, as acid components, (A) terephthalic acid, (B) a dicarboxylic acid having a sulfonate group, and (C) other dicarboxylic acids, in the readily soluble resin layer, the content ratio of the component (B) in all acid components is 8 mol% or less, and the content ratio of the component (C) in all acid components is 18 mol% or more, the glass transition temperature of the readily soluble resin layer is 50°C or higher and 85°C or lower, the arithmetic mean roughness Ra 1 of the surface of the readily soluble resin layer is 30 nm or less, and the maximum protrusion height Rp 1 is 150 nm or less, A release laminated polyester film.

3. The release laminated polyester film according to claim 1 or 2, wherein the component (B) contains at least sodium 5-sulfoisophthalate.

4. The release laminated polyester film according to claim 2 or 3, wherein the component (C) contains at least isophthalic acid.

5. The release laminated polyester film according to any one of claims 1, 3, and 4, wherein the glass transition temperature of the readily soluble resin layer is 50°C or higher and 85°C or lower.

6. The release laminated polyester film according to any one of claims 1 to 5, wherein the content ratio of the component (A) in all acid components in the readily soluble resin layer is 75 mol% or less.

7. The maximum protrusion height Rp on the surface of the readily soluble resin layer １ The release laminated polyester film according to any one of claims 1 to 6, wherein the maximum protrusion height Rp is 10 nm or more.

8. The maximum protrusion height Rp on the surface of the readily soluble resin layer １ (nm) and the ratio (Rp １ / t) of the thickness t (nm) of the readily soluble resin layer is 0.01 to 0.

25. The release laminated polyester film according to any one of claims 1 to 7.

9. The release laminated polyester film according to any one of claims 1 to 8, which is used in the manufacturing process of a multilayer ceramic capacitor.

10. A release film having a release layer on the readily soluble resin layer of the release laminated polyester film according to any one of claims 1 to 9.

11. The arithmetic mean roughness Ra of the surface of the release layer ２ The release film according to claim 10, wherein the arithmetic mean roughness Ra of the surface of the release layer is 30 nm or less.

12. The maximum protrusion height Rp of the surface of the release layer ２ The release film according to claim 10 or 11, wherein the maximum protrusion height Rp is 125 nm or less.

13. The release film according to any one of claims 10 to 12, which is used in the manufacturing process of the multilayer ceramic capacitor.

14. A release layer removing method including a release layer removing step of washing the release film according to any one of claims 10 to 13 with a cleaning agent to remove the release layer from the polyester film together with the easily soluble resin layer.

15. The release layer removing method according to claim 14, wherein the cleaning agent is water.

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