WO2023027033A1

WO2023027033A1 - Polyester film, polyester film manufacturing method, and release film

Info

Publication number: WO2023027033A1
Application number: PCT/JP2022/031594
Authority: WO
Inventors: 一仁宮宅; 泰雄江夏; 悠樹豊嶋
Original assignee: 富士フイルム株式会社
Priority date: 2021-08-26
Filing date: 2022-08-22
Publication date: 2023-03-02
Also published as: JPWO2023027033A1; KR20240022660A

Abstract

The purpose of the present invention is to provide a polyester film which enables manufacturing a ceramic green sheet that suppresses the occurrence of unevenness defects in the case of using a release film obtained using the polyester film to manufacture the ceramic green sheet; and to provide a manufacturing method of the polyester film. A further purpose of the present invention is to provide a release film.　This polyester film is provided with a resin layer and a polyester substrate, has a first main surface and a second main surface, and the second main surface is one side of the resin layer; the resin layer has protrusions on the surface that is the second main surface, and is used to manufacture the release film by forming a release layer is on the first main surface, wherein the polyester film satisfies condition A. Condition A: when observing the second main surface using a scanning electron microscope, and selecting the protrusion with the longest longitudinal radius, the ratio A of the height of the protrusion to the long diameter of the protrusion is less than or equal to 0.7.

Description

POLYESTER FILM, POLYESTER FILM MANUFACTURING METHOD, RELEASE FILM

The present invention relates to a polyester film, a method for producing a polyester film, and a release film.

　Biaxially oriented polyester films are used in a wide range of applications in terms of workability, mechanical properties, electrical properties, dimensional stability, transparency, and chemical resistance. For example, a release film obtained by laminating a release layer on the surface of a biaxially oriented polyester film is used to produce a ceramic green sheet for manufacturing a laminated ceramic capacitor.

For example, in Patent Document 1, a polyester film containing substantially no inorganic particles is used as a base material, a release coating layer is provided on one surface of the base material, and particles are provided on the other surface. A release film for producing a ceramic green sheet is disclosed, which has a specific easy-to-slip coating layer containing

WO2019/039264

With the recent increase in capacity and miniaturization of ceramic capacitors, there is a demand for even thinner ceramic green sheets. On the other hand, it is considered that the more the thickness of the ceramic green sheet is reduced, the greater the influence of the surface shape of the release film on the performance of the ceramic green sheet. For example, if the release surface of the release film has an uneven shape, the uneven shape may be transferred to the ceramic green sheet, causing the thickness of the ceramic green sheet to fluctuate and possibly deteriorating the performance of the ceramic capacitor product.

The present inventors have further studied the release film used in the production of the ceramic green sheet with reference to the technique described in Patent Document 1, and found that not only the release surface of the release film but also the surface opposite to the release surface It has been found that the properties of the conveying surface, which is, may also affect the performance of the ceramic sheet. More specifically, in the polyester film used for the production of the release film, the surface opposite to the surface on which the release layer is formed is used for the purpose of improving windability and suppressing wrinkles during high-speed transportation of the polyester film and / or release film. By providing a layer containing particles on the surface of the substrate, a conveying surface having a projection shape is often formed. The present inventors have found that when a polyester film or a release film having such a transport surface is transported at high speed, the release surface of the release film may become uneven. When a release film having such an uneven shape on the release surface is used in the production of a ceramic green sheet, fine recesses or protrusions are generated in the ceramic green sheet. It has been found that there is room for further improvement in the production of
In addition, below, a micro recessed part and a convex part are generically called an "unevenness|corrugation defect."

In view of the above-mentioned circumstances, the present invention provides a polyester film and a polyester that can produce a ceramic green sheet in which the occurrence of uneven defects is suppressed when a release film obtained using a polyester film is used for producing a ceramic green sheet. An object of the present invention is to provide a film manufacturing method.
Another object of the present invention is to provide a release film.

As a result of intensive studies aimed at solving the above problems, the inventors found that the above problems can be solved with the following configuration.

[1] It comprises a resin layer and a polyester base material, and has a first principal surface and a second principal surface, the second principal surface being one of the surfaces of the resin layer, and the resin layer comprising: A polyester film having protrusions on the surface that is the second main surface and used for producing a release film by forming a release layer on the first main surface, the polyester film satisfying requirement A described later. Polyester the film.
[2] The polyester film of [1], wherein the projections are formed of organic particles.
[3] The polyester film of [1] or [2], wherein the release film is a release film for producing a ceramic green sheet.
[4] The polyester film of [2], wherein the organic particles contain at least one selected from the group consisting of styrene resins and urethane resins.
[5] The polyester film according to any one of [1] to [4], wherein the second main surface has a surface free energy of 25 to 45 mJ/m ² .
[6] The polyester film according to any one of [1] to [5], wherein the resin layer contains at least one binder selected from the group consisting of acrylic resins, urethane resins and olefin resins.
[7] Using a scanning electron microscope, an area of 10000 μm ² on the second main surface is observed, and non-contact surface profile measurement is performed using an optical interferometer on the protrusion having the longest major axis in the area. The polyester film according to any one of [1] to [6], wherein the projection height obtained by the process is 0.3 μm or more.
[8] The polyester film according to any one of [1] to [7], wherein the polyester film has a thickness of 40 μm or less.
[9] The polyester film according to any one of [1] to [8], wherein the resin layer has a thickness of 1 to 500 nm.
[10] The method for producing a polyester film according to any one of [1] to [9], wherein step 1 of preparing a uniaxially oriented film by longitudinally stretching an unstretched polyester film having a polyester substrate. A step 2 of forming a resin layer on the surface of the uniaxially oriented film using a composition containing organic particles, and a step 3 of stretching in the width direction while heating the uniaxially oriented film having the resin layer. , wherein X is the lowest temperature among the temperature of the endothermic peak and the temperature of the baseline shift appearing in the curve showing the change in the amount of heat obtained by measuring the organic particles with a differential scanning calorimeter; A method for producing a polyester film, wherein X is lower than Y, where Y is the surface temperature of the uniaxially oriented film.
[11] The method for producing a polyester film according to [10], wherein the organic particles satisfy at least one of

requirements

1 and 2 below. Requirement 1: The glass transition temperature of the organic particles is 40° C. or lower. Requirement 2: The melting point of the organic particles is 110° C. or less.
[12] A release film comprising the polyester film according to any one of [1] to [9] and a release layer.

According to the present invention, when a release film obtained using a polyester film is used for manufacturing a ceramic green sheet, a ceramic green sheet in which the occurrence of irregularities is suppressed can be manufactured, and a method for manufacturing a polyester film. can provide Moreover, according to this invention, a peeling film can be provided.

It is an observation image of the surface of the polyester film of the present invention produced in Examples. It is an observation image of the surface of the biaxially oriented film produced in the comparative example. BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing which shows an example of a structure of the polyester film of this invention.

Hereinafter, embodiments of the present invention will be described in detail. It should be noted that the present invention is not limited to the following embodiments, and can be implemented with appropriate modifications within the scope of the purpose of the present invention.

In this specification, a numerical range represented by "to" means a range including the numerical values before and after "to" as lower and upper limits. In the numerical ranges described stepwise in this specification, the upper limit or lower limit described in a certain numerical range may be replaced with the upper limit or lower limit of another numerical range described stepwise. Moreover, in the numerical ranges described in this specification, the upper limit or lower limit described in a certain numerical range may be replaced with the values shown in the examples.
As used herein, the amount of each component in the composition means the total amount of the multiple substances present in the composition unless otherwise specified when there are multiple substances corresponding to each component in the composition. do.
In this specification, the term "step" includes not only independent steps, but also if the intended purpose of the step is achieved even if it cannot be clearly distinguished from other steps. be
In this specification, a combination of two or more preferred aspects is a more preferred aspect.

As used herein, the term "longitudinal direction" means the longitudinal direction of the polyester film during the production of the polyester film, and is synonymous with the "conveyance direction" and the "machine direction."
As used herein, "width direction" means a direction perpendicular to the longitudinal direction. In this specification, "perpendicular" is not limited to strictly perpendicular, but includes substantially perpendicular. The term “substantially orthogonal” means intersecting within the range of 90°±5°, preferably intersecting within the range of 90°±3°, more preferably intersecting within the range of 90°±1°. .
As used herein, the term "major axis" means the longest diameter of the projections in the in-plane direction when the projections present on the surface (second main surface) of the polyester film or release film are observed.

[Polyester film]
The structure of the polyester film of the present invention (hereinafter also referred to as "this film") will be described with reference to the drawings.
FIG. 3 is a cross-sectional view showing an example of the structure of this film. The polyester film 1 of the present invention includes a resin layer 2 and a polyester base material 3, and has a first main surface 4 and a second main surface 5, the second main surface 5 being the surface of the resin layer 2. On the other hand, the resin layer 2 is a polyester film which has projections 6 on the surface which is the second main surface 5 and which is used to form a release layer on the first main surface 4 to produce a release film. Moreover, this film satisfies the following requirement A.
Requirement A: Observing a region with an area of 10000 μm ² on the second main surface using a scanning electron microscope, and selecting a protrusion with the longest major axis in the above region, the selected selected measured using a scanning electron microscope The ratio A of the height of the selected protrusions measured by non-contact surface profilometry using an optical interferometer to the major diameter of the selected protrusions is 0.7 or less.
In this specification, of the two opposing main surfaces of the polyester film, the main surface on which the release layer is formed is referred to as the "first main surface", and the surface opposite to the polyester substrate of the resin layer The configured principal surface is referred to as a "second principal surface".

By using the release film obtained using this film in the production of a ceramic green sheet, a ceramic green sheet in which the occurrence of unevenness defects is suppressed can be obtained. Although the details of the reason why the effect of suppressing the occurrence of uneven defects in the ceramic green sheet (hereinafter also referred to as "the effect of the present invention") can be obtained by the present film having the above structure are not clear, the present invention The inventors generally presume as follows.
As described above, in the case of producing a release film using a polyester film having a layer containing particles on the surface opposite to the surface forming the release layer, the polyester film and/or the release film are transported under high-speed transport conditions. It is considered that the particles tend to drop off on the conveying surface due to the impact caused by the contact with the conveying roll. Thereafter, for example, when the release film is wound into a roll or stacked and stored, the conveying surface and the peeling surface come into contact with each other, and particles drop off from the conveying surface and migrate to the peeling surface. Such particles form fine irregularities on the peeling surface of the release film forming the ceramic green sheet, and the irregularities are transferred to the ceramic green sheet, resulting in uneven defects in the ceramic green sheet. It is speculated that
To address this problem, the present film is characterized in that the projections present on the second main surface, which is the conveying surface of the release film, are projections having a ratio of height to length within a predetermined range. It is presumed that, even during high-speed transportation, the substances constituting the protrusions on the transportation surface are less likely to come off, thereby suppressing the transfer of contaminants to the peeling surface. As a result, it is thought that the generation of unevenness defects in the ceramic green sheets could be suppressed.

〔composition〕
The structure of this film will be described below.
The film has at least a resin layer and a polyester base material.
Of the two main surfaces of the polyester film, the first main surface is a surface for forming a release layer, which will be described later. That is, after manufacturing the polyester film, a release film having the polyester film and the release layer is produced by laminating the release layer on the first main surface.
Of the two main surfaces of the polyester film, the second main surface opposite to the first main surface is one surface of the resin layer. That is, the resin layer constitutes the outermost layer of the polyester film.

The present film has at least the above resin layer and polyester base material, and is not limited to those having the above configuration as long as the above requirement A is satisfied.
For example, the film may have a primer layer or the like between the resin layer and the polyester base material.

Below, each layer of this film will be described in detail.

<Resin layer>
A resin layer is formed on one side of the polyester substrate. The surface of the resin layer opposite to the surface facing the polyester base constitutes the second main surface. Moreover, protrusions are formed on the surface of the resin layer, which is the second main surface.
By having the resin layer, the present film can improve the transportability of the polyester film and the release film. More specifically, even during high-speed transport, the film has excellent winding quality, suppresses the occurrence of scratches and defects, and reduces transport wrinkles.

The resin layer may be provided directly on the surface of the polyester base material, or may be provided on the surface of the polyester base material via another layer. is preferred.

The resin layer is not particularly limited as long as it is a layered member having projections on at least one surface, but it preferably contains a binder. As the binder contained in the resin layer, non-polyester resins other than polyester resins are preferable. Moreover, the resin layer may contain additives other than the substance constituting the projections and the non-polyester resin.
In this specification, the term "binder" means a component containing a resin other than the substance that constitutes the protrusions.

(protrude)
The substance constituting the projections is not particularly limited, and may be of one type alone or in combination of two or more types. Also, the substance constituting the projections may be the same as or different from the binder.

The protrusions present on the surface of the resin layer include, for example, protrusions formed by particles described later, and the effect of the present invention is more excellent, and the polyester film that satisfies the requirement A can be more easily produced. , protrusions formed by organic particles are preferred. Although the details of the mechanism by which the effect of the present invention is further improved when the projections are formed of organic particles are not clear, when the film contacts the object to be contacted on the second main surface, the deformation of the projections causes Since the force received by the projections is absorbed, even during high-speed transportation, the substances that make up the projections are less likely to fall off from the conveying surface, suppressing the transfer of contaminants to the peeling surface, and eliminating uneven defects in the ceramic green sheet. It is presumed that the occurrence of
Resin particles are preferable as the organic particles. Examples of resins constituting resin particles include styrene resins, urethane resins, acrylic resins, polyester resins, and silicone resins. Among them, the organic particles preferably contain at least one selected from the group consisting of styrene resins, acrylic resins, and urethane resins, in that a polyester film that satisfies Requirement A can be more easily produced. And it is more preferable to include at least one selected from the group consisting of urethane resins.

As used herein, a styrene resin means a resin containing structural units derived from styrene.
Examples of the styrene resin constituting the resin particles include a homopolymer consisting of styrene only, and a styrene copolymer such as a styrene-acrylic copolymer containing a structural unit derived from styrene and a structural unit derived from acrylate or methacrylate. be done.
The urethane resin constituting the resin particles is not limited as long as it is a polymer having a urethane bond, and known urethane resins such as reaction products of isocyanate compounds and polyol compounds can be used.
Moreover, in this specification, acrylic resin means a resin containing structural units derived from acrylate or methacrylate.

The resin particles may be crosslinked particles having a crosslinked structure or non-crosslinked particles having no crosslinked structure. Examples of the crosslinked particles include crosslinked urethane resin particles composed of a urethane resin having a crosslinked structure. Non-crosslinked particles include, for example, non-crosslinked styrene resin particles composed of non-crosslinked styrene resin.

Regarding organic particles, when the lowest temperature among the temperature of the endothermic peak and the temperature of the baseline shift appearing in the curve (DSC curve) showing the change in the amount of heat obtained by measuring the organic particles with a differential scanning calorimeter is X Furthermore, the temperature X is preferably 120° C. or lower, more preferably 115° C. or lower, and even more preferably 110° C. or lower. Although the lower limit is not particularly limited, it is, for example, -40°C or higher in that the effect of suppressing blocking of the polyester film is more excellent.

The temperature X of the organic particles is measured using a differential scanning calorimeter (for example, "DSC-60aPlus" manufactured by Shimadzu Corporation). Specifically, the organic particles are placed in a closed pan of a differential scanning calorimeter, measured at a heating rate of 5 ° C./min in the range of -40 to 120 ° C., and a curve showing the endothermic heat of the obtained organic particles (DSC curve ) and the temperature at which the baseline shifts (shift temperature), the temperature X is the lowest temperature.
Here, the temperature of the baseline shift is the point of intersection of a straight line obtained by extending the baseline on the low temperature side to the high temperature side in the DSC curve and a tangent line drawn at the point where the gradient of the curve portion that changes stepwise becomes maximum. Calculated as temperature.

Examples of commercially available styrene resin particles include Nipol (registered trademark) UFN1008 (manufactured by Nippon Zeon Co., Ltd.).
Examples of commercial products of urethane resin particles include Artpearl (registered trademark) C-1000T and MM110SMA (manufactured by Negami Kogyo Co., Ltd.).

(binder)
It is preferable that the resin layer contains a non-polyester resin as a binder, because the effect of suppressing unevenness defects during long-term storage is excellent.
The non-polyester resin contained as a binder in the resin layer is not particularly limited as long as it is a resin other than a polyester resin. acrylic resin, urethane resin, or olefin resin is preferable, and urethane resin is more preferable, because the effect of is more excellent.
Here, acrylic resins and olefin resins and polyester resins do not have sufficient compatibility with each other, so it is speculated that foreign matter due to impurities such as oligomers that precipitate from the polyester resin will not occur even after long-term storage. ing. Among urethane resins, highly hydrophobic urethane resins (that is, urethane resins whose SP value is sufficiently different from that of polyester resins) also suffer from uneven defects during long-term storage for the same reason as acrylic resins and olefin resins. can be suppressed.
The acrylic resin, olefin resin, and urethane resin are not particularly limited, and known resins can be used.

The olefin resin may be any resin containing a structural unit derived from an olefin in its main chain. The olefin is not particularly limited, but is preferably an alkene having 2 to 6 carbon atoms, more preferably ethylene, propylene or hexene, and still more preferably ethylene.
The olefin-derived structural units contained in the olefin resin are preferably 50 to 99 mol %, more preferably 60 to 98 mol %, based on all the structural units of the olefin resin.

As the olefin resin, an acid-modified olefin resin is preferable because it can prevent electrification when the release layer is applied. Acid-modified olefin resins include, for example, copolymers obtained by modifying the above olefin resins with an acid-modifying component such as an unsaturated carboxylic acid or an anhydride thereof.
Examples of acid-modified components include acrylic acid, methacrylic acid, maleic acid, maleic anhydride, itaconic acid, itaconic anhydride, fumaric acid, and crotonic acid, and half esters and half amides of unsaturated dicarboxylic acids. Among them, acrylic acid, methacrylic acid, maleic acid, or maleic anhydride is preferable from the viewpoint of the dispersion stability of the resin.

Examples of the acidic group contained in the acid-modified olefin resin include a carboxyl group, a sulfo group, and a phosphoric acid group, which are acidic groups corresponding to the acid-modified components described above, and a carboxyl group is preferred. The acidic group may form an acid anhydride, or may be neutralized with at least one selected from alkali metals, organic amines and ammonia.
The acid-modified olefin resin may contain only one type of structural unit having an acidic group, or may contain two or more types.

Commercially available acid-modified olefin resins include, for example, Zaixen (registered trademark) series such as Zaixen AC, A, L, NC, and N (manufactured by Sumitomo Seika Co., Ltd.), Chemipearl S100, S120, S200, S300, and S650. , Chemipearl (registered trademark) series such as SA100 (manufactured by Mitsui Chemicals, Inc.), and Hitech S3121, S3148K (manufactured by Toho Chemical Co., Ltd.), Arrow Base SE-1013, SE- 1010, SB-1200, SD-1200, SD-1200, DA-1010, DB-4010, etc. Arrowbase (registered trademark) series (manufactured by Unitika Ltd.), Hardren AP-2, NZ-1004, NZ-1005 (manufactured by Toyobo Co., Ltd.), Sepulsion G315, and VA407 (manufactured by Sumitomo Seika Co., Ltd.).
Acid-modified olefin resins described in [0022] to [0034] of JP-A-2014-076632 can also be preferably used.

The acrylic resin is a resin containing structural units derived from (meth)acrylate, and may be copolymerized with a vinyl monomer such as styrene. Although the acrylic resin is not particularly limited, it preferably contains a structural unit derived from a (meth)acrylate having an alkyl group having 1 to 12 carbon atoms, and a (meth)acrylate having an alkyl group having 1 to 8 carbon atoms. It is more preferable to contain structural units derived from.
The acrylic resin preferably contains an acid-modified component in order to prevent electrification when the release layer is applied. The acrylic resin preferably contains a structural unit derived from (meth)acrylic acid as an acid-modified component. (Meth)acrylic acid may form an acid anhydride, or may be neutralized with at least one selected from alkali metals, organic amines and ammonia.
When an aqueous acrylic resin dispersion is used for the production of the resin layer, an aqueous dispersion containing an acrylic resin and a dispersing agent can be preferably used.
The (meth)acrylate-derived structural units contained in the acrylic resin preferably account for 50 to 100 mol % of all the structural units of the acrylic resin.
The acid value of the acrylic resin is preferably 30 mgKOH/g or less, more preferably 20 mgKOH/g or less. The lower limit of the acid value is not particularly limited, and is, for example, 0 mgKOH/g, but is preferably 2 mgKOH/g or more from the viewpoint of coating as an aqueous dispersion.
When using an acrylic resin whose solubility parameter (SP value) is different from that of the polyester resin, the compatibility between the acrylic resin and the polyester resin is insufficient, and as a result, the effect of suppressing uneven defects during long-term storage is more improved. can be improved. Such an acrylic resin, for example, to have an acid value within the above range, and to contain a structural unit derived from a (meth)acrylate having an alkyl group having 1 to 12 carbon atoms, so as to satisfy at least one of can be obtained by adjusting to

The urethane resin is not limited as long as it is a polymer having a urethane bond, and known urethane resins such as reaction products of isocyanate compounds and polyol compounds can be used.
When an aqueous dispersion containing a urethane resin is used to produce the resin layer, the aqueous dispersion preferably contains a urethane resin having an acidic group (for example, a carboxyl group), or contains a urethane resin and a dispersant. Thereby, the film formability of the resin layer is improved.
The urethane resin has, for example, at least the structure of the raw material polyol compound, the hydrophobicity or hydrophilicity of the raw material polyol, the structure of the raw material isocyanate compound, and the hydrophobicity or hydrophilicity of the raw material isocyanate compound. By adjusting one, the desired SP value can be obtained. In this way, by using a urethane resin adjusted to be highly hydrophobic, the compatibility between the urethane resin and the polyester resin becomes insufficient, and as a result, the effect of suppressing uneven defects during long-term storage. can be further improved.
Among urethane resins, urethane resins having a polyester structure (polyester-based urethane resins) are preferred because they are highly hydrophobic and can further improve the effect of suppressing uneven defects during long-term storage.

Commercially available urethane resins include, for example, Hydran (registered trademark) AP-40N, HW-312B, and HW-350 (manufactured by DIC Corporation), Takelac (registered trademark) W-5030, and W- 6020 (manufactured by Mitsui Chemicals, Inc.), ADEKA BONTITER (registered trademark) HUX-524 (manufactured by ADEKA Corporation), and Superflex (registered trademark) 210 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.).

The resin layer may contain a single non-polyester resin as a binder, or may contain two or more non-polyester resins.
The content of the binder in the resin layer is preferably 30 to 99.8% by mass, more preferably 50 to 99.5% by mass, based on the total mass of the resin layer, in order to further suppress uneven defects in the ceramic green sheet. preferable.

(Additive)
The resin layer may contain additives other than the substance constituting the projections and the binder.
Additives contained in the resin layer include, for example, surfactant waxes, dispersants, antioxidants, ultraviolet absorbers, colorants, reinforcing agents, plasticizers, antistatic agents, flame retardants, rust inhibitors, and Examples include antifungal agents.

The resin layer preferably contains a surfactant from the viewpoint of improving the smoothness of areas other than areas where projections are present on the second main surface. The smoothness of the above region of the second main surface is improved, and the surface roughness of the second main surface is reduced by factors other than the presence of protrusions, so that the ratio A of the second main surface and the protrusion height described later are included. By controlling the physical properties within the desired range, the effects of the present invention can be improved.

The surfactant is not particularly limited, and includes silicone-based surfactants, fluorine-based surfactants, and hydrocarbon-based surfactants. A hydrocarbon-based surfactant is preferable because it can suppress charging on the second main surface.

The silicone-based surfactant is not particularly limited as long as it has a silicon-containing group as a hydrophobic group, and examples thereof include polydimethylsiloxane, polyether-modified polydimethylsiloxane, and polymethylalkylsiloxane.
Examples of commercially available silicone surfactants include BYK (registered trademark)-306, BYK-307, BYK-333, BYK-341, BYK-345, BYK-346, BYK-347, BYK-348, and , BYK-349 (manufactured by BYK), and KF-351A, KF-352A, KF-353, KF-354L, KF-355A, KF-615A, KF-945, KF-640, KF-642, KF-643, KF-6020, X-22-4515, KF-6011, KF-6012, KF-6015, and KF-6017 (manufactured by Shin-Etsu Chemical Co., Ltd.).

The fluorosurfactant is not particularly limited as long as it has a fluorine-containing group as a hydrophobic group, and examples thereof include perfluorooctane sulfonic acid and perfluorocarboxylic acid.
Commercially available fluorosurfactants include, for example, Megafac (registered trademark) F-114, F-410, F-440, F-447, F-553, and F-556 (manufactured by DIC Corporation). ), and Surflon (registered trademark) S-211, S-221, S-231, S-233, S-241, S-242, S-243, S-420, S-661, S-651, and , and S-386 (manufactured by AGC Seimi Chemical Co., Ltd.).
In addition, from the viewpoint of improving environmental suitability, the fluorine-based surfactant has a linear perfluoroalkyl group having 7 or more carbon atoms, such as perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS). Surfactants derived from substitute materials for compounds are preferred.

Hydrocarbon surfactants include, for example, anionic surfactants, nonionic surfactants, cationic surfactants, and amphoteric surfactants.
Anionic surfactants include, for example, alkyl sulfates, alkyl sulfonates, alkylbenzene sulfonates, alkyl phosphates, and fatty acid salts.
Nonionic surfactants include, for example, polyalkylene glycol mono- or dialkyl ethers, polyalkylene glycol mono- or dialkyl esters, and polyalkylene glycol mono-alkyl esters/mono-alkyl ethers.
Cationic surfactants include primary to tertiary alkylamine salts and quaternary ammonium compounds.
Amphoteric surfactants include surfactants having both an anionic site and a cationic site in the molecule.

Commercially available anionic surfactants include, for example, RAPISOL (registered trademark) A-90, A-80, BW-30, B-90, and C-70 (manufactured by NOF Corporation), NIKKOL (registered trademark) OTP-100 (manufactured by Nikko Chemical Co., Ltd.), Kohakul (registered trademark) ON, L-40, and Phosphanol (registered trademark) 702 (manufactured by Toho Chemical Industry Co., Ltd.) ), and Viewlite (registered trademark) A-5000 and SSS (manufactured by Sanyo Chemical Industries Co., Ltd.).
Commercially available nonionic surfactants include, for example, Naroacty (registered trademark) CL-95 and HN-100 (trade name: manufactured by Sanyo Chemical Industries, Ltd.), Resolex BW400 (trade name: KOKYU ALCOHOL KOGYO Co., Ltd.), EMALEX (registered trademark) ET-2020 (manufactured by Nippon Emulsion Co., Ltd.), and Surfynol (registered trademark) 104E, 420, 440, 465, and Dynol (registered trademark) 604, 607 (manufactured by Nissin Chemical Industry Co., Ltd.).

As the hydrocarbon surfactant, at least one of an anionic surfactant and a nonionic surfactant is preferable in that a coating layer having a smooth surface can be formed without hindering the dispersion of the resin. agents are more preferred. That is, as the surfactant, an anionic hydrocarbon-based surfactant is more preferable in terms of improving surface smoothness.

The anionic hydrocarbon-based surfactant preferably has a plurality of hydrophobic terminal groups in terms of further improving smoothness. The hydrophobic end group may be part of the hydrocarbon group of the hydrocarbon surfactant. For example, a hydrocarbon surfactant terminated with a hydrocarbon group having a branched chain structure will have a plurality of hydrophobic end groups.
Examples of anionic hydrocarbon surfactants having multiple hydrophobic terminal groups include di-2-ethylhexyl sodium sulfosuccinate (having four hydrophobic terminal groups), di-2-ethyloctyl sodium sulfosuccinate ( 4 hydrophobic end groups) and branched alkyl benzene sulfonates (2 hydrophobic end groups).

One type of surfactant may be used, or two or more types may be used in combination.
The content of the surfactant is preferably 0.1 to 10% by mass with respect to the total mass of the resin layer, more preferably 0.1 to 5% by mass in terms of better surface smoothness, and 0.5 to 2% by mass is more preferred.

The wax is not particularly limited, and may be natural wax or synthetic wax. Natural waxes include carnauba wax, candelilla wax, beeswax, montan wax, paraffin wax, and petroleum wax. In addition, a slipping agent described in [0087] of International Publication No. 2017/169844 can also be used.
The wax content is preferably 0 to 10% by mass with respect to the total mass of the resin layer.

(thickness)
The resin layer can be formed, for example, by coating a composition containing particles on one surface of the polyester substrate as described later. In that case, the thickness of the resin layer is often 1 nm to 1 μm, and is preferably 10 nm to 1 μm, more preferably 20 to 500 nm, in terms of the excellent effect of suppressing unevenness defects during long-term storage. More preferably, 20 to 200 nm is even more preferable.
Alternatively, as described later, the polyester base material and the resin used for forming the resin layer may be co-extruded. In that case, the thickness of the resin layer is often 1 to 10 μm.
The thickness of the resin layer is preferably from 1 to 500 nm, more preferably from 1 to 250 nm, even more preferably from 10 to 100 nm, and particularly preferably from 20 to 100 nm, from the viewpoints of production suitability of the resin layer and reduction of haze. .
For the thickness of the resin layer, a section having a cross section perpendicular to the main surface of the polyester film is prepared, and a scanning electron microscope (SEM: Scanning Electron Microscope) or a transmission electron microscope (TEM: Transmission Electron Microscope) is used. shall be the arithmetic mean of the five thicknesses of the section, measured at
If the resin layer is soft and it is difficult to stably produce a cross section, the measurement may be performed using a refractometer. Specifically, the film thickness of the resin layer can be determined by fitting the measured reflectance spectrum with the film thickness and refractive index of the resin layer and the polyester base material.

The method of forming the resin layer will be described in detail in the "resin layer forming process" described later.

<Polyester base material>
A polyester substrate is a film-like body containing a polyester resin as the main polymer component. Here, the "main polymer component" means the polymer with the highest content (mass) among all the polymers contained in the film.
Preferably, the polyester substrate is substantially free of particles. "Substantially free of particles" means that the content of particles is 50 mass with respect to the total mass of the polyester base material when the element derived from the particles is quantitatively analyzed by fluorescent X-ray analysis for the polyester base material. It is defined as ppm or less, preferably 10 mass ppm or less, more preferably detection limit or less. This is because even if the particles are not actively added to the polyester base material, contaminants derived from foreign substances, raw material resins, or stains attached to the lines or equipment in the manufacturing process of the polyester base material are peeled off, This is because they may be mixed into the base material. Examples of the particles include particles used for forming the resin layer described above.
The polyester base material may contain a single polyester resin, or may contain two or more polyester resins.

(polyester resin)
A polyester resin is a polymer having an ester bond in its main chain. A polyester resin is usually formed by polycondensing a dicarboxylic acid compound and a diol compound, which will be described later.
The polyester resin is not particularly limited, and known polyester resins can be used. Polyester resins include, for example, polyethylene terephthalate (PET), polyethylene-2,6-naphthalate (PEN), and copolymers thereof, with PET being preferred.

The intrinsic viscosity of the polyester resin is preferably 0.50 dl/g or more and less than 0.80 dl/g, more preferably 0.55 dl/g or more and less than 0.70 dl/g.
The melting point (Tm) of the polyester resin is preferably 220 to 270°C, more preferably 245 to 265°C.
The glass transition temperature (Tg) of the polyester resin is preferably 65-90°C, more preferably 70-85°C.

The method for producing the polyester resin is not particularly limited, and known methods can be used. For example, a polyester resin can be produced by polycondensing at least one dicarboxylic acid compound and at least one diol compound in the presence of a catalyst.

-catalyst-
The catalyst used for producing the polyester resin is not particularly limited, and any known catalyst that can be used for synthesizing the polyester resin can be used.
Examples of catalysts include alkali metal compounds (e.g., potassium compounds, sodium compounds), alkaline earth metal compounds (e.g., calcium compounds, magnesium compounds), zinc compounds, lead compounds, manganese compounds, cobalt compounds, aluminum compounds, antimony. compounds, titanium compounds, germanium compounds, and phosphorus compounds. Among them, titanium compounds are preferable from the viewpoint of catalytic activity and cost.
Only one kind of catalyst may be used, or two or more kinds thereof may be used in combination. at least one metal catalyst selected from potassium compounds, sodium compounds, calcium compounds, magnesium compounds, zinc compounds, lead compounds, manganese compounds, cobalt compounds, aluminum compounds, antimony compounds, titanium compounds, and germanium compounds; It is preferable to use a compound together, and it is more preferable to use a titanium compound and a phosphorus compound together.

As the titanium compound, an organic chelate titanium complex is preferred. An organic chelate titanium complex is a titanium compound having an organic acid as a ligand.
Organic acids include, for example, citric acid, lactic acid, trimellitic acid, and malic acid.
As the titanium compound, titanium compounds described in [0049] to [0053] of Japanese Patent No. 5575671 can also be used, and the contents of the above publications are incorporated herein.

-Dicarboxylic acid compound-
Examples of dicarboxylic acid compounds include dicarboxylic acids such as aliphatic dicarboxylic acid compounds, alicyclic dicarboxylic acid compounds, and aromatic dicarboxylic acid compounds, and dicarboxylic acids such as methyl ester compounds and ethyl ester compounds of these dicarboxylic acids. esters. Among them, aromatic dicarboxylic acid or methyl aromatic dicarboxylate is preferable.

Examples of aliphatic dicarboxylic acid compounds include malonic acid, succinic acid, glutaric acid, adipic acid, suberic acid, sebacic acid, dodecanedioic acid, dimer acid, eicosandioic acid, pimelic acid, azelaic acid, methylmalonic acid, and ethylmalonic acid.
Alicyclic dicarboxylic acid compounds include, for example, adamantanedicarboxylic acid, norbornenedicarboxylic acid, cyclohexanedicarboxylic acid, and decalinedicarboxylic acid.

Examples of aromatic dicarboxylic acid compounds include terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and 1,8-naphthalenedicarboxylic acid. , 4,4′-diphenyldicarboxylic acid, 4,4′-diphenyletherdicarboxylic acid, 5-sodium sulfoisophthalic acid, phenylindanedicarboxylic acid, anthracenedicarboxylic acid, phenanthenedicarboxylic acid, and 9,9′-bis(4- carboxyphenyl)fluoric acid.
Among them, terephthalic acid or 2,6-naphthalenedicarboxylic acid is preferable, and terephthalic acid is more preferable.

Only one type of dicarboxylic acid compound may be used, or two or more types may be used in combination. When terephthalic acid is used as the dicarboxylic acid compound, terephthalic acid may be used alone, or may be copolymerized with another aromatic dicarboxylic acid such as isophthalic acid or an aliphatic dicarboxylic acid.

-Diol compound-
Examples of diol compounds include aliphatic diol compounds, alicyclic diol compounds, and aromatic diol compounds, with aliphatic diol compounds being preferred.

Examples of aliphatic diol compounds include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,2-butanediol, 1,3-butanediol, and neo Pentyl glycol may be mentioned, with ethylene glycol being preferred.
Alicyclic diol compounds include, for example, cyclohexanedimethanol, spiroglycol, and isosorbide.
Examples of aromatic diol compounds include bisphenol A, 1,3-benzenedimethanol, 1,4-benzenedimethanol, and 9,9′-bis(4-hydroxyphenyl)fluorene.
Only one kind of diol compound may be used, or two or more kinds thereof may be used in combination.

-Terminal blocking agent-
In the production of the polyester resin, if necessary, a terminal blocker may be used. By using the terminal blocking agent, a structure derived from the terminal blocking agent is introduced to the terminal of the polyester resin.
The terminal blocking agent is not limited, and known terminal blocking agents can be used. Examples of terminal blocking agents include oxazoline-based compounds, carbodiimide-based compounds, and epoxy-based compounds.
As the end blocking agent, the content described in [0055] to [0064] of JP-A-2014-189002 can also be referred to, and the content of the above publication is incorporated herein.

-Manufacturing conditions-
The reaction temperature is not limited, and may be appropriately set according to the raw materials. The reaction temperature is preferably 260-300°C, more preferably 275-285°C.
The pressure is not limited, and may be appropriately set according to the raw material. The pressure is preferably 1.33×10 ⁻³ to 1.33×10 ⁻⁵ MPa, more preferably 6.67×10 ⁻⁴ to 6.67×10 ⁻⁵ MPa.

As a method for synthesizing the polyester resin, the method described in [0033] to [0070] of Japanese Patent No. 5575671 can also be used, and the contents of the above publication are incorporated herein.

Preferably, the polyester substrate is a biaxially oriented polyester substrate.
"Biaxial orientation" means the property of having molecular orientation in two axial directions. The molecular orientation is measured using a microwave transmission type molecular orientation meter (for example, MOA-6004, manufactured by Oji Scientific Instruments Co., Ltd.). The angle formed by the two axial directions is preferably within the range of 90°±5°, more preferably within the range of 90°±3°, and still more preferably within the range of 90°±1°.

The content of the polyester resin in the polyester base is preferably 85% by mass or more, more preferably 90% by mass or more, still more preferably 95% by mass or more, and 98% by mass, based on the total mass of the polymer in the polyester base. % or more is particularly preferred.
The upper limit of the content of the polyester resin is not limited, and can be appropriately set within a range of 100% by mass or less with respect to the total mass of the polymer in the polyester base material.

When the polyester base material contains polyethylene terephthalate, the content of polyethylene terephthalate is preferably 90 to 100% by mass, more preferably 95 to 100% by mass, based on the total mass of the polyester resin in the polyester base material. 100% by mass is more preferred, and 100% by mass is particularly preferred.

The polyester base material may contain components other than the polyester resin (eg, catalyst, unreacted raw material components, particles, water, etc.).

The thickness of the polyester base material is preferably 100 μm or less, more preferably 50 μm or less, and even more preferably 40 μm or less, in terms of controlling the peelability. Although the lower limit of the thickness is not particularly limited, it is preferably 3 μm or more, more preferably 10 μm or more, and even more preferably 20 μm or more in terms of improving strength and workability.
The thickness of the polyester base material is measured according to the method for measuring the thickness of the polyester film, which will be described later.

Although the film may further comprise a layer other than the above resin layer and polyester base material, it preferably has a layer structure consisting of a resin layer and a polyester base material.

[Physical properties, etc.]
Next, the physical properties and the like of this film will be described.

<Physical properties of the second main surface>
(ratio A)
For this film, a region with an area of 10000 μm ² on the second main surface is observed using a scanning electron microscope, and when a projection with the longest major axis is selected in the above region, the selected satisfies the requirement A that the ratio A of the height of the selected protrusions measured by non-contact surface profilometry using an optical interferometer to the major diameter of the selected protrusions is 0.7 or less.
By producing a release film using this film that satisfies Requirement A, it is possible to suppress the occurrence of uneven defects in a ceramic green sheet produced using the obtained release film.

The ratio A is 0.7 or less, preferably 0.6 or less. Within the above range, the occurrence of uneven defects in the ceramic green sheet can be further suppressed.
Although the lower limit is not particularly limited, it is preferably 0.01 or more, more preferably 0.03 or more, and still more preferably 0.05 or more in terms of excellent high-speed transportability and suppression of unevenness in protrusion height.

The ratio A of the second main surface of the polyester film is adjusted by, for example, the type and average particle size of the particles used in the production of the resin layer, the thickness of the resin layer, and the heat treatment after the resin layer forming step described later. can. A method for producing a polyester film that allows the above adjustments to be made more easily will be described later in detail.
The ratio A of the second main surface of the polyester film is measured according to the method described in the Examples section below.
The projections on the second main surface do not include dirt, foreign matter, and dirt adhered from the line or equipment during the manufacturing process of the polyester base material.

(Protrusion height on the second principal surface, protrusion length)
The resin layer of the present film functions as a conveying surface in the present film or in a release film obtained by forming a release layer on the first main surface. The height of the projections on the second main surface of the present film is preferably 0.1 μm or more, more preferably 0.2 μm or more, still more preferably 0.25 μm or more, and particularly 0.3 μm or more, from the viewpoint of excellent high-speed transportability. preferable.
On the other hand, if the protrusions formed on the second main surface are too large, the substance forming the protrusions tends to fall off during high-speed transportation. Further, when the release film is stored in a roll, etc., a transfer trace may be formed on the release layer. From these points, the height of the protrusions on the second main surface is preferably 5 μm or less, more preferably 4.0 μm or less, and even more preferably 3.5 μm or less.
That is, the height of the projections on the second main surface is preferably within the range defined by the above lower limit and upper limit in terms of the advantages of the present invention and high-speed transportability. .
In this specification, the term “protrusion height on the second main surface” refers to a region with an area of 10000 μm ² on the second main surface observed using a scanning electron microscope, and the projection having the longest major axis in the above region. In contrast, it means the protrusion height obtained by non-contact profilometry using an optical interferometer.

In addition, in terms of excellent high-speed transportability and excellent suppression of uneven defects, the height of the protrusions on the second main surface is 0.3 to 5.0 μm, and the thickness of the resin layer is 20 to 500 nm ( more preferably 20 to 200 nm), and the height of the protrusions on the second main surface is preferably larger than the thickness of the resin layer.

Moreover, the long diameter of the projections on the second main surface of the present film is preferably 1 to 20 μm.
The projection height and projection length on the second main surface can be adjusted according to the method for adjusting the ratio A described above.
Also, the projection height and the projection length on the second main surface are measured according to the method described in the Examples section below.

(Average Surface Roughness Sa of Second Principal Surface)
The surface average roughness Sa of the second main surface is preferably 1 to 15 nm, more preferably 1 to 10 nm, and even more preferably 1 to 8 nm, in that uneven defects on the release surface of the release film can be further suppressed.
The surface average roughness Sa of the second main surface is, for example, the average particle diameter and content of particles used for producing the resin layer, the thickness of the resin layer, and the non-polyester resin and additives ( It can be adjusted by selecting the type of surfactant, etc.). When the resin layer is formed by in-line coating, the above adjustments can be made more easily.

The surface average roughness Sa of the second main surface is the surface of the polyester film on the side of the specific coating layer using an optical interferometer (for example, "Vertscan 3300G Lite" manufactured by Hitachi High-Tech Co., Ltd.). It is obtained by measuring under the same conditions as the projection height measurement conditions, and then analyzing it with the built-in data analysis software. In the measurement of the surface average roughness Sa, measurements are performed five times at different measurement positions, and the average value of the obtained measurement values is used as the measurement value of the surface average roughness Sa.

(Surface free energy of second main surface)
The surface free energy of the second main surface of the present film is 25 to 65 mJ/m ² in terms of improving windability during high-speed transportation and excellent effect of suppressing uneven defects during long-term storage. Preferably, 25 to 45 mJ/m ² is more preferable, and 35 to 45 mJ/m ² is even more preferable. When the surface free energy of the second principal surface is within the above range, it is possible to prevent impurities such as oligomers generated from the polyester base material from passing through the resin layer and depositing on the surface of the second principal surface. As a result, when the release film produced using the present film is wound into a roll and stored for a long period of time, the oligomer-derived particles generated on the conveying surface (second main surface) adhere to the release surface of the release film. Therefore, it is possible to suppress the occurrence of irregularities in the ceramic green sheet formed on the release surface.
The surface free energy of the second principal surface can be adjusted, for example, by selecting the non-polyester resin and additives contained in the resin layer.
The surface free energy of the second main surface of this film is obtained according to the method described in the Examples section below.

<Physical properties of the first main surface>
(Maximum protrusion height Sp of first main surface, surface average roughness Sa)
From the viewpoint of smoothing the release layer, the first main surface is preferably as smooth as possible. Specifically, the maximum protrusion height Sp of the first main surface is preferably 1 to 60 nm, more preferably 1 to 50 nm, and even more preferably 1 to 30 nm.
The surface average roughness Sa of the first main surface is preferably 0 to 10 nm, more preferably 0 to 5 nm, even more preferably 0 to 2 nm.

The maximum protrusion height Sp and the surface average roughness Sa of the first main surface are the type and addition of the polyester that constitutes the polyester base material so that the polyester base material is substantially free of particles and the film is formed smoothly. It can be adjusted by a technique such as selecting the type of agent.
The maximum protrusion height Sp and the surface average roughness Sa of the first main surface of the present film are measured using an optical interferometer (for example, "Vertscan 3300G Lite" manufactured by Hitachi High-Tech Co., Ltd.). is obtained by measuring under the same conditions as the measurement conditions for the protrusion height when obtaining , and then analyzing it with the built-in data analysis software. In the measurement of the maximum projection height Sp and the surface average roughness Sa, measurements are performed five times at different measurement positions on the first main surface, and the average value of the obtained measurement values is used as each measurement value.

(Surface free energy of first main surface)
The surface free energy of the first main surface of the film is preferably 25 to 65 mJ/m ² , more preferably 30 to 45 mJ/m ² from the viewpoint of antistatic property when winding the film.
The surface free energy of the first main surface can be adjusted by selecting the type of resin forming the polyester base material, additives, and the like.

The surface free energy of the first main surface of the film can be measured according to the method for measuring the surface free energy of the second main surface described above.

<Thickness>
The thickness of the present film is preferably 100 μm or less, more preferably 50 μm or less, and even more preferably 40 μm or less, from the viewpoint of better peelability. Although the lower limit of the thickness is not particularly limited, it is preferably 3 μm or more, more preferably 5 μm or more, and still more preferably 10 μm or more from the viewpoint of excellent handleability.
The thickness of this film is the arithmetic average value of the thicknesses measured at five points with a continuous stylus film thickness gauge.

[Method for producing polyester film]
Examples of a method for producing a polyester film include a method comprising a biaxial stretching step of biaxially stretching an unstretched polyester base material and a step of forming a resin layer having projections.

The biaxial stretching may be simultaneous biaxial stretching in which longitudinal stretching and lateral stretching are performed simultaneously, or sequential biaxial stretching in which longitudinal stretching and lateral stretching are performed in multiple stages of two or more stages. The order of sequential biaxial stretching is, for example, the order of longitudinal stretching and transverse stretching, the order of longitudinal stretching, transverse stretching and longitudinal stretching, the order of longitudinal stretching, longitudinal stretching and transverse stretching, and the order of transverse stretching and longitudinal stretching. and the order of longitudinal stretching and transverse stretching is preferred.

[First embodiment]
As a first embodiment of the method for producing this film,
Step 1 (hereinafter also referred to as “longitudinal stretching step”) for producing a uniaxially oriented film by stretching an unstretched polyester film having a polyester base material in the longitudinal direction;
Step 2 of forming a resin layer on the surface of the uniaxially oriented film using a composition containing organic particles (hereinafter also referred to as "resin layer forming step");
A process for producing a polyester film comprising a step 3 of stretching in the width direction while heating the uniaxially oriented film having the resin layer (hereinafter also referred to as a "transverse stretching step"),
Of the temperature of the endothermic peak and the temperature of the baseline shift that appear in the curve (DSC curve) showing the change in the amount of heat obtained by measuring the organic particles with a differential scanning calorimeter, the lowest temperature is X, and step 3 (transverse stretching step), wherein the temperature X is lower than the temperature Y, where Y is the surface temperature of the uniaxially oriented film.

After forming a resin layer on a uniaxially oriented film using a composition containing organic particles having a temperature X measured by the above method (hereinafter also referred to as "composition A1"), in the lateral stretching step, By heating the uniaxially oriented film having the resin layer at a temperature Y higher than the temperature X, the organic particles existing on the surface of the resin layer are softened, and the organic particles easily follow the deformation of the resin layer due to lateral stretching. Become. As a result, protrusions having a low height-to-major axis ratio A are likely to be formed on the surface of the resin layer that serves as the second main surface of the polyester film.
As already explained, a release film obtained by using a polyester film having projections with such a low ratio A on the second main surface is used in the production of ceramic green sheets to eliminate uneven defects in the ceramic green sheets. Occurrence can be further suppressed.

The manufacturing method according to this embodiment will be described in detail below.

<Longitudinal stretching step (step 1)>
As the unstretched polyester film having a polyester substrate to be subjected to the longitudinal stretching step (step 1), an unstretched polyester substrate is preferable.
The polyester base material used in the longitudinal stretching step is as already described in the above item <Polyester base material>, including preferred embodiments. An unstretched polyester base material can be produced, for example, by the extrusion molding process of the second embodiment described later.

The longitudinal stretching can be performed, for example, by applying tension between two or more pairs of stretching rolls installed in the transport direction while transporting the unstretched polyester base material in the longitudinal direction.
The draw ratio in the longitudinal drawing step is appropriately set depending on the application, but is preferably 2.0 to 5.0 times, more preferably 2.5 to 4.0 times, and still more preferably 2.8 to 4.0 times. .
The stretching speed in the longitudinal stretching step is preferably 800 to 1500%/second, more preferably 1000 to 1400%/second, even more preferably 1200 to 1400%/second. Here, the "stretching speed" is a value obtained by dividing the length Δd of the polyester substrate in the transport direction stretched per second in the longitudinal stretching step by the length d0 of the polyester substrate in the transport direction before stretching. , is the value expressed as a percentage.
In the longitudinal stretching step, it is preferable to heat the unstretched polyester base material. This is because longitudinal stretching is facilitated by heating. The heating temperature in the longitudinal stretching step is preferably 70 to 120°C, more preferably 80 to 110°C, even more preferably 85 to 100°C.
Here, the "temperature" in each step of the manufacturing method according to this embodiment means the surface temperature of the film-like member measured using a non-contact thermometer (for example, a radiation thermometer). The surface temperature of the film-like member is obtained by measuring the temperature of the central portion in the width direction of the film-like member five times and calculating the average value of the obtained measured values.

<Resin Layer Forming Step (Step 2)>
In the resin layer forming step (step 2), a resin layer is formed on the surface of the uniaxially oriented film obtained in the longitudinal stretching step using the composition A1 containing organic particles.
The resin layer formed in the resin layer forming step has the same meaning as the layer described in detail in the above <Resin layer> except that it is specified as a resin layer including protrusions formed of organic particles.
Examples of the resin layer forming step include a method of forming a coating film on the surface of a longitudinally stretched uniaxially oriented film using the composition A1, and drying the film as necessary.

First, a method for forming a resin layer using composition A1 will be described.
Composition A1 can be prepared, for example, by mixing organic particles, non-polyester resin, solvent, and optional additives.

The average particle size of the organic particles contained in the composition A1 is not particularly limited, but is preferably 1 nm or more and 3 μm or less, more preferably 10 nm or more and 2 μm or less, in terms of better transportability and the ability to suppress transfer marks.

The organic particles contained in the composition A1 may be used singly, or two or more kinds of organic particles may be used.
When the composition A1 contains two or more types of organic particles having different particle sizes, the resin layer preferably contains at least one type of organic particles having an average particle size within the above range, and two or more types having different particle sizes. It is more preferable that all of the organic particles in (1) are organic particles having an average particle size within the above range.

The shape of the organic particles is not particularly limited, and examples thereof include rice grain-like, spherical, cubic, spindle-like, scale-like, aggregated, and irregular shapes. Aggregate means a state in which primary particles are aggregated.

The content of the organic particles in the composition A1 is 0.1 to 30 mass with respect to the total mass of the components (solid content) other than the solvent in the composition A1 from the viewpoint of transportability and coatability of the release layer. %, more preferably 1 to 25% by mass, even more preferably 1 to 20% by mass.

Examples of solvents include water and ethanol.
Composition A1 may contain a single solvent, or may contain two or more solvents.
The solvent content is preferably 80 to 99.5% by mass, more preferably 90 to 99.0% by mass, based on the total mass of composition A1.
That is, in composition A1, the total solid content is preferably 0.5 to 20% by mass, more preferably 1 to 10% by mass, relative to the total mass of composition A1.

The organic particles, the material composing the organic particles, the non-polyester resin, and the additive contained in the composition A1 are as described in detail in the section <Resin Layer> above, including their preferred embodiments.
For each component other than the solvent and the organic particles in composition A1, the content of each component with respect to the total mass of the solid content of composition A1 is the same as the preferred content of each component with respect to the total mass of the resin layer. Thus, it is preferable to adjust the content of each component in the coating liquid.

Composition A1 may contain a cross-linking agent.
The cross-linking agent is not particularly limited, and known ones can be used.
Examples of cross-linking agents include melamine-based compounds, oxazoline-based compounds, epoxy-based compounds, isocyanate-based compounds, and carbodiimide-based compounds, with oxazoline-based compounds and carbodiimide-based compounds being preferred. Examples of commercially available products include Carbodilite V-02-L2 (manufactured by Nisshinbo Co., Ltd.) and Epocross K-2020E (manufactured by Nippon Shokubai Co., Ltd.). For details of the epoxy-based compound, the isocyanate-based compound, and the melamine-based compound, reference can be made to [0081] to [0083] of JP-A-2015-163457. The cross-linking agents described in [0082] to [0084] of International Publication No. 2017/169844 can also be preferably used. As for the carbodiimide compound, the descriptions in [0038] to [0040] of JP-A-2017-087421 can be referred to.
For oxazoline-based compounds, carbodiimide-based compounds, and isocyanate-based compounds, cross-linking agents described in [0074] to [0075] of WO 2018/034294 can also be preferably used.
The content of the cross-linking agent is preferably 0 to 50% by mass based on the total mass of the solid content of composition A1.

The method of applying composition A1 is not particularly limited, and known methods can be used. Examples of coating methods include spray coating, slit coating, roll coating, blade coating, spin coating, bar coating and dip coating.

In the resin layer forming step, it is preferable to apply an in-line coating method in which the composition A1 is applied to one surface of the uniaxially oriented film while the uniaxially oriented film is conveyed. By applying the in-line coating method, the heating time of the polyester base material in the manufacturing process is shortened and the heat history is not applied, so that the generation of distortion in the release film can be suppressed.
Moreover, in this embodiment, after the longitudinal stretching process, the resin layer forming process is carried out, and then the transverse stretching process is carried out. Thereby, the adhesion between the polyester substrate and the resin layer can be improved by simultaneously laterally stretching the uniaxially oriented polyester substrate and the resin layer.

<Lateral stretching step (step 3)>
In the present embodiment, a uniaxially oriented film having a resin layer (in the present embodiment, also simply referred to as "uniaxially oriented film") is stretched in the width direction (hereinafter also referred to as "transverse stretching") to biaxially stretch the film. The uniaxially oriented film is heated at a specific temperature Y when performing the lateral stretching step (step 3) for forming the oriented polyester substrate.
The heating temperature Y at that time is not particularly limited as long as it is higher than the temperature X of the organic particles contained in the resin layer. More preferred.
Moreover, it is preferable that the uniaxially oriented film is continuously heated at the temperature Y while being laterally stretched in the lateral stretching step.

In the lateral stretching step, it is preferable to preheat the uniaxially oriented film before lateral stretching. By raising the temperature of the polyester base material by preheating, the uniaxially oriented film can be easily laterally stretched. The preheating temperature is preferably 80 to 120°C, more preferably 90 to 110°C.
The draw ratio in the width direction of the uniaxially oriented film in the transverse stretching step (lateral draw ratio) is not particularly limited, but is preferably larger than the draw ratio in the longitudinal stretching step. The draw ratio in the transverse drawing step is preferably 3.0 to 6.0 times, more preferably 3.5 to 5.0 times, even more preferably 3.5 to 4.5 times.
When the lateral stretching step is carried out in the stretching section of the stretching machine, the lateral stretching ratio is the ratio of the polyester substrate width L1 at the time of unloading from the stretching unit to the polyester substrate width L0 at the time of loading into the stretching unit (L1/L0). requested from.
The stretching speed in the lateral stretching step is preferably 8 to 45%/second, more preferably 10 to 30%/second, even more preferably 15 to 20%/second.

The manufacturing method according to the present embodiment may have other processes in addition to the longitudinal stretching process, the resin layer forming process, and the lateral stretching process.
The production method according to the present embodiment includes, for example, an extrusion molding step of extruding a molten resin containing a raw material polyester resin into a film to form an unstretched polyester base material, and heating a biaxially oriented polyester base material. A heat setting step of fixing, a heat relaxation step of heating the polyester base material heat-set by the heat setting step at a temperature lower than that of the heat setting step for thermal relaxation, and a heat relaxation step of cooling the polyester base material heat-relaxed. It may have at least one step selected from the group consisting of a cooling step and an expanding step of expanding the heat-relaxed polyester base material in the width direction in the cooling step.
Each step of the extrusion molding step, the heat setting step, the heat relaxation step, the cooling step, and the expansion step will be described in detail in a second embodiment described later.

The production method according to the present embodiment may have a winding step of obtaining a roll-shaped biaxially oriented polyester substrate by winding the biaxially oriented polyester substrate obtained through the above steps. .
The transport speed of the polyester base material in each step other than the longitudinal stretching step of the production method according to the present embodiment is not particularly limited, but in terms of productivity and quality, it is preferably 50 to 200 m / min, and 80 to 150 m / min. is more preferred.

[Second embodiment]
As a second embodiment of the method for producing the present film, an extrusion molding step of extruding a molten resin containing a raw material polyester resin into a film to form an unstretched polyester base material, and stretching the unstretched polyester base material in the conveying direction. a biaxial stretching step consisting of a longitudinal stretching step of forming a uniaxially oriented polyester base material by stretching, and a lateral stretching step of stretching the uniaxially oriented polyester base material in the width direction to form a biaxially oriented polyester base material; A heat setting step of heating and heat setting the axially oriented polyester base material, a heat relaxation step of heating and thermally relaxing the polyester base material heat set by the heat setting step at a temperature lower than that of the heat setting step, and heat relaxation. A cooling step of cooling the polyester base material thermally relaxed by the step, an expansion step of expanding the thermally relaxed polyester base material in the width direction in the cooling step, and an in-line using a resin layer-forming composition containing particles and a resin layer forming step of providing a resin layer on one surface of the polyester substrate by a coating method.

<Extrusion molding process>
The extrusion molding step is a step of forming an unstretched polyester base material by extruding a molten resin containing a polyester resin as a raw material into a film by an extrusion molding method. The raw material polyester resin is synonymous with the polyester resin described in the item (polyester resin) above.

The extrusion molding method is, for example, a method of molding a raw material resin into a desired shape by extruding a melt of the raw material resin using an extruder.
The melt extruded from the extrusion die is cooled to form a film. For example, the melt can be formed into a film by contacting the melt with a casting roll and cooling and solidifying the melt on the casting roll. In cooling the melt, it is preferable to blow air (preferably cool air) to the melt.

<Biaxial stretching process>
The biaxial stretching step includes a longitudinal stretching step of longitudinally stretching an unstretched polyester substrate to form a uniaxially oriented polyester substrate, and a lateral stretching step of a uniaxially oriented polyester substrate to form a biaxially oriented polyester substrate. It has a lateral stretching process.
In the longitudinal stretching step and the lateral stretching step in the production method according to the present embodiment, the uniaxially oriented polyester base material stretched in the lateral stretching step is not limited to a uniaxially oriented film having a resin layer, and the lateral stretching Except that the process is not limited to the aspect of heating at a specific temperature Y while laterally stretching, it is the same as the longitudinal stretching step and the lateral stretching step of the first embodiment, and is the same as each step in the first embodiment. can be implemented in

<Heat setting process>
In the manufacturing method according to the present embodiment, it is preferable to perform a heat setting step as the heat treatment for the polyester base material laterally stretched in the lateral stretching step.
In the heat setting step, the biaxially oriented polyester substrate obtained by the lateral stretching step can be heated and heat set. By crystallizing the polyester resin by heat setting, shrinkage of the polyester base material can be suppressed.
The surface temperature (heat setting temperature) of the polyester base material in the heat setting step is not particularly limited, but is preferably less than 240°C, more preferably 235°C or less, and even more preferably 230°C or less. Although the lower limit is not particularly limited, it is preferably 190°C or higher, more preferably 200°C or higher, and even more preferably 210°C or higher.
The heating time in the heat setting step is preferably 5 to 50 seconds, more preferably 5 to 30 seconds, even more preferably 5 to 10 seconds.

<Thermal relaxation process>
In the thermal relaxation step, it is preferable to thermally relax the polyester base material heat-set in the heat-setting step by heating at a temperature lower than that in the heat-setting step. Thermal relaxation can relieve the residual strain of the polyester substrate.
The surface temperature (thermal relaxation temperature) of the polyester base material in the thermal relaxation step is preferably 5°C or more lower than the heat setting temperature, more preferably 15°C or more lower, still more preferably 25°C or more lower, and 30°C. Lower temperatures are particularly preferred. That is, the thermal relaxation temperature is preferably 235°C or lower, more preferably 225°C or lower, still more preferably 210°C or lower, and particularly preferably 200°C or lower.
The lower limit of the thermal relaxation temperature is preferably 100°C or higher, more preferably 110°C or higher, and even more preferably 120°C or higher.

<Cooling process>
The production method according to the present embodiment preferably has a cooling step of cooling the thermally relaxed polyester base material.
The cooling rate of the polyester base material in the cooling step is not particularly limited, but it is more than 2000 ° C./min and 4000 ° C./min in that the thickness unevenness of the release layer laminated on the present film is reduced and the coatability of the release layer is more excellent. It is preferably less than 2000 to 3500°C/min, more preferably more than 2200°C/min to less than 3000°C/min, and particularly preferably 2300 to 2800°C/min. In addition, in order to reduce heat shrinkage and impart dimensional stability, the cooling rate of the polyester film in the cooling step is preferably more than 500 ° C./min and less than 4000 ° C./min, and more preferably 700 to 3000 ° C./min. Preferably, 1000-2500° C./min is particularly preferred.

<Expansion process>
The cooling step preferably includes a step of expanding the thermally relaxed polyester base material in the width direction.
The expansion rate of the polyester base material in the width direction by the expansion process, that is, the ratio of the polyester base width at the end of the cooling process to the polyester base width before the start of the cooling process is preferably 0% or more, and 0.001%. 0.01% or more is more preferable.
Although the upper limit of the expansion rate is not particularly limited, it is preferably 1.3% or less, more preferably 1.2% or less, and even more preferably 1.0% or less.

<Resin layer forming step>
The production method according to the present embodiment preferably includes a resin layer forming step of in-line coating with a resin layer forming composition containing particles (hereinafter also referred to as “composition A”).
The resin layer forming step in the present embodiment includes using the composition A instead of the composition A1, applying an in-line coating method for applying the composition A to one surface of the polyester substrate, and applying the composition. Except that the object to be coated is not limited to a uniaxially oriented film, the resin layer forming step is the same as the resin layer forming step of the first embodiment, and can be carried out in the same manner as the resin layer forming step of the first embodiment.
As the composition A used in the resin layer forming step of the present embodiment, the composition A1 of the first embodiment is preferred, including more preferred embodiments.

In the resin layer forming step of the present embodiment, the polyester substrate to which the composition A is applied may be an unstretched polyester substrate or a uniaxially oriented polyester substrate. An oriented polyester substrate is preferred. That is, it is preferable that the resin layer forming step is a coating step performed between the longitudinal stretching step and the lateral stretching step. This is because the adhesion between the polyester base material and the resin layer can be improved by simultaneously laterally stretching the uniaxially oriented polyester base material and the resin layer.

The manufacturing method according to this embodiment may have a winding step as in the first embodiment.
In addition, although the transport speed of the polyester base material in each step other than the longitudinal stretching step of the production method according to the present embodiment is not particularly limited, the transverse stretching step, heat setting step, heat relaxation step, cooling step and expansion step are performed. In this case, 50 to 200 m/min is preferable, and 80 to 150 m/min is more preferable in terms of productivity and quality.

The method for producing this film is not particularly limited as long as it is a method for producing a polyester film that has a resin layer and a polyester base material, has a first main surface and a second main surface, and satisfies the requirement A. , manufacturing methods other than those of the above-described first and second embodiments may be used.

For example, by co-extruding a molten resin containing a raw material polyester resin for forming an unstretched polyester base material and a particle-containing molten resin containing particles for forming a resin layer and a non-polyester resin, an unstretched polyester The present film may be produced by forming a laminate in which a substrate and a resin layer are laminated, and then biaxially stretching the laminate.

Regarding the production method of this film, the contents described in [0113] to [0169] of International Publication No. 2020/241692 can be referred to, and the contents thereof are incorporated herein.
In addition, in the method for producing the present film specifically described above, a combination of two or more preferred aspects is a more preferred aspect.

[Release film]
The film can be used to make release films. More specifically, by providing a release layer on the first main surface of the film, a release film having the film and the release layer disposed on the first main surface of the film can be produced.

The release layer contains at least a resin as a release agent. Resins contained in the release layer are not particularly limited, and examples thereof include silicone resins, fluororesins, alkyd resins, acrylic resins, various waxes, and aliphatic olefins. When the release film is a release film for producing a ceramic green sheet, which will be described later, a silicone resin is preferable from the viewpoint of the release property of the ceramic green sheet.

A silicone resin means a resin having a silicone structure in its molecule. Examples of silicone resins include curable silicone resins, silicone graft resins, and modified silicone resins such as alkyl-modified silicone resins, and reactive curable silicone resins are preferred.
Examples of reactive curable silicone resins include addition reaction silicone resins, condensation reaction silicone resins, and ultraviolet or electron beam curable silicone resins. Among them, an addition reaction type silicone resin having low-temperature curability or an ultraviolet or electron beam curing type silicone resin is preferable because the release layer can be formed at a low temperature.

Examples of addition reaction silicone resins include resins obtained by reacting and curing polydimethylsiloxane having a terminal or side chain introduced with a vinyl group and hydrogen siloxane using a platinum catalyst.
As the condensation reaction silicone resin, for example, a three-dimensional polydimethylsiloxane having terminal OH groups and a polydimethylsiloxane having terminal H groups are subjected to a condensation reaction using an organic tin catalyst. Examples thereof include resins having a crosslinked structure.
Examples of UV-curing silicone resins include those that use the same radical reaction as silicone rubber cross-linking, those that introduce photo-curing by introducing unsaturated groups, those that generate strong acids by decomposing onium salts with ultraviolet rays or electron beams, and epoxy resins. Those that crosslink by cleaving the groups and those that crosslink by the addition reaction of thiol to vinyl siloxane are included. More specific examples include acrylate-modified polydimethylsiloxane and glycidoxy-modified polydimethylsiloxane.

The release layer may contain additives in addition to the above resins. As additives, additives such as a light release additive and a heavy release additive for adjusting the release force, an adhesion improver, a curing agent (crosslinking agent), and an antistatic agent may be added.
The resin contained in the release layer may be used singly or in combination of two or more.
The content of the resin in the release layer is preferably 50 to 99% by mass, more preferably 60 to 98% by mass, based on the total mass of the release layer. The rest of the release layer other than the resin may be at least one of the above additives and residues such as solvents and catalysts contained in the release layer forming coating liquid used to form the release layer.

The thickness of the release layer may be set according to the purpose of use, and is not particularly limited. 0.05 to 1.0 μm is more preferred.

<Surface free energy of peeled surface>
In terms of antistatic properties when winding the release film, the surface free energy of the surface of the release layer opposite to the polyester film side (also referred to as the release surface) is preferably 30 mJ/ ^m2 or less, and is 1 to 30 mJ/m. ² is more preferred, and 10 to 30 mJ/m ² is even more preferred.
The surface free energy of the release surface of the release layer can be adjusted by the type of resin forming the release layer and additives.

<Maximum projection height Sp of peeled surface, surface average roughness Sa>
The release surface is preferably as smooth as possible in order to smooth the functional layer such as a ceramic green sheet formed on the release layer. Specifically, the maximum projection height Sp of the peeled surface is preferably 1 to 60 nm, more preferably 1 to 40 nm.
The surface average roughness Sa of the peeled surface is preferably 0 to 10 nm, more preferably 0 to 5 nm.
The maximum protrusion height Sp and surface average roughness Sa of the release surface are determined, for example, by not putting particles in the release layer when providing the release layer, and by selecting the resin and additives that form the release layer. Adjustable.
The maximum protrusion height Sp and surface average roughness Sa of the release surface can be measured according to the above-described method for measuring the maximum protrusion height Sp and surface average roughness Sa of the first main surface of the present film.

The method of providing the release layer on the first main surface of the film is not particularly limited, but a coating solution for forming a release layer in which a release agent is dissolved or dispersed in a solvent is applied to the first main surface of the film, A method of removing the solvent by drying and, if necessary, heating or irradiating with light to form a cured product can be mentioned.
The release layer is preferably a cured product cured by light (eg, ultraviolet rays) or heat.

The coating method of the release layer forming coating liquid is not particularly limited, and a known method can be used. Examples of coating methods include spray coating, slit coating, roll coating, blade coating, spin coating, bar coating and dip coating.
The heating temperature for forming the release layer is preferably 180° C. or lower, more preferably 150° C. or lower, and even more preferably 120° C. or lower. The lower limit is not particularly limited, and may be 60°C or higher.

The release layer-forming coating liquid contains the above resin and solvent, and if necessary, may contain at least one of the above additives and the above catalyst used for curing the resin. The release layer-forming coating liquid can be prepared by mixing these components.
Examples of solvents include water and organic solvents such as toluene, methyl ethyl ketone, ethanol, ethylene glycol monoethyl ether, ethylene glycol dimethyl ether, propylene glycol monomethyl ether and propylene glycol monoethyl ether.

The release layer-forming coating liquid may contain a single solvent, or may contain two or more solvents.
The content of the solvent is preferably 80 to 99.5% by mass, more preferably 90 to 99% by mass, based on the total mass of the coating liquid for forming a peeling layer.
That is, in the release layer-forming coating liquid, the total content of components (solid content) other than the solvent is preferably 0.5 to 20% by mass, preferably 1 to 10%, based on the total mass of the release layer-forming coating liquid. % by mass is more preferred.

In order to improve the adhesion between the present film and the release layer, the first main surface of the present film is subjected to pretreatment such as anchor coating, corona treatment, and plasma treatment before providing the release layer. good too.

[Use]
A release film having this film is preferably used as a release film (carrier film) for producing a ceramic green sheet. The ceramic green sheet produced using the above release film can be suitably used for production of ceramic capacitors for which multi-layered internal electrodes are required in accordance with miniaturization and increased capacity.
Moreover, the release film having the present film may be used as a protective film for dry film resist, a release film for process manufacturing such as a semiconductor process, and the like.

A method for producing a ceramic green sheet using the release film is not particularly limited, and a known method can be used. As a method for producing a ceramic green sheet, for example, a prepared ceramic slurry is applied to the surface of the release layer of the release film, and the solvent contained in the ceramic slurry is removed by drying.
The method of applying the ceramic slurry is not particularly limited. For example, a known method such as applying a ceramic slurry obtained by dispersing ceramic powder and a binder in a solvent by a reverse roll method and removing the solvent by heating and drying. method can be applied. The binder agent is not particularly limited, and examples thereof include polyvinyl butyral. Also, the solvent is not particularly limited, and examples thereof include ethanol and toluene.

The present disclosure will be described more specifically below with examples. Materials, usage amounts, proportions, processing details, and processing procedures shown in the following examples can be changed as appropriate without departing from the scope of the present disclosure. Accordingly, the scope of the present disclosure is not limited to the specific examples provided below. "Parts" and "%" are based on mass unless otherwise specified.

[Example 1]
<Extrusion molding process>
Polyethylene terephthalate pellets were produced using a titanium compound described in Japanese Patent No. 5575671 (citric acid chelate titanium complex, VERTEC AC-420, manufactured by Johnson Matthey) as a polymerization catalyst. The obtained pellets were dried to a moisture content of 50 ppm or less, put into a hopper of a twin-screw kneading extruder described in Japanese Patent No. 6049648, and then melted at 280°C and extruded. The melt was passed through a filter (pore size 3 μm) and then extruded from a die onto a cooling drum at 25° C. to obtain an unstretched film made of polyethylene terephthalate. The extruded melt (melt) was brought into close contact with the cooling drum by an electrostatic application method.
The polyethylene terephthalate constituting the unstretched film had a melting point (Tm) of 258°C and a glass transition temperature (Tg) of 80°C.

<Longitudinal stretching step (step 1)>
The unstretched film was subjected to a longitudinal stretching step by the following method.
A uniaxially oriented film was produced by passing the preheated unstretched film between two pairs of rolls having different circumferential speeds and stretching it in the machine direction (conveyance direction) under the following conditions.
(Longitudinal stretching conditions)
Preheating temperature: 75°C
Stretching temperature: 90°C
Stretch ratio: 3.4 times Stretching speed: 1300%/sec

<Resin Layer Forming Step (Step 2)>
On one side of a longitudinally stretched uniaxially oriented film (polyester base material), the following composition A-1 (resin layer forming composition) is applied with a bar coater, and the formed coating film is subjected to hot air at 100 ° C. and dried to form a resin layer on one side of the polyester substrate. In this step, the coating amount of composition A-1 was adjusted so that a resin layer having a thickness described later was formed in the finally produced biaxially oriented film.

(Composition A-1)
Composition A-1 was prepared by mixing each component shown below. The prepared composition A-1 was filtered using a filter with a pore size of 6 μm (F20, manufactured by Mahle Filter Systems Co., Ltd.), and membrane degassing (2x6 radial flow superphobic, Polypore Co., Ltd. ), the resulting composition A-1 was applied to the surface of the uniaxially oriented film.
・ Resin 1 (urethane resin, Takelac (registered trademark) W-605, manufactured by Mitsui Chemicals, Inc., an aqueous dispersion with a solid content concentration of 25% by mass): 157 parts by mass ・Anionic hydrocarbon surfactant ( Rapisol (registered trademark) A-90, di-2-ethylhexyl sodium sulfosuccinate, manufactured by NOF Corporation, solid content concentration 1% by mass diluted with water): 56 parts by mass Particles 1 (non-crosslinked styrene resin particles (styrene Polymer), Nipol (registered trademark) UFN1008, manufactured by Nippon Zeon Co., Ltd., average particle diameter 1.9 μm, aqueous dispersion adjusted to a solid content concentration of 10% by mass): 8 parts by mass, water: 779 parts by mass A scanning calorimeter (“DSC-60aPlus”, manufactured by Shimadzu Corporation) was used to measure the temperature X of the particles 1 according to the method described above, and the temperature X of the particles 1 was 100°C.

<Lateral stretching step (step 3)>
The film subjected to the longitudinal stretching step and the resin layer forming step was stretched in the width direction using a tenter under the following conditions to prepare a biaxially oriented film. The surface temperature (temperature Y) of the film in the lateral stretching step measured by the method described above was the same as the stretching temperature below.
(Lateral stretching conditions)
Preheating temperature: 100°C
Stretching temperature: 120°C
Stretch ratio: 4.2 times Stretching speed: 50%/sec

<Heat setting process>
The biaxially oriented film subjected to the lateral stretching step was subjected to a heat setting step of heat setting the film by heating under the following conditions using a tenter.
(Heat fixation conditions)
Heat setting temperature: 227°C
Heat fixation time: 6 seconds

<Thermal relaxation process>
Then, the heat-set film was subjected to a heat relaxation step for relaxing the tension of the film by heating under the following conditions. Also, in the heat relaxation step, the film width was reduced compared to that at the end of the heat setting step by narrowing the distance (tenter width) between the gripping members of the tenter that grips both ends of the film. The following thermal relaxation rate Lr was obtained from the film width L2 at the end of the thermal relaxation process with respect to the film width L1 at the start of the thermal relaxation process by the formula Lr=(L1−L2)/L1×100.
(Thermal relaxation conditions)
Thermal relaxation temperature: 190°C
Thermal relaxation rate Lr: 4%

<Cooling process and expansion process>
A cooling step was performed on the thermally relaxed film under the following conditions. Further, in the cooling process, an expansion process was carried out in which the width of the tenter was expanded to expand the width of the film compared to that at the end of the thermal relaxation process.
The following cooling rates were measured when the film surface temperature was measured when the film was carried into the cooling section and when the cooling section was carried out, with the cooling time ta being the time the film stayed in the cooling section after being carried into the cooling section of the stretching machine until it was taken out. It was obtained by dividing the temperature difference ΔT (°C) from the film surface temperature by the cooling time ta.
Further, the following expansion rate ΔL was obtained from the film width L3 at the end of the cooling process with respect to the film width L2 of the polyester film at the start of the cooling process, by the formula ΔL = (L3 - L2) / L2 × 100.
(Cooling condition)
Cooling rate: 2500°C/min (extended condition)
Expansion rate ΔL: 0.6%

<Winding process>
Using a trimming device, the film cooled in the cooling step was continuously cut along the conveying direction at positions 20 cm from both ends in the width direction of the film to trim both ends of the film. Then, the film was wound up with a tension of 40 kg/m after extrusion processing (knurling) was performed on a region from both ends of the film to 10 mm in the width direction.
A biaxially oriented film (polyester film) in which the polyester substrate and the resin layer were laminated was produced by the above method. The resulting biaxially oriented film had a thickness of 31 μm, a width of 1.5 m and a winding length of 7000 m.
In addition, the biaxially oriented film was cut using a microtome to prepare a sample having a cross section along the thickness direction of the biaxially oriented film, and the obtained sample was etched with Ar ions and vapor-deposited with Pt. After applying, the thickness of the resin layer in the cross section of the sample was measured by the above method using SEM (“S-4800” manufactured by Hitachi High-Tech Co., Ltd.), and the thickness of the resin layer was 60 nm. .

[Example 2]
Composition in Example 1, except that Resin 2 (urethane resin, Hydran (registered trademark) AP-40N, manufactured by DIC Corporation, an aqueous dispersion adjusted to a solid content concentration of 25% by mass) was used instead of Resin 1. Composition A-2 was prepared according to the preparation method of Product A-1.
A biaxially oriented film was produced according to the method described in Example 1, except that composition A-2 was used in place of composition A-1 in the resin layer forming step. The resulting biaxially oriented film had a thickness of 31 μm, a width of 1.5 m and a winding length of 7000 m. The thickness of the resin layer of the biaxially oriented film was 60 nm.

[Example 3]
Example 1 except that resin 3 (urethane resin, ADEKA BONDITTER (registered trademark) HUX-524, manufactured by ADEKA Corporation, an aqueous dispersion adjusted to a solid content concentration of 25% by mass) was used instead of resin 1. Composition A-3 was prepared according to the method for preparing composition A-1 in .
A biaxially oriented film was produced according to the method described in Example 1, except that composition A-3 was used in place of composition A-1 in the resin layer forming step. The resulting biaxially oriented film had a thickness of 31 μm, a width of 1.5 m and a winding length of 7000 m. Moreover, the thickness of the resin layer of the biaxially oriented film was 60 nm.

[Example 4]
Instead of Particle 1, Particle 2 (crosslinked urethane resin particles, Artpearl (registered trademark) C-1000T, manufactured by Negami Kogyo Co., Ltd., average particle diameter 3.0 μm, aqueous dispersion adjusted to a solid content concentration of 10% by mass). Composition A-4 was prepared according to the method for preparing composition A-2 in Example 2, except that it was used. As a result of measuring in the same manner as in Example 1, the temperature X of the particles 2 was -13°C.
A biaxially oriented film was produced according to the method described in Example 1, except that composition A-4 was used in place of composition A-1 in the resin layer forming step. The resulting biaxially oriented film had a thickness of 31 μm, a width of 1.5 m and a winding length of 7000 m. Moreover, the thickness of the resin layer of the biaxially oriented film was 60 nm.

[Comparative Example 1]
Particle 3 instead of particle 1 (non-crosslinked polymethyl methacrylate (PMMA) resin particles, Techpolymer (registered trademark) MB-4, manufactured by Sekisui Plastics Co., Ltd., average particle size 4.0 μm, solid content concentration 10 mass %) was prepared according to the method for preparing composition A-2 in Example 2, except that composition CA-1 was prepared. As a result of measuring in the same manner as in Example 1, the temperature X of the particles 3 was 102°C.
A biaxially oriented film was produced according to the method described in Example 1, except that composition CA-1 was used instead of composition A-1 in the resin layer forming step. The resulting biaxially oriented film had a thickness of 31 μm, a width of 1.5 m and a winding length of 7000 m. Moreover, the thickness of the resin layer of the biaxially oriented film was 60 nm.

[Comparative Example 2]
Resin 4 (copolymer obtained by polymerizing acrylic resin (methyl methacrylate, styrene, 2-ethylhexyl acrylate, 2-hydroxyethyl methacrylate and acrylic acid at a mass ratio of 59:8:26:5:2) instead of resin 1 ), solid content concentration 25% by mass) was used, and instead of particle 1, particle 4 (crosslinked acrylic resin particles, Eposter (registered trademark) MX200W, manufactured by Nippon Shokubai Co., Ltd., average particle diameter 0 Composition CA-2 was prepared according to the method for preparing composition A-1 in Example 2, except that an aqueous dispersion adjusted to .35 μm and a solid content concentration of 10% by mass was used. As a result of measuring in the same manner as in Example 1, the temperature X of the particles 4 was 105°C.
In accordance with the method described in Example 1, except that the composition CA-2 was used in place of the composition A-1 in the resin layer forming step, and the stretching temperature was set to 150 ° C. in the lateral stretching step, 2 An axially oriented film was produced. The surface temperature of the film in the transverse stretching step measured by the method described above was 150° C., the same as the stretching temperature. The resulting biaxially oriented film had a thickness of 31 μm, a width of 1.5 m and a winding length of 7000 m. Moreover, the thickness of the resin layer of the biaxially oriented film was 60 nm.

FIG. 1 shows an observation image (photograph) obtained by observing the second main surface of the biaxially oriented film (polyester film) produced in Example 3 by SEM, and FIG. An observed image (photograph) obtained by observing the second main surface of the biaxially oriented film obtained by observing with an SEM is shown.
As shown in FIG. 1, the projections present on the second main surface of the polyester film of the present invention have a shape extending along one direction within the surface. On the other hand, from FIG. 2, it can be observed that the projections present on the second main surface of the biaxially oriented film of Comparative Example 1 have clear outlines and nearly spherical shapes.

[Measurement of physical properties of biaxially oriented film]
The following physical properties were measured for the biaxially oriented films produced in each example and each comparative example.

<Ratio A, protrusion height, protrusion length>
After marking with a felt pen on the second main surface of the sample of the biaxially oriented film, platinum deposition was performed. With the sample tilted at 15° with respect to the horizontal plane, an SEM ("S4700", manufactured by Hitachi High-Tech Co., Ltd.) was used to image the vicinity of the mark on the second main surface at low magnification. Among the protrusions present in the observation area (measurement field) of 100 μm × 100 μm, the protrusion with the longest major axis was selected, and the image was taken at an increased magnification, and the major axis (maximum diameter in the in-plane direction) of the protrusion was measured. .
Then, using an optical interferometer (Vertscan 3300G Lite, manufactured by Hitachi High-Tech Co., Ltd.), the mark portion was measured under the following measurement conditions to confirm the distribution of protrusions. The distribution was collated with the observation result by SEM, and the protrusion observed by SEM was specified. After specifying the protrusion, the cross section of the protrusion was observed by two-dimensional analysis, and the height of the protrusion was measured.
From the measured long diameter and height of the projection, the ratio of the height of the projection to the long diameter of the specified projection was calculated.
(Measurement condition)
・Measurement mode: WAVE mode ・Objective lens: 50x ・Measurement area: 186 μm×155 μm

In 10 different observation areas on the second main surface of the sample, the length of the protrusion and the height corresponding to the protrusion were measured by the above method, and the ratio was calculated. The arithmetic average value of the ratios obtained for each observation area was adopted as the ratio A of the second main surface of the sample. Further, the length of the protrusions obtained for each observation area and the arithmetic mean value of the height corresponding to the protrusions were adopted as the height of the protrusions on the second main surface of the sample and the length of the protrusions, respectively.

<Surface free energy>
The surface free energy of the second main surface (the surface on which projections are present) of the biaxially oriented film was measured by the following method.
Using a contact angle meter (manufactured by Kyowa Interface Science Co., Ltd., DROPMASTER-501), droplets are dropped on the second main surface of the produced biaxially oriented film at 25 ° C., and the droplets are on the surface. The contact angle was measured 1 second after adhering. Using 2 μL of purified water, 1 μL of methylene iodide and 1 μL of ethylene glycol as droplets, the surface free energy (unit: mJ/m ² ) was calculated from the measured contact angles by the method of Kitazaki and Hata.
The "surface free energy" obtained by the above method is the sum of the polar component and the hydrogen bond component of the surface free energy.

[evaluation]
The biaxially oriented films produced in each example and each comparative example were evaluated as follows.

<Preparation of release film>
After leaving the film roll of the wound biaxially oriented film in an environment of temperature 25° C. and humidity 50% RH for 1 week, a release film was produced with reference to Example 1 of JP-A-2015-195291. .
Specifically, first, referring to Production Example 1 of JP-A-2015-195291, hexamethylene diisocyanate, dimethylorganopolysiloxane, and dipentaerythritol pentaacrylate (Aronix (registered trademark) M-400, Toa Gosei Co., Ltd.) to synthesize a curable silicone compound (A1). Next, 100 parts by mass of a curable silicone compound (A1) and 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl] as a photopolymerization initiator (B1). -Phenyl}-2-methyl-propan-1-one (manufactured by IGM Resins B.V., product name "Omnirad 127") and 5 parts by mass, in a mixed solvent of isopropyl alcohol and methyl ethyl ketone (mass ratio 3: 1) to obtain a release layer-forming coating liquid.
The obtained coating solution for forming a release layer was peeled off from the first main surface (surface on the side of the polyester substrate) of the above-mentioned biaxially oriented film after being left for one week so that the thickness after curing was 1 μm. A layer was applied and dried at 80° C. for 1 minute. Thereafter, ultraviolet rays were irradiated (irradiation amount: 250 mJ/cm ² ) to cure the release agent layer-forming coating liquid to form a release layer, thereby obtaining a release film having a width of 1500 mm.

<Preparation of ceramic slurry>
Barium titanate powder (BaTiO ₃ ; manufactured by Sakai Chemical Industry Co., Ltd., product name “BT-03”) 100 parts by mass, polyvinyl butyral resin as a binder (manufactured by Sekisui Chemical Co., Ltd., product name “S-Lec (registered trademark) B・K BM-2”) 8 parts by mass, 4 parts by mass of dioctyl phthalate as a plasticizer (manufactured by Kanto Chemical Co., Ltd., dioctyl phthalate, deer 1st class), and a mixed solution of toluene and ethanol (mass ratio 6: 4) A ceramic slurry was prepared by mixing 135 parts by mass, dispersing the mixture using a ball mill in the presence of zirconia beads, and removing the beads from the resulting dispersion.

[Uneven defect (evaluation 1)]
The above release film was wound into a roll by the method described in the evaluation of winding properties during high-speed transport, which will be described later. Next, the above ceramic slurry was applied to the surface of the release layer of the release film unwound from the roll release film using a die coater so that the film thickness after drying was 1 μm, over a width of 250 mm and a length of 10 m. coated. After that, the obtained coating film was dried at 80° C. for 1 minute in a dryer. The laminated film of the ceramic green sheet and the release film was illuminated with a fluorescent lamp from the release film side, and the surfaces of all the molded ceramic green sheets were visually inspected, and unevenness defects were evaluated according to the following criteria.

(Convex defect evaluation criteria)
A: No irregularity defects were observed on the ceramic green sheet B: 1 to 5 irregularity defects were observed on the ceramic green sheet C: 6 or more irregularity defects were observed on the ceramic green sheet

[Uneven defect (evaluation 2)]
In the production process of the release film, using a laminated film produced in the same manner as for the uneven defect (evaluation 1), except that a release film produced by changing the time left to stand from 1 week to 3 months was used. , the same evaluation as for the uneven defect (evaluation 1) was performed.

[Winding performance in high-speed transport]
A release film having a width of 1500 mm was produced according to the method for producing a release film described above. A winding test at high speed transport was performed by winding the produced release film under the following conditions.
The release film is transported at a line speed of 80 m / min and a tension of 7 kg / m, and pressed against a contact roll at a pressure of 30 kg / m, onto an ABS (acrylonitrile-butadiene-styrene) resin winding core with a diameter of 6 inches. By winding, a release film having a longitudinal length of 6,000 m was wound into a roll. The rubber hardness of the contact roll measured using a type A durometer was 60 degrees.
The rolled release film roll was visually observed, and from the observation results, the winding property during high-speed transport was evaluated based on the following evaluation criteria.

(Windability evaluation criteria)
A: No winding misalignment was observed.
B: Winding misalignment occurred.

Table 1 shows the production method of the polyester film implemented in each example and each comparative example, the measurement results of the produced polyester film, and each evaluation result.
In Table 1, the "Ratio A" column shows the ratio A (protrusion height/protrusion ratio) obtained for the second main surface of each polyester film, and the "Surface E" column shows the second main surface of each polyester film. It shows the surface free energy of the main surface.

As shown in Table 1, when the release films produced using the polyester films (biaxially oriented polyester films) of Examples 1 to 4 according to the present invention were used to produce ceramic green sheets, Comparative Examples 1 and 2 It was confirmed that the occurrence of unevenness defects can be suppressed compared to

When the surface free energy of the second main surface of the polyester film is 45 mJ / m ² or less, even when a release film produced using a polyester film stored for a long time is used to produce a ceramic green sheet, uneven defects It was confirmed that the occurrence of can be suppressed (comparison with Examples 1 to 4).

It was confirmed that when the ratio A of the polyester film was 0.03 or more, the release film produced using the polyester film had excellent windability during high-speed transport (comparison with Examples 1 to 4).
In addition, it was confirmed that when the protrusion height on the second main surface of the polyester film was 0.3 μm or more, the release film produced using the polyester film had excellent windability during high-speed transport (Example 1 4).

1 polyester film 2 resin layer 3 polyester base material 4 first main surface 5 second main surface 6 projection

Claims

comprising a resin layer and a polyester base material,
having a first principal surface and a second principal surface;
The second main surface is one surface of the resin layer,
The resin layer has protrusions on the surface that is the second main surface,
A polyester film used for producing a release film by forming a release layer on the first main surface,
A polyester film that satisfies the following requirement A.
Requirement A: When observing a region with an area of 10000 μm 2 on the second main surface using a scanning electron microscope and selecting a protrusion with the longest major axis in the region, the above measured using a scanning electron microscope A ratio A of the height of the selected protrusions measured by non-contact surface profilometry using an optical interferometer to the major axis of the selected protrusions is 0.7 or less.
The polyester film according to claim 1, wherein the protrusions are formed of organic particles.
The polyester film according to claim 1, wherein the release film is a release film for manufacturing a ceramic green sheet.
The polyester film according to claim 2, wherein the organic particles contain at least one selected from the group consisting of styrene resins and urethane resins.
2. The polyester film according to claim 1, wherein the second principal surface has a surface free energy of 25 to 45 mJ/m 2 .
The polyester film according to claim 1, wherein the resin layer contains at least one binder selected from the group consisting of acrylic resins, urethane resins and olefin resins.
A region with an area of 10,000 μm 2 on the second main surface is observed using a scanning electron microscope, and the projection having the longest major axis in the region is obtained by performing non-contact surface profile measurement using an optical interferometer. 2. The polyester film according to claim 1, wherein the projection height is 0.3 [mu]m or more.
The polyester film according to claim 1, wherein the polyester film has a thickness of 40 µm or less.
The polyester film according to claim 1, wherein the resin layer has a thickness of 1 to 500 nm.
A method for producing a polyester film according to any one of claims 1 to 9,
Step 1 of longitudinally stretching an unstretched polyester film having a polyester substrate to prepare a uniaxially oriented film;
Step 2 of forming a resin layer on the surface of the uniaxially oriented film using a composition containing organic particles;
and a step 3 of stretching in the width direction while heating the uniaxially oriented film having the resin layer,
Of the temperature of the endothermic peak and the temperature of the baseline shift appearing in the curve showing the change in the amount of heat obtained by measuring the organic particles with a differential scanning calorimeter, the lowest temperature is defined as X, and the uniaxial orientation in the step 3 is defined as X. A method for producing a polyester film, wherein X is lower than Y, where Y is the surface temperature of the film.
The polyester film according to any one of claims 1 to 9,
A release film, comprising a release layer.