JP2023165302A - Release film for the production of ceramic green sheets and method for producing the same, and laminate - Google Patents

Abstract

To provide a release film for production of ceramic green sheets that is capable of producing a ceramic green sheet with reduced unevenness defects and reduced thickness variations, or applications thereof.SOLUTION: A release film for production of ceramic green sheets includes a polyester substrate and a release layer. The release film has a film width of 1 m or more. A thickness of the polyester substrate is at least 40 times of a thickness of the release layer. As measured by differential scanning calorimetry, a pre-peak temperature is 160°C or higher and 225°C or lower. In the width direction of the film, a variation in crystallinity is 5.0% or less. There are also provided a method for producing the release film, and a laminate including the release film.SELECTED DRAWING: None

Description

The present disclosure relates to a release film for producing ceramic green sheets, a method for producing the same, and a laminate.

2. Description of the Related Art As electronic devices become more sophisticated and smaller, electronic components used in electronic devices are also required to have higher performance and become smaller. Among electronic components, for example, the number of mounting points on a board for multilayer ceramic capacitors is increasing, and there is a strong demand for miniaturization.
Manufacturing a multilayer ceramic capacitor generally includes a step of applying a ceramic slurry onto a release layer of a release film and drying it to form a ceramic green sheet.

Patent Document 1 discloses that a polyester film is used as a support film for green sheet molding in the process of manufacturing a multilayer ceramic capacitor, and at least one surface of the film is subjected to infrared spectroscopy measurement (ATR-IR) using the attenuated total reflection method. A _t is the intensity of the absorption peak derived from the trans-conformation polyester obtained by measurement), A g is the intensity of the absorption peak derived from the gauche conformation, and A _g is the intensity of the absorption peak derived from the trans-conformation polyester and the gauche conformation. A polyester film that satisfies the following (1) and (2) is described, where the ratio of the intensity of the absorption peak originating from the locus (trans conformation ratio) is A _t /A _g .
(1) The transformer conformation ratio A _t ^0.5 /A _g ^0.5 in the region from the surface to a depth of 0.5 μm is 1.00 or more and 1.50 or less.
(2) The above transformer conformation ratio A _t ^0.5 /A _g ^0.5 and the transformer conformation ratio A _t ^1.0 /A _g ^1.0 in the region from the surface to a depth of 1.0 μm are as follows. (Formula 1) must be satisfied.
(A _t ^1.0 /A _g ^1.0 )×1.1≦A _t ^0.5 /A _g ^0.5 (Formula 1)

Japanese Patent Application Publication No. 2020-147751

When the present inventors investigated the release film containing a polyester film and a release layer described in Patent Document 1, they found that a ceramic green sheet manufactured using such a release film had minute dents. It was found that shape defects, minute convex defects (hereinafter also referred to as uneven defects), and thickness unevenness occur.

The present disclosure has been made in view of the above circumstances, and the problem to be solved by an embodiment of the present disclosure is to provide a ceramic green sheet that can produce a ceramic green sheet in which unevenness defects are suppressed and thickness unevenness is reduced. An object of the present invention is to provide a release film for producing green sheets.
A problem to be solved by another embodiment of the present disclosure is to provide a laminate including the above release film.
Another object of the present disclosure is to provide a method for producing a release film for producing a ceramic green sheet that can produce a ceramic green sheet in which unevenness defects are suppressed and thickness unevenness is reduced. It is to be.

Means for solving the above problems include the following embodiments.
<1> A release film for producing ceramic green sheets comprising a polyester base material and a release layer,
Having a film width of 1 m or more,
The thickness of the polyester base material is 40 times or more the thickness of the release layer,
The pre-peak temperature measured by differential scanning calorimetry is 160°C or more and 225°C or less,
The variation in crystallinity in the film width direction is 5.0% or less,
Release film for ceramic green sheet production.
<2> In <1>, the variation in the heat shrinkage rate in the direction orthogonal to the film width direction and the variation in the heat shrinkage rate in the film width direction are both 0.03% to 0.50%. Release film for producing ceramic green sheets as described.
<3> The release film for producing ceramic green sheets according to <1> or <2>, which has an intrinsic viscosity (IV) of 0.65 dL/g or more.
<4> The release film for producing a ceramic green sheet according to any one of <1> to <3>, wherein the polyester base material does not substantially contain particles.
<5> Further including a particle-containing layer,
The release film for producing a ceramic green sheet according to any one of <1> to <4>, comprising the release layer, the polyester base material, and the particle-containing layer in this order.
<6> The release film for producing a ceramic green sheet according to <5>, wherein the particle-containing layer contains a non-polyester resin.
<7> The release film for producing a ceramic green sheet according to <6>, wherein the non-polyester resin is at least one resin selected from the group consisting of acrylic resin, urethane resin, and olefin resin.
<8> The release film for producing a ceramic green sheet according to any one of <5> to <7>, wherein the particle-containing layer has a maximum protrusion height Sp of 800 nm or less.
<9> A method for producing a release film for producing a ceramic green sheet comprising a polyester base material and a release layer, the method comprising:
Including a heat setting step of heating a polyester film having a film width of 1 m or more,
In the heat-setting step, the maximum film surface temperature of the polyester film is controlled in the range of 160 ° C. or more and 225 ° C. or less, and the dispersion of the maximum film surface temperature in the film width direction is controlled to be 5.0 ° C. or less. A method for producing a release film for producing ceramic green sheets.
<10> A laminate comprising the release film for producing a ceramic green sheet according to any one of <1> to <8> and a layer containing ceramic.

According to an embodiment of the present disclosure, there is provided a release film for producing ceramic green sheets that can produce ceramic green sheets with suppressed unevenness defects and reduced thickness unevenness.
According to another embodiment of the present disclosure, a laminate including the release film described above is provided.
Further, according to another embodiment of the present disclosure, there is provided a method for producing a release film for producing a ceramic green sheet, which can produce a ceramic green sheet in which unevenness defects are suppressed and thickness unevenness is reduced.

FIG. 2 is a cross-sectional view of a ceramic green sheet obtained using a conventional technique. This is an observed image of a release film with streak-like wrinkles on the surface of the release layer.

Hereinafter, the release film for producing ceramic green sheets, the method for producing the same, and the laminate of the present disclosure will be described in detail. However, the present disclosure is not limited to the following embodiments, and can be implemented with appropriate modifications within the scope of the purpose of the present disclosure.

In this specification, a numerical range expressed using "~" means a range that includes the numerical values written before and after "~" 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 value shown in the Examples.
In this specification, when there are multiple substances corresponding to each component in the composition, unless otherwise specified, the amount of each component in the composition means the total amount of the multiple substances present in the composition. do.
In this specification, the term "process" includes not only an independent process but also a process that is not clearly distinguishable from other processes, as long as the intended purpose of the process is achieved. It will be done.
In this specification, a combination of two or more preferred embodiments is a more preferred embodiment.

In this specification, "a release film having a film width of 1 m or more" means a long release film having a film width of 1 m or more.
Therefore, in this specification, the "longitudinal direction" means the longitudinal direction of a long release film and the polyester base material included in the release film, and the "transport direction" of the release film during production of the release film. and "machine direction".
In this specification, "width direction" means a direction perpendicular to the longitudinal direction. In this specification, "orthogonal" is not limited to strictly orthogonal, but includes substantially orthogonal. "Substantially perpendicular" means that they intersect within a range of 90°±5°, preferably within a range of 90°±3°, and more preferably within a range of 90°±1°. .
Further, in this specification, "film width" means the distance between both ends of the release film in the width direction.

[Release film for ceramic green sheet production]
The release film for producing ceramic green sheets of the present disclosure includes a polyester base material and a release layer. The release film for producing ceramic green sheets of the present disclosure has a film width of 1 m or more, the thickness of the polyester base material is 40 times or more than the thickness of the release layer, and the release film uses differential scanning calorimetry (DSC). The pre-peak temperature measured by scanning calorimetry (hereinafter also referred to as "DSC") is 160° C. or more and 225° C. or less, and the variation in crystallinity in the film width direction is 5.0% or less.
Hereinafter, the release film for ceramic green sheet production will also be simply referred to as a "release film."

The present inventors investigated the polyester film described in Patent Document 1 by forming a release layer as described in Patent Document 1 and using it for manufacturing ceramic green sheets. Through this study, it was found that the polyester film described in Patent Document 1 had good adhesion with the mold release layer after long-term storage, but the polyester film and the mold release layer It has been found that minute concave-shaped defects such as pinholes and convex-shaped defects (i.e., uneven defects) occur in ceramic green sheets manufactured using a release film containing.
It was also discovered that waviness occurs on one surface of the manufactured ceramic green sheet. Specifically, as shown in FIG. 1, on one surface 12 of the obtained ceramic green sheet 10, wavy undulations, that is, concave portions and convex portions are continuous along the film width direction of the release film. A series of shapes could be seen. Furthermore, it was also found that the above-mentioned undulations (that is, a shape in which concave portions and convex portions are continuously connected) caused thickness unevenness throughout the ceramic green sheet. Such uneven thickness of ceramic green sheets is not acceptable because it causes variations in the capacitance of manufactured ceramic capacitors.
The above-mentioned undulations occur on the surface of the ceramic green sheet in contact with the surface of the release layer of the release film, and streak-like wrinkles occur on the surface of the release layer of the release film (i.e., the release surface). caused by. Line-like wrinkles that occur on the surface of the release layer of a release film are wrinkles that extend in a stripe shape along the longitudinal direction of the release film and appear as unevenness in the width direction of the release film. It is observed as an uneven shape extending in the longitudinal direction in a region surrounded by a solid line. Note that the image (photograph) shown in FIG. 2 shows only a part of the observation area on the surface of the release layer of the release film.

According to the release film of the present disclosure, it is possible to produce a ceramic green sheet in which unevenness defects are suppressed and thickness unevenness is reduced. Although the reason for this is not certain, it is assumed as follows.
The release film of the present disclosure has a pre-peak temperature of 160°C or more and 225°C or less as measured by DSC. By setting the DSC pre-peak temperature of the release film to 160°C or higher, it is possible to reduce variations in crystallinity of the release film and differences in heat shrinkage rate, and to reduce thickness unevenness in the film width direction of the release film itself (for example, the above-mentioned It is presumed that line-like wrinkles) are reduced. By using the release film of the present disclosure with reduced thickness unevenness in the film width direction, a ceramic green sheet with reduced thickness unevenness as described above can be manufactured. In addition, by setting the DSC pre-peak temperature of the release film to 225°C or less, it is possible to suppress the formation of oligomers caused by thermal decomposition of the polyester base material, and to suppress the generated oligomers from precipitating on the surface of the release film. It is presumed that it can be done. As a result, it is possible to suppress the occurrence of uneven defects in the ceramic green sheet due to transfer of precipitates on the surface of the release film.
In addition, since the release film of the present disclosure has a variation in crystallinity of 5.0% or less in the film width direction, thickness unevenness (for example, the above-mentioned line-like wrinkles) in the film width direction of the release film itself is reduced. It is assumed that this has been done. In this way, by using the release film of the present disclosure with reduced thickness unevenness in the film width direction, a ceramic green sheet with reduced thickness unevenness as described above can be manufactured.

In the release film of the present disclosure, the thickness of the polyester base material is preferably 40 times or more, preferably 80 times or more, and more preferably 150 times or more than the thickness of the release layer. The thickness of the polyester base material is preferably 4000 times or less the thickness of the release layer.
As described above, since the thickness of the polyester base material is much larger than the thickness of the release layer, the thickness of the polyester base material accounts for a large amount of the thickness of the release film. Therefore, the physical properties of the release film (specifically, the pre-peak temperature measured by DSC, the degree of crystallinity, the heat shrinkage rate, the intrinsic viscosity, etc. described below) have a large influence on the physical properties of the polyester base material. receive.
That is, when the thickness of the polyester base material is 40 times or more greater than the thickness of the release layer, the physical properties of the release film can be controlled by adjusting the physical properties of the polyester base material.

In the release film of the present disclosure, the pre-peak temperature measured by DSC is 160°C to 225°C, and from the viewpoint of manufacturing a ceramic green sheet with suppressed unevenness defects and reduced thickness unevenness, the pre-peak temperature is 160°C to 225°C. It is preferable that it is below ℃. Further, from the viewpoint of producing a ceramic green sheet with suppressed unevenness defects and reduced thickness unevenness, the temperature is preferably 180° C. to 210° C.

In the present disclosure, "pre-peak temperature measured by DSC" is the temperature of the peak that first appears when measured by DSC. Further, the pre-peak temperature corresponds to the highest film surface temperature (also referred to as heat-setting temperature) of the polyester film during heat-setting when obtaining a polyester base material. Therefore, the pre-peak temperature measured by DSC of the release film of the present disclosure mainly depends on the pre-peak temperature measured by DSC of the polyester base material.
The pre-peak temperature of the release film measured by DSC is a value determined by differential scanning calorimetry (DSC) using a conventional method.

In order to set the DSC pre-peak temperature of the release film of the present disclosure to 160°C to 225°C, it is desirable to set the DSC pre-peak temperature of the polyester base material to 160°C to 225°C.

In the release film of the present disclosure, the variation in crystallinity in the film width direction is 5.0% or less, preferably 4.5% or less, and a ceramic green sheet with further reduced thickness unevenness can be produced. From the viewpoint of moisture content, the content is more preferably 4.0% or less, and even more preferably 3.0% or less.
The lower limit of the variation in crystallinity in the film width direction is not particularly limited and may be 0% or more than 0%, but from the viewpoint of manufacturing, it is preferably 0.3% or more. many.
In order to make the variation in crystallinity in the film width direction of the release film of the present disclosure 5.0% or less, the variation in crystallinity in the film width direction of the polyester base material must be 5.0% or less. desirable.

The method for measuring the variation in crystallinity in the film width direction is to measure the total width of the film in the film width direction by measuring one point in the center (at the same distance from both ends of the film in the width direction) and two points at both ends. Cut out three points, measure the crystallinity of the cut sample, and calculate the crystallinity from the center (i.e., the crystallinity at the center in the film width direction) to the crystallinity at both ends (i.e., the crystallinity in the film width direction). It is calculated by subtracting the smaller crystallinity of the crystallinity of the edges. The details of the measurement method and the like are as described in the Examples section.

Variations in crystallinity in the film width direction tend to occur significantly when the film width is 1 m or more. This is because when manufacturing a polyester base material, temperature changes are large at the ends in the width direction of the polyester base material, whereas temperature changes are difficult to occur near the center part in the width direction.
Therefore, by suppressing temperature changes at the ends in the width direction when manufacturing the polyester base material, it is possible to reduce variations in crystallinity in the film width direction.

In the release film of the present disclosure, the variation in heat shrinkage rate in the direction orthogonal to the film width direction and the variation in heat shrinkage rate in the film width direction are both 0.03% to 0.50%. Preferably, from the viewpoint of producing ceramic green sheets with further reduced thickness unevenness, the content is more preferably 0.03% to 0.40%, and even more preferably 0.03% to 0.30%. preferable.
In order to make the variation in the heat shrinkage rate of the release film of the present disclosure in the direction orthogonal to the film width direction and in the film width direction to be 0.03% to 0.50%, it is necessary to It is also desirable that the variation in heat shrinkage rate in the width direction of the film is 0.03% to 0.50%. Furthermore, variations in the thermal shrinkage rate of the polyester base material can be controlled by adjusting variations in the degree of crystallinity of the polyester base material.

The heat shrinkage rate of the release film of the present disclosure is calculated by performing heat treatment at 150° C. for 30 minutes and using the following formula based on the film length of the release film before and after the heat treatment.
Heat shrinkage rate of release film [%] = (Film length before heat treatment - Film length after heat treatment) / (Film length before heat treatment) x 100)

To determine the variation in the heat shrinkage rate of a release film, measure the heat shrinkage rate by cutting out a total of 3 points, 1 point at the center and 2 points at both ends, from the entire width of the film in the film width direction. It is determined from the absolute value of the shrinkage ratio by subtracting the heat shrinkage ratio at both ends of the film in the width direction, which has a larger difference from the heat shrinkage ratio at the center, from the shrinkage ratio. At this time, if the direction in which the film length is measured is the film width direction, the variation in heat shrinkage rate in the film width direction is determined, and the direction in which the film length is measured is in the direction perpendicular to the film width direction (i.e., in the longitudinal direction). direction), the variation in heat shrinkage rate in the direction orthogonal to the film width direction is determined. The details of the measurement method and the like are as described in the Examples section.

The release film of the present disclosure preferably has an intrinsic viscosity (IV) of 0.65 dL/g or more, more preferably 0.65 dL/g to 0.75 dL/g.
It is presumed that when the intrinsic viscosity (IV) of the release film is 0.65 dL/g or more, the polyester molecules become large and difficult to move. Therefore, a release film having an intrinsic viscosity (IV) of 0.65 dL/g or more can suppress the precipitation of oligomers, and can produce ceramic green sheets with suppressed uneven defects.
Intrinsic viscosity can be adjusted by polymerization conditions.

Intrinsic viscosity ( _IV ) is the specific viscosity (η sp =η r −1) obtained by subtracting 1 from the ratio η _r (=η/η ₀ ; relative viscosity) of solution viscosity (η) and solvent viscosity ( _{η 0} ). This is the value obtained by dividing the value by the concentration and extrapolating it to a state where the concentration is zero. Intrinsic viscosity (IV) is calculated from the solution viscosity at 25°C by dissolving polyester in a mixed solvent of 1,1,2,2-tetrachloroethane/phenol (=2/3 [mass ratio]) using an Ubbelohde viscometer. Desired.

<Polyester base material>
The release film of the present disclosure includes a polyester substrate.
A polyester substrate is a film-like object that contains polyester resin as the main polymer component. Here, the term "main polymer component" means a polymer having the highest content (mass) of all polymers contained in the film-like object.
The polyester base material may contain one type of polyester resin alone, or may contain two or more types of polyester resin.

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

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

From the viewpoint of improving the smoothness of the release film, the polyester base material preferably contains substantially no particles. Examples of the particles include particles included in a particle-containing layer described below.
In this specification, "substantially free of particles" means that when a polyester base material is quantitatively analyzed for elements derived from particles by X-ray fluorescence analysis, the content of particles is less than the total mass of the polyester base material. 50 mass ppm or less, preferably 10 mass ppm or less, and more preferably less than the detection limit. This is because even if particles are not actively added to the polyester base material, contaminants derived from foreign substances, raw resin, or dirt attached to the line or equipment in the polyester base material manufacturing process are peeled off and the polyester base material This is because it may be mixed into the base material.

[Properties of polyester base material]
(thickness)
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, from the viewpoint of controlling releasability. The lower limit of the thickness is not particularly limited, but from the viewpoint of improving strength and workability, it is preferably 3 μm or more, more preferably 10 μm or more, and even more preferably 20 μm or more.
The thickness of the polyester base material can be determined by preparing a section with a cross section perpendicular to the main surface of the release film and using a scanning electron microscope (SEM) or transmission electron microscope (TEM). This is the arithmetic mean value of the thicknesses of the above section measured at five locations.

The method for producing the polyester base material and the details of the polyester resin contained in the polyester base material will be described in detail in the section of the method for producing a release film of the present disclosure.

<Peeling layer>
The release layer is provided to enable the release film to be peeled off.
The ceramic green sheet is formed on the release surface of the release layer (ie, the surface of the release layer opposite to the polyester base material). That is, the ceramic green sheet is manufactured to be releasable on the release surface of the release film.
Note that the release layer may be provided directly on the surface of the polyester base material or may be provided on the polyester base material via another layer, but from the viewpoint of better smoothness, it may be provided directly on the surface of the polyester base material. It is preferable to provide one.

The structure of the release layer is not particularly limited as long as the ceramic green sheet can be manufactured in a removable manner as described above, but it is preferable that the release layer contains a release agent.

The components contained in the release layer will be described in detail below.

[paint remover]
Examples of the release agent include, but are not limited to, silicone resins, fluororesins, alkyd resins, and various waxes. Further, the release agent is preferably a resin, and a silicone resin is preferred from the viewpoint of superior releasability of the ceramic green sheet.
It is preferable that the release agent has a crosslinked structure. That is, the release layer is preferably a crosslinked film.
In order to form a release agent having a crosslinked structure, a method of forming a release layer using a composition for forming a release layer containing a crosslinking agent may be mentioned, as described below.

Silicone resin means a resin having a silicone structure in its molecule. Examples of the silicone resin include curable silicone resins, silicone graft resins, and modified silicone resins such as alkyl-modified silicone resins, with reactive curable silicone resins being preferred.
Examples of the reactive curable silicone resin include addition reaction silicone resins, condensation reaction silicone resins, and ultraviolet or electron beam curable silicone resins.

Examples of addition reaction silicone resins include resins obtained by curing polydimethylsiloxane having a vinyl group introduced into the terminal or side chain and hydrogensiloxane by reacting them using a platinum catalyst.
As a condensation reaction type silicone resin, for example, a three-dimensional silicone resin formed by condensing polydimethylsiloxane having an OH group at the end and polydimethylsiloxane having an H group at the end using an organotin catalyst. Examples include resins having a crosslinked structure.
UV-curable silicone resins include those that utilize the same radical reaction as silicone rubber crosslinking, those that introduce unsaturated groups and are photo-cured, and those that decompose onium salts with UV or electron beams to generate strong acids and produce epoxy resins. Examples include those that are crosslinked by cleaving a group, and those that are crosslinked by addition reaction of thiol to vinylsiloxane. More specifically, acrylate-modified polydimethylsiloxane and glycidoxy-modified polydimethylsiloxane are mentioned.

[Other resins]
In addition to the above resin as the release agent, the release layer may contain a resin other than the release agent (hereinafter also referred to as "other resin").
As other resins, known resins can be used. Other resins include, for example, ultraviolet curable resins and thermosetting resins, which are suitable for in-line coating and can produce ceramic green sheets with more suppressed unevenness defects and reduced thickness unevenness. From this point of view, thermosetting resins are preferred. Specific examples of the thermosetting resin include acrylic resin, unsaturated polyester resin, melamine resin, epoxy resin, phenol resin, olefin resin, and urethane resin. Preferred are resins, urethane resins, and olefin resins.
In addition, in the composition for forming a release layer described below, it may contain another resin or a compound that is a raw material for synthesizing another resin, and a polymerization initiator and/or a catalyst, and the release layer may contain, It may also contain residues of a polymerization initiator and/or catalyst.

[Additive]
The release layer may contain additives in addition to the resin as the release agent and other resins. Examples of additives include surfactants, light release additives and heavy release additives for adjusting release force, adhesion improvers, and antistatic agents.

The release agents contained in the release layer may be used alone or in combination of two or more.
The content of the release agent in the release layer is preferably 0.1% by mass to 98% by mass, more preferably 0.5% by mass to 50% by mass, based on the total mass of the release layer.
The content of other resins in the release layer is preferably 0% to 98% by weight, more preferably 1% to 95% by weight, based on the total weight of the release layer.
The remainder other than the resin as a release agent and other resins in the release layer may be residues of the above-mentioned additives, solvents, polymerization initiators, catalysts, etc. contained in the composition for forming a release layer.

[Properties of release layer]
(thickness)
The thickness of the release layer is preferably 10 nm to 1000 nm, more preferably 30 nm to 700 nm, from the viewpoint of achieving a well-balanced release performance and surface smoothness of the release layer.
The thickness of the release layer is determined by preparing a section having a cross section perpendicular to the main surface of the release film, and measuring the thickness using a scanning electron microscope (SEM) or a transmission electron microscope (TEM). This is the arithmetic mean value of the thickness at each location.

(Surface free energy of peeled surface)
The surface free energy of the surface of the release layer (ie, release surface) is preferably 5 mJ/m ² to 50 mJ/m ² , more preferably 10 mJ/m ² to 35 mJ/m ² .
When the surface free energy of the peeling surface is within the above range, the ceramic green sheet is easily peeled off, and the coating properties of the ceramic slurry when manufacturing the ceramic green sheet are improved.
The surface free energy of the release surface can be adjusted by the type of resin and additives forming the release layer.

The surface free energy of the peeled surface was measured using a contact angle meter (for example, "DROPMASTER-501" manufactured by Kyowa Interface Science Co., Ltd.) under conditions of 25°C. It is determined by dropping a glycol droplet, measuring the contact angle one second after the droplet adheres to the surface, and calculating from each of the obtained contact angles according to 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.

(Maximum protrusion height Sp of peeled surface, surface average roughness Sa)
From the viewpoint of smoothing the ceramic green sheet produced on the peeling surface, it is preferable that the peeling surface is as smooth as possible. Specifically, the maximum protrusion height Sp of the peeled surface is preferably 1 nm to 60 nm, more preferably 1 nm to 40 nm.
Further, the surface average roughness Sa of the peeled surface is preferably 0 nm to 10 nm, more preferably 0 nm to 5 nm, and even more preferably 0 nm to 2 nm.
The maximum protrusion height Sp and surface average roughness Sa of the release surface can be adjusted by not including particles in the release layer when providing the release layer, and by selecting the resin and additives that form the release layer.

The maximum protrusion height Sp and surface average roughness Sa of the peeled surface were determined by measuring the surface of the peeled surface using an optical interferometer ("Vertscan 3300G Lite" manufactured by Hitachi High-Tech Corporation) under the following conditions. After that, it is determined by analysis using the built-in data analysis software.
To measure the maximum protrusion height Sp, measure 5 times at different measurement positions, and take the maximum value of the obtained measurement value as the measured value of the maximum protrusion height Sp (indicated as P in the built-in data analysis software). ). Further, in the measurement of the surface average roughness Sa, the measurement is performed five times while changing the measurement position, and the average value of the obtained measurement values is taken as the measured value of the surface average roughness Sa. The specific measurement conditions are as follows.
Measurement mode: WAVE mode Objective lens: 50x Measurement area: 186μm x 155μm

<Particle-containing layer>
The release film of the present disclosure preferably further includes a particle-containing layer, and more preferably includes a release layer, a polyester base material, and a particle-containing layer in this order.

The particle-containing layer refers to a layer containing particles.
When the release film is provided with a particle-containing layer, the transportability of the release film can be improved. Specifically, in the release film, it is possible to improve the winding quality (suppress blocking), suppress the occurrence of scratches and defects during transportation, and reduce transportation wrinkles during high-speed transportation.

The particle-containing 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, but from the viewpoint of better adhesion, it is preferable to provide the particle-containing layer directly on the surface of the polyester base material. It is preferable to provide one.

Further, the particle-containing layer preferably contains particles and a binder, and may further contain additives.

The particles, binder, and additives will be explained below.

(particle)
The average particle diameter of the particles contained in the particle-containing layer is not particularly limited, and is preferably 10 nm to 2 μm, more preferably 30 nm to 1.5 μm, and 30 nm to 1.5 μm from the viewpoint of better transportability and suppressing transfer marks. 500 nm is more preferred.
In addition, from the viewpoint of better transportability and the ability to suppress transfer marks, the average particle diameter of the particles contained in the particle-containing layer is 10 nm to 200 nm (more preferably 30 nm to 130 nm), and the thickness of the particle-containing layer is 1 nm. ~200 nm (more preferably 10 nm ~ 100 nm), and the average particle diameter of the particles is preferably larger than the thickness of the particle-containing layer.

As the particles contained in the particle-containing layer, one type of particles may be used alone, or two or more types of particles may be used.
When the particle-containing layer contains two or more types of particles with different particle sizes, it is preferable that the particle-containing layer contains at least one type of particles with an average particle size within the above range, and two or more types of particles with different particle sizes. It is more preferable that all particles have an average particle diameter within the above range.

Examples of the particles contained in the particle-containing layer include organic particles and inorganic particles. Among these, organic particles are preferred from the viewpoint of suppressing the defective rate of ceramic capacitors manufactured using the obtained ceramic green sheets when the ceramic green sheets are manufactured.
As the organic particles, resin particles are preferred. Examples of the resin constituting the resin particles include acrylic resins such as polymethyl methacrylate resin (PMMA), polyester resins, silicone resins, styrene resins, and styrene-acrylic resins. The resin particles may have a crosslinked structure. Examples of the resin particles having a crosslinked structure include divinylbenzene crosslinked particles.
Note that in the present disclosure, acrylic resin means a resin containing a structural unit derived from acrylate or methacrylate.
Examples of the inorganic particles include silica particles (also referred to as silicon dioxide particles), titania particles (also referred to as titanium oxide particles), calcium carbonate, barium sulfate, and alumina particles (also referred to as aluminum oxide particles). Among these, the inorganic particles are preferably silica particles from the viewpoint of further improving haze and durability.

The shape of the particles is not particularly limited, and includes, for example, rice grain shape, spherical shape, cube shape, spindle shape, scale shape, aggregate shape, and irregular shape. Agglomerated state means a state in which primary particles are aggregated. Although the shape of the aggregated particles is not limited, spherical or irregular shapes are preferred.

As the agglomerated particles, fumed silica particles are preferred. Examples of commercially available products include the Aerosil series manufactured by Nippon Aerosil Co., Ltd.
Colloidal silica particles are preferred as non-agglomerated particles. Examples of commercially available products include the Snowtex (registered trademark) series manufactured by Nissan Chemical Co., Ltd.

From the viewpoint of transportability, the content of particles in the particle-containing layer is preferably 0.1% by mass to 30% by mass, more preferably 1% by mass to 25% by mass, and 1% by mass. More preferably 15% by mass.
Further, the content of particles is preferably 0.0001% by mass to 0.01% by mass, more preferably 0.0005% by mass to 0.005% by mass, based on the total mass of the release film.

(Non-polyester resin (binder))
Preferably, the particle-containing layer contains a non-polyester resin. The non-polyester resin contained in the particle-containing layer has a function as a binder.

Non-polyester resin means resin other than polyester resin. Specifically, the non-polyester resin is preferably at least one selected from the group consisting of acrylic resin, urethane resin, olefin resin, polyvinyl alcohol resin, styrene butadiene resin, and acrylonitrile butadiene resin, and acrylic resin, Preferably, the resin is at least one resin selected from the group consisting of urethane resins and olefin resins.

Here, non-polyester resins (especially acrylic resins, urethane resins, and olefin resins) and polyester resins have different solubility parameters (SP values). In other words, since the compatibility of the acrylic resin, urethane resin, and olefin resin with the polyester resin is insufficient, impurities such as oligomers are difficult to precipitate from the polyester base material via the particle-containing layer onto the conveying surface. It is presumed that this makes it difficult for protrusions caused by impurities contained in the polyester base material to form on the conveying surface.

The above-mentioned non-polyester resins such as acrylic resins, urethane resins, and olefin resins are not particularly limited, and known resins can be used.
The non-polyester resin is preferably an acid-modified resin, that is, an acid group-containing non-polyester resin.
Moreover, the particle-containing layer may contain polyester resin.

The acrylic resin is a resin containing structural units derived from (meth)acrylate, and may be copolymerized with a vinyl monomer such as styrene. The acrylic resin is not particularly limited, but preferably contains a structural unit derived from a (meth)acrylate having an alkyl group having 1 to 12 carbon atoms; It is more preferable to include a structural unit derived from the above.
The acrylic resin may have an acid-modified component. The acrylic resin may contain a structural unit derived from (meth)acrylic acid as an acid-modified component. Further, (meth)acrylic acid may form an acid anhydride, or may be neutralized with at least one selected from alkali metals, organic amines, and ammonia.

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 from the viewpoint of application as an aqueous dispersion, it is preferably 2 mgKOH/g or more. By setting the acid value of the acrylic resin within the above range and/or by including a structural unit derived from a (meth)acrylate having an alkyl group having 1 to 12 carbon atoms, the resin becomes even more difficult to be compatible with the polyester resin. This can further suppress impurities such as oligomers contained in the polyester base material from precipitating in the particle-containing layer, thereby further suppressing unevenness defects in the ceramic green sheet.

The olefin resin may be any resin containing a structural unit derived from an olefin in its main chain. By having a structural unit derived from an olefin in the main chain, the resin can be made difficult to be compatible with polyester resin, and impurities such as oligomers contained in the polyester base material are suppressed from precipitating in the particle-containing layer. It is possible to suppress unevenness defects in ceramic green sheets.
The olefin is not particularly limited, but alkenes having 2 to 6 carbon atoms are preferred, ethylene, propylene, or hexene are more preferred, and ethylene is even more preferred.
The olefin-derived structural units of the polyolefin are preferably 50 mol% to 99 mol%, more preferably 60 mol% to 98 mol%, based on all the structural units of the polyolefin.

As the olefin resin, acid-modified olefin resin is preferred. Examples of the acid-modified olefin resin include copolymers obtained by modifying the above olefin resin with an acid-modifying component such as an unsaturated carboxylic acid or its anhydride.

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. and Chemipearl (registered trademark) series such as SA100 (manufactured by Mitsui Chemicals, Ltd.), Hitech (registered trademark) series such as Hitec S3121 and S3148K (manufactured by Toho Chemical Co., Ltd.), Arrowbase SE-1013, SE-1010, Arrowbase (registered trademark) series (manufactured by Unitika Co., Ltd.) such as SB-1200, SD-1200, SD-1200, DA-1010 and DB-4010, Hardren AP-2, NZ-1004 and NZ-1005 (manufactured by Toyobo Co., Ltd.) (manufactured by Sumitomo Seika Co., Ltd.), as well as Sepolsion G315 and VA407 (manufactured by Sumitomo Seika Co., Ltd.).
Furthermore, acid-modified olefin resins described in [0022] to [0034] of JP-A No. 2014-076632 can also be preferably used.

The polymer is not limited as long as it has a urethane bond in its main chain, and any known urethane resin such as a reaction product of a polyisocyanate compound and a polyol compound can be used.
From the viewpoint of ease of forming a film by coating, the urethane resin is preferably a urethane resin having an acidic group, or a form containing a urethane resin and a dispersant. Examples of acidic groups include carboxyl groups.
For example, urethane resin can be made into a resin that is not easily compatible with polyester resin by adjusting the structure and hydrophobicity (hydrophilicity) of the raw material polyol compound and/or isocyanate compound. The precipitation of impurities such as oligomers contained in the particles in the particle-containing layer is suppressed, and uneven defects in the ceramic green sheet can be suppressed. From the viewpoint of further suppressing unevenness defects, the urethane resin preferably includes a polyester structure.
Commercially available urethane resins include, for example, Hydran (registered trademark) AP-20, AP-40N, and AP-201 (manufactured by DIC Corporation), Takelac (registered trademark) W-605, W-5030, and W. -5920 (manufactured by Mitsui Chemicals, Inc.), Superflex (registered trademark) 210 and 130, and Elastron (registered trademark) H-3-DF, E-37 and H-15 (manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd.) Co., Ltd.).

The non-polyester resin contained in the particle-containing layer may have a crosslinked structure. That is, the particle-containing layer may be a crosslinked film.
In order to form a non-polyester resin having a crosslinked structure, there is a method of forming a particle-containing layer using a particle-containing layer forming composition containing a crosslinking agent, as described below.

The particle-containing layer may contain one type of binder alone, or may contain two or more types of binders. Further, the particle-containing layer may contain one type of non-polyester resin, or may contain two or more types of non-polyester resin.
The content of the binder (preferably non-polyester resin) is preferably 30% by mass to 99.8% by mass, and 50% by mass to 99.5% by mass, based on the total mass of the particle-containing layer, from the viewpoint of suppressing unevenness defects. Mass% is more preferred.

(Additive)
The particle-containing layer may contain additives other than the above particles and binder.
Examples of additives contained in the particle-containing layer include surfactants, waxes, antioxidants, ultraviolet absorbers, colorants, reinforcing agents, plasticizers, antistatic agents, flame retardants, rust preventives, and Examples include mold agents.

The particle-containing layer preferably contains a surfactant from the viewpoint of improving the smoothness of areas other than the areas where protrusions formed by particles are present on the conveying surface.
The surfactant is not particularly limited, and includes silicone surfactants, fluorine surfactants, and hydrocarbon surfactants. Among these, the surfactant is preferably a hydrocarbon surfactant.

The silicone 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.
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), as well as KF-351A, KF-352A, KF-353, KF-354L, KF-355A, KF-615A, KF-945, KF-640, KF-642, Examples include KF-643, KF-6020, X-22-4515, KF-6011, KF-6012, KF-6015, and KF-6017 (all manufactured by Shin-Etsu Chemical Co., Ltd.).

The fluorine-based surfactant 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 Megafac (registered trademark) F-114, F-410, F-440, F-447, F-553, and F-556 (all of which are 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 S-386 (manufactured by AGC Seimi Chemical Co., Ltd.).
In addition, from the viewpoint of improving environmental suitability, fluorine-based surfactants have a linear perfluoroalkyl group with a carbon number of 7 or more, such as perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS). Preference is given to using surfactants derived from alternative materials of compounds.

Examples of the hydrocarbon surfactant include anionic surfactants, nonionic surfactants, cationic surfactants, and amphoteric surfactants.
Examples of anionic surfactants include alkyl sulfates, alkylbenzenesulfonates, alkyl phosphates, and fatty acid salts.
Examples of the nonionic surfactant include polyalkylene glycol mono- or dialkyl ether, polyalkylene glycol mono- or dialkyl ester, and polyalkylene glycol mono- or dialkyl ester/monoalkyl ether.
Examples of the cationic surfactant include primary to tertiary alkylamine salts and quaternary ammonium compounds.
Examples of amphoteric surfactants include surfactants having both an anionic site and a cationic site in the molecule.

Commercially available anionic surfactants include, for example, Rapizol (registered trademark) A-90, A-80, BW-30, B-90, and C-70 (all manufactured by NOF Corporation); NIKKOL (registered trademark) OTP-100 (manufactured by Nikko Chemical Co., Ltd.), Kohakuol (registered trademark) ON, L-40, and Phosphanol (registered trademark) 702 (manufactured by Toho Chemical Co., Ltd.) ), Viewlite (registered trademark) A-5000, and SSS (manufactured by Sanyo Chemical Industries, 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: Kyukyu Alcohol Industries) Co., Ltd.), EMALEX (registered trademark) ET-2020 (manufactured by Nippon Emulsion Co., Ltd.), Surfynol (registered trademark) 104E, 420, 440, 465, and Dynor (registered trademark) 604, 607 (manufactured by Nissin Chemical Industry Co., Ltd.).

Among the hydrocarbon surfactants, anionic surfactants and/or nonionic surfactants are preferred, and anionic surfactants are more preferred.

The anionic hydrocarbon surfactant preferably has a plurality of hydrophobic end groups from the viewpoint of further improving smoothness. The hydrophobic terminal group may be a part of the hydrocarbon group that the hydrocarbon surfactant has. For example, a hydrocarbon surfactant having a branched hydrocarbon group at its end has a plurality of hydrophobic end groups.
Examples of anionic hydrocarbon surfactants having multiple hydrophobic end groups include di-2-ethylhexyl sodium sulfosuccinate (having four hydrophobic end groups) and di-2-ethyl octyl sodium sulfosuccinate (having four hydrophobic end groups). (having four hydrophobic end groups) and branched alkylbenzene sulfonates (having two hydrophobic end groups).

One type of surfactant may be used, or two or more types may be used in combination.
When the particle-containing layer contains a surfactant, the content of the surfactant is preferably 0.1% by mass to 10% by mass based on the total mass of the particle-containing layer, and from the viewpoint of better surface smoothness, 0. .1% to 5% by weight is more preferable, and even more preferably 0.5% to 2% by weight.

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

[Properties of particle-containing layer]
(thickness)
For example, when the particle-containing layer is formed by applying a composition containing particles and a non-polyester resin onto one side of a polyester film, the thickness of the particle-containing layer is often 1 μm or less.
Further, when a polyester film having a laminated particle-containing layer is formed by coextrusion molding, the thickness of the particle-containing layer is often 1 μm to 10 μm.
The thickness of the particle-containing layer is preferably 1 nm to 3 μm, and when manufactured by coating, from the viewpoint of manufacturing suitability and haze reduction, the thickness is preferably 1 nm to 500 nm, more preferably 1 nm to 250 nm, even more preferably 10 nm to 100 nm, Particularly preferred is 20 nm to 100 nm.
The thickness of the particle-containing layer is determined by preparing a section having a cross section perpendicular to the main surface of the release film, and measuring the thickness of the section using a scanning electron microscope (SEM) or a transmission electron microscope (TEM). The arithmetic mean value of the thickness at five locations.

(Surface free energy of particle-containing layer)
The surface free energy at the surface of the particle-containing layer (that is, the surface of the particle-containing layer opposite to the polyester base material) is preferably 25 mJ/m ² to 65 mJ/m ² , and preferably 25 mJ/m ² to 60 mJ/m ² . It is preferably 25 mJ/m ² to 50 mJ/m ² , more preferably 30 mJ/m ² to 45 mJ/m ² .
By having the surface free energy on the surface of the particle-containing layer within the above range, it is possible to suppress impurities such as oligomers contained in the polyester base material from precipitating in the particle-containing layer, and to suppress unevenness defects in the ceramic green sheet. can.
Note that the oligomer is a component contained as an impurity in the polyester base material, which is a low molecular weight by-product produced during the polymerization of polyester.

(Maximum protrusion height Sp of particle-containing layer, surface average roughness Sa)
From the viewpoint of further suppressing unevenness defects in the ceramic green sheet during production of the ceramic green sheet, the maximum protrusion height Sp on the surface of the particle-containing layer is preferably 800 nm or less. In particular, when the particle-containing layer contains inorganic particles, the maximum protrusion height Sp on the surface of the particle-containing layer is preferably 300 nm or less. Although the lower limit of the maximum protrusion height Sp is not particularly limited, it is preferably 10 nm or more.
Further, the surface average roughness Sa of the surface of the particle-containing layer is preferably 0 nm to 10 nm, more preferably 0 nm to 5 nm, and even more preferably 1 nm to 3 nm.
The method for measuring the maximum protrusion height Sp and surface average roughness Sa of the surface of the particle-containing layer is the same as the method for measuring the maximum protrusion height Sp and surface average roughness Sa of the peeled surface described above.

<Properties of release film>
[Thickness]
The thickness of the release 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 releasability. Further, the thickness of the release film is preferably 3 μm or more, more preferably 10 μm or more, and even more preferably 20 μm or more, from the viewpoint of improving strength and processability.
The thickness of the release film was measured using a continuous stylus film thickness meter. The details of the measurement method and the like are as described in the Examples section.

[Manufacturing method of release film]
A method for manufacturing a release film of the present disclosure will be described.
The method for producing the release film of the present disclosure is not particularly limited as long as the release film of the present disclosure described above can be obtained, and known methods may be used.

Among these, preferred methods for producing release films from the viewpoint of producing release films with high productivity include:
an extrusion molding step of forming an unstretched polyester film by extrusion molding;
A first stretching step of stretching an unstretched polyester film in either one of the transport direction and the width direction to form a uniaxially stretched polyester film, and a uniaxially stretched polyester film in the other of the transport direction and the width direction. a second stretching step of stretching to form a biaxially stretched polyester film, stepwise or simultaneously;
Between the extrusion molding step and the stretching step, between the first stretching step and the second stretching step, or after the stretching step, a release layer forming composition is applied to one side of the polyester film to form a release layer. The manufacturing method includes a step of forming a release layer.

By the above manufacturing method, a release film including a polyester base material and a release layer is obtained. That is, the polyester base material in the obtained release film is preferably a film obtained by stretching an unstretched polyester film in both the transport direction and the width direction, that is, a biaxially stretched polyester film.

In addition, in the method for producing a release film of the present disclosure, particles are attached to the other side of the polyester film between the extrusion molding step and the stretching step, between the first stretching step and the second stretching step, or after the stretching step. Preferably, the method further includes a step of forming a particle-containing layer by applying a composition for forming a particle-containing layer.

By the above manufacturing method, a release film containing a release layer, a polyester base material, and a particle-containing layer in this order is obtained.

The method for producing a release film of the present disclosure preferably has the following embodiments, for example.
In a preferred embodiment, in addition to the above-mentioned extrusion molding step, stretching step, release layer forming step, and particle-containing layer forming step performed as necessary,
a heat setting step of heating and heat setting the stretched polyester film in the drawing step;
A heat relaxation step in which the polyester film heat-set in the heat-setting step is heated at a lower temperature than the heat-setting step to thermally relax it;
a cooling process of cooling the polyester film thermally relaxed by the thermal relaxation process;
It is preferable to include.
In a preferred embodiment, the heat setting temperature in the heat setting step, the heat relaxation temperature in the heat relaxation step, and the cooling rate of the polyester film in the cooling step are each within the ranges described below, so that the surface of the release layer of the release film (i.e. This makes it easier to suppress streak-like wrinkles that occur on the peeled surface. By suppressing streak-like wrinkles that occur on the surface of the release layer of the release film, it is possible to suppress uneven thickness of ceramic green sheets produced using such a release film.
That is, from the viewpoint of manufacturing a ceramic green sheet with more suppressed thickness unevenness, it is desirable to manufacture a release film in the above-mentioned preferred embodiment.

Each step in a preferred embodiment of the method for producing a release film of the present disclosure will be described below. Note that the method for producing a release film of the present disclosure is not limited to one preferred embodiment, and the following steps can be omitted as appropriate.

[Extrusion molding process]
The extrusion molding process is a process of forming an unstretched polyester film by extrusion molding.
More specifically, it is a step of extruding a molten resin containing a raw material polyester resin into a film to form an unstretched polyester film.

The extrusion molding method is a method of molding raw resin into a desired shape by extruding a melt of the raw resin using, for example, an extruder.
The melt extruded from the extrusion die is cooled and shaped into a film. For example, the melt can be formed into a film by bringing the melt into contact with a casting roll and cooling and solidifying the melt on the casting roll. In cooling the melt, it is further preferable to apply wind (preferably cold air) to the melt.

The polyester resin used in this step will be explained below.
In order to produce a polyester base material that is substantially free of particles, it is preferable to use polyester resin pellets that do not contain particles during extrusion molding.

(polyester resin)
The polyester resin used in this step is synthesized by copolymerizing a dicarboxylic acid component and a diol component.
In addition, the polyester resin is a polyfunctional monomer in which the sum of the number of carboxylic acid groups (a) and the number of hydroxyl groups (b) (a+b) is 3 or more (hereinafter referred to as "trifunctional or higher polyfunctional monomer" or simply " It is preferable that the monomer contains a structural unit derived from a polyfunctional monomer (also referred to as a polyfunctional monomer).

The polyester resin can be obtained, for example, by subjecting a dicarboxylic acid component and a diol component to an esterification reaction and/or transesterification reaction using a well-known method. Obtained by polymerization.
Further, the polyester resin may have a structure derived from an end capping agent introduced therein.

The dicarboxylic acid component, diol component, polyfunctional monomer, and terminal capping agent will be explained below.

-Dicarboxylic acid component-
Examples of the dicarboxylic acid component 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. Examples include esters. Among these, aromatic dicarboxylic acid or methyl aromatic dicarboxylate is preferred.

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.
Examples of the alicyclic dicarboxylic acid compound include adamantane dicarboxylic acid, norbornene dicarboxylic acid, cyclohexane dicarboxylic acid, and decalin dicarboxylic acid.

Examples of aromatic dicarboxylic acid compounds include terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalene dicarboxylic acid, 1,5-naphthalene dicarboxylic acid, 2,6-naphthalene dicarboxylic acid, and 1,8-naphthalene dicarboxylic acid. , 4,4'-diphenyl dicarboxylic acid, 4,4'-diphenyl ether dicarboxylic acid, 5-sodium sulfoisophthalic acid, phenylindane dicarboxylic acid, anthracene dicarboxylic acid, phenanthrene dicarboxylic acid, and 9,9'-bis(4- (carboxyphenyl)fluorenic acid and methyl esters thereof.
Among these, terephthalic acid or 2,6-naphthalene dicarboxylic acid is preferred, and terephthalic acid is more preferred.

One type of dicarboxylic acid component may be used, or two or more types may be used in combination. When terephthalic acid is used as the dicarboxylic acid compound, it may be used alone or in combination with other aromatic dicarboxylic acids such as isophthalic acid or aliphatic dicarboxylic acids.

-Diol component-
Examples of the diol component include aliphatic diol compounds, alicyclic diol compounds, and aromatic diol compounds, and among them, aliphatic diol compounds are 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 Mention may be made of pentyl glycol, with ethylene glycol being preferred.
Examples of the alicyclic diol compound include cyclohexanedimethanol, spiroglycol, and isosorbide.
Examples of the aromatic diol compound include bisphenol A, 1,3-benzenedimethanol, 1,4-benzenedimethanol, and 9,9'-bis(4-hydroxyphenyl)fluorene.

One type of diol component may be used, or two or more types may be used in combination.

-Polyfunctional monomer-
Examples of polyfunctional monomers include carboxylic acids having a carboxylic acid group number (a) of 3 or more, their ester derivatives and acid anhydrides, polyfunctional monomers having a hydroxyl group number (b) of 3 or more, and Examples include oxyacids having both a hydroxyl group and a carboxylic acid group, and the total number (a) of the number of carboxylic acid groups and the number of hydroxyl groups (b) (a+b) is 3 or more.
As the polyfunctional monomer, oxyacids such as l-lactide, d-lactide, hydroxybenzoic acid, derivatives thereof, or compounds in which a plurality of such oxyacids are linked are added to the carboxy terminal of the polyfunctional monomer. Also suitable are

Regarding the structural units derived from polyfunctional monomers and their content, the contents described in [0037] to [0039] of JP 2013-047317 can also be referred to, and the contents of the above publication are incorporated into the present specification. .
As the polyfunctional monomer, polyfunctional monomers described in [0068] to [0072] of JP-A-2013-047317 can also be used, and the contents of the above publication are incorporated into the present specification.

One type of polyfunctional monomer may be used, or two or more types may be used in combination.

-Terminal sealing agent-
When obtaining a polyester resin, a terminal capping agent may be used if necessary. By using the terminal capping agent, a structure derived from the terminal capping agent is introduced at the end of the polyester resin.
The terminal capping agent is not limited, and any known terminal capping agent can be used. Examples of the terminal capping agent include oxazoline compounds, carbodiimide compounds, and epoxy compounds.
As for the terminal capping agent, the contents described in [0055] to [0064] of JP-A No. 2014-189002 and [0040] to [0051] of JP-A No. 2013-047317 can also be referred to; , the contents of which are incorporated herein.

One type of terminal capping agent may be used, or two or more types may be used in combination.

-Production of polyester resin-
When producing polyester resin, as mentioned above, esterification reaction and/or transesterification reaction are used.
The resulting polyester resin includes polyethylene terephthalate (PET) and polyethylene-2,6-naphthalate (PEN), with PET being preferred. Also, among PET, those polymerized using one or more types selected from germanium (Ge)-based catalysts, antimony (Sb)-based catalysts, aluminum (Al)-based catalysts, and titanium (Ti)-based catalysts. are preferred, and those polymerized using a Ti-based catalyst are more preferred.

Hereinafter, one preferred embodiment of the method for producing polyester resin will be described. The method for producing polyester resin is not limited to this preferred embodiment.
A preferred embodiment of the method for producing a polyester resin includes an esterification reaction step for obtaining an esterification reaction product using at least a dicarboxylic acid component and a diol component, and a polymerization step for producing an esterification reaction product obtained in the esterification reaction step. A polycondensation reaction step of performing a condensation reaction to obtain a polycondensate.

- Esterification reaction step In the esterification reaction step, a dicarboxylic acid component and a diol component are polymerized in the presence of a catalyst.
Specifically, first, the dicarboxylic acid component and the diol component are mixed with an organic chelate titanium complex, which is a Ti-based catalyst, prior to adding the magnesium compound and the phosphorus compound. Ti-based catalysts such as organic chelate titanium complexes are preferred because they have high catalytic activity for esterification reactions. At this time, the Ti-based catalyst may be added to the mixture of the dicarboxylic acid component and the diol component, or the dicarboxylic acid component (or diol component) and the Ti-based catalyst may be mixed and then the diol component (or dicarboxylic acid component) is added. May be mixed. Further, the dicarboxylic acid component, the diol component, and the Ti-based catalyst may be mixed at the same time. There are no particular restrictions on the mixing method, and any conventionally known method can be used.

Preferred examples of the Ti-based catalyst used in the esterification reaction step include organic chelate titanium complexes having an organic acid as a ligand. Here, examples of the organic acid serving as a ligand include citric acid, lactic acid, trimellitic acid, and malic acid. Among these, as the Ti-based catalyst, an organic chelate complex having citric acid or a citrate as a ligand is preferable.
Further, as the Ti-based catalyst, the Ti-based catalyst described in [0080] of JP-A No. 2013-047317 and the titanium compounds described in [0082] to [0084] and [0086] can be used. The contents are incorporated herein.

When polymerizing polyester, the Ti-based catalyst is preferably used so that the concentration in the system is 1 ppm to 50 ppm, more preferably 2 ppm to 30 ppm, and even more preferably 3 ppm to 15 ppm, in terms of titanium element. By using the Ti-based catalyst in this amount, the polyester resin contains titanium element in an amount of 1 ppm or more and 50 ppm or less.

In the esterification reaction step, a magnesium compound as an additive is added to a system in which a Ti-based catalyst (for example, an organic chelate titanium complex) is present in addition to a dicarboxylic acid component and a diol component, and then a magnesium compound as an additive is added. Preferably, a phosphorus compound is added.

Examples of the magnesium compound as an additive include magnesium salts such as magnesium oxide, magnesium hydroxide, magnesium alkoxide, magnesium acetate, and magnesium carbonate. Among these, magnesium acetate is preferred from the viewpoint of solubility in ethylene glycol.

The magnesium compound is preferably used so that the concentration in the system is 50 ppm or more, preferably 50 ppm to 100 ppm, more preferably 60 ppm to 90 ppm, still more preferably 70 ppm to 80 ppm, in terms of Mg element.

The phosphorus compound used as an additive is preferably a pentavalent phosphorus compound, and more preferably a pentavalent phosphoric acid ester having no aromatic ring as a substituent. Specifically, the phosphorus compound includes, for example, a phosphoric acid ester having a lower alkyl group having 2 or less carbon atoms as a substituent, such as trimethyl phosphate and triethyl phosphate [(OR) ₃ -P=O; R=number of carbon atoms 1 or 2 alkyl groups] is preferred.

The phosphorus compound is preferably used so that the concentration in the system is 50 ppm to 90 ppm, preferably 60 ppm to 80 ppm, more preferably 60 ppm to 75 ppm or less in terms of P element.

In a preferred embodiment of the esterification reaction step, before the esterification reaction is completed, a titanium chelate containing 1 ppm to 30 ppm of citric acid or citrate as a ligand in terms of Ti element is added to the dicarboxylic acid component and the diol component. After adding the complex, in the presence of the chelate titanium complex, add a magnesium salt of a weak acid of 60 ppm to 90 ppm (more preferably 70 ppm to 80 ppm) in terms of Mg element, and after the addition, further add 60 ppm in terms of P element. Examples include an embodiment in which a pentavalent phosphoric acid ester having no aromatic ring as a substituent is added in an amount of up to 80 ppm (more preferably 65 ppm to 75 ppm or less).

In the above embodiment, for each of the chelate titanium complex (organic chelate titanium complex), magnesium salt (magnesium compound), and pentavalent phosphate ester (phosphorus compound), 70% by mass or more of the total amount added is It is preferable that they be added in this order.

In addition, the esterification reaction in the esterification reaction step uses a multi-stage device in which at least two reaction vessels are connected in series, and the water or alcohol produced by the reaction is removed from the system under conditions where ethylene glycol is refluxed. It can be carried out while removing.
At this time, it is preferable that a slurry containing the dicarboxylic acid component and the diol component is prepared and continuously supplied to the reaction tank.

The esterification reaction in the esterification reaction step may be performed in one step or may be performed in multiple steps.
When the esterification reaction is carried out in one step, the esterification reaction temperature is preferably 230°C to 260°C, more preferably 240°C to 250°C.
When the esterification reaction is carried out in two stages, the temperature of the esterification reaction in the first reaction tank is 230°C to 260°C (more preferably 240°C to 250°C), and the pressure is 1.0 kg/cm. ² to 5.0 kg/cm ² (more preferably 2.0 kg/cm ² to 3.0 kg/cm ² ). Furthermore, the temperature of the esterification reaction in the second reaction tank is 230°C to 260°C (more preferably 245°C to 255°C), and the pressure is 0.5kg/cm ² to 5.0kg/cm ² (more preferably 245°C to 255°C). It is preferably 1.0 kg/cm ² to 3.0 kg/cm ² ).
When carrying out the esterification reaction in three or more stages, the conditions for the esterification reaction in the intermediate stage are preferably set to those between the first reaction tank and the final reaction tank.

- Polycondensation reaction step In the polycondensation reaction step, the esterification reaction product (oligomer, etc.) produced in the esterification reaction step is subjected to a polycondensation reaction to produce a polycondensate.
The polycondensation reaction may be carried out in one step or may be carried out in multiple steps. Among these, it is preferable to carry out the polycondensation reaction in multiple stages.

When the polycondensation reaction is carried out in three stages, for example, the conditions in each reaction tank are preferably as follows. The temperature of the first reaction tank is 255°C to 280°C (more preferably 265°C to 275°C), and the pressure is 100 to 10 torr: 13.3 × 10 ^-3 to 1.3 × 10 ^-3 MPa (more preferably 265 to 275 °C). It is preferably 50 torr to 20 torr: 6.67×10 ⁻³ MPa to 2.67×10 ⁻³ MPa). The second reaction tank has a temperature of 265° C. to 285° C. (more preferably 270° C. to 280° C.) and a pressure of 20 torr to 1 torr: 2.67×10 ⁻³ MPa to 1.33×10 ⁻⁴ MPa (more preferably 270° C. to 280° C.). It is preferably 10 torr to 3 torr (1.33×10 ⁻³ MPa to 4.0×10 ⁻⁴ MPa). The third reaction tank, which is the final reaction tank, has a temperature of 270°C to 290°C (more preferably 275°C to 285°C) and a pressure of 10 torr to 0.1 torr: 1.33×10 ⁻³ MPa to 1 .33×10 ⁻⁵ MPa (more preferably 5 torr to 0.5 torr: 6.67×10 ⁻⁴ MPa to 6.67×10 ⁻⁵ MPa).

A polyester resin is synthesized as described above. The synthesized polyester resin is used as a raw material for a polyester base material.
The synthesized polyester resin further contains additives such as light stabilizers, antioxidants, ultraviolet absorbers, flame retardants, lubricants (fine particles), nucleating agents (crystallizing agents), and crystallization inhibitors. You can.

-Solid phase polymerization step It is preferable that the polyester resin obtained through the above steps is further subjected to solid phase polymerization. By subjecting the polyester resin to solid phase polymerization, the water content, crystallinity, intrinsic viscosity (IV), etc. of the polyester base material can be controlled.

In the solid phase polymerization process, pelletized polyester resin is used.
The solid phase polymerization of polyester resin may be carried out by a continuous method (a tower is filled with resin, the tower is heated and allowed to flow slowly for a predetermined period of time, and then sequentially sent out) or a batch method (a tower is filled with resin and the resin is poured into a container) may also be used.
Solid phase polymerization is preferably carried out in vacuum or under a nitrogen atmosphere.
The solid state polymerization temperature of the polyester resin is preferably 150°C to 250°C, more preferably 170°C to 240°C, even more preferably 180°C to 230°C.
Further, the solid phase polymerization time is preferably 1 hour to 100 hours, more preferably 5 hours to 100 hours, even more preferably 5 hours to 75 hours, particularly preferably 5 hours to 30 hours. When the solid phase polymerization time is within the above range, the intrinsic viscosity (IV) can be easily controlled within a preferred range.

[Stretching process]
The stretching process includes a first stretching process in which an unstretched polyester film is stretched in either the transport direction or the width direction to form a uniaxially stretched polyester film, and a uniaxially stretched polyester film is stretched in either the transport direction or the width direction. This is a step in which a second stretching step of forming a biaxially stretched polyester film by stretching in the other direction is carried out stepwise or simultaneously.
One of the first stretching process and the second stretching process is a longitudinal stretching process in which the polyester film is stretched in the transport direction (hereinafter also referred to as "longitudinal stretching"), and the other of the first stretching process and the second stretching process is This is a transverse stretching step in which the polyester film is stretched in the width direction (hereinafter also referred to as "lateral stretching"). During stretching, polyester polymers are aligned in each direction.

The stretching step 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 stages. Examples of the sequential biaxial stretching include, for example, an embodiment in which longitudinal stretching is performed in the order of transverse stretching; an embodiment in which longitudinal stretching is performed in the order of longitudinal stretching, lateral stretching, and longitudinal stretching; and an embodiment in which longitudinal stretching is performed in the order of longitudinal stretching, longitudinal stretching, and transverse stretching. It will be done. Among these, it is preferable that the sequential biaxial stretching is carried out in the order of longitudinal stretching and transverse stretching.
Hereinafter, an embodiment in which longitudinal stretching and transverse stretching are performed in this order will be described, but the above manufacturing method is not limited to this embodiment.

The stretching ratio in the longitudinal stretching step is appropriately set, but preferably 2.0 times to 5.0 times, more preferably 2.5 times to 4.0 times, and still more preferably 2.8 times to 4.0 times. preferable.
The stretching speed in the longitudinal stretching step is preferably 800%/sec to 1500%/sec, more preferably 1000%/sec to 1400%/sec, and even more preferably 1200%/sec to 1400%/sec. Here, "stretching speed" is the value obtained by dividing the length Δd in the transport direction of the polyester film stretched per second in the longitudinal stretching process by the length d0 in the transport direction of the polyester film before stretching, as a percentage. This is the value expressed as .
In the longitudinal stretching step, it is preferable to heat the unstretched polyester film. This is because heating facilitates longitudinal stretching.

In the transverse stretching process, it is preferable to preheat the uniaxially stretched polyester film before the transverse stretching (also referred to as a preheating process). By preheating the uniaxially stretched polyester base material, the uniaxially stretched polyester base material can be easily laterally stretched.
The stretching ratio in the width direction of the uniaxially stretched polyester film in the lateral stretching step (lateral stretching ratio) is not particularly limited, but it is preferably larger than the stretching ratio in the longitudinal stretching step.
The stretching ratio in the transverse stretching step is preferably 3.0 times to 6.0 times, more preferably 3.5 times to 5.0 times, even more preferably 3.5 times to 4.5 times.
The stretching speed in the transverse stretching step is preferably 8%/sec to 45%/sec, more preferably 10%/sec to 30%/sec, even more preferably 15%/sec to 20%/sec.

[Particle-containing layer formation process]
The particle-containing layer forming step is a step of applying a particle-containing layer-forming composition to one surface of a polyester film to form a particle-containing layer.
The particle-containing layer forming step is performed, for example, between the extrusion molding step and the first stretching step, between the first stretching step and the second stretching step, or after the stretching step. Among these, the particle-containing layer forming step is preferably carried out between the first stretching step and the second stretching step.
The particle-containing layer obtained by the particle-containing layer forming step has the same meaning as the layer explained in the section of the particle-containing layer above.
Hereinafter, a mode of applying the particle-containing layer-forming composition will be described.

First, the composition for forming a particle-containing layer will be explained.
The composition for forming a particle-containing layer can be prepared by mixing the components described in the section of the particle-containing layer above and a solvent.
Examples of the solvent include water and alcohol.

The composition for forming a particle-containing layer may contain one type of solvent alone, or may contain two or more types of solvents.
The content of the solvent is preferably 80% by mass to 99.5% by mass, more preferably 90% by mass to 99% by mass, based on the total mass of the particle-containing layer-forming composition.
That is, in the composition for forming a particle-containing layer, the total content of components (solid content) other than the solvent is preferably 0.5% by mass to 20% by mass with respect to the total mass of the composition for forming a particle-containing layer. , more preferably 1% by mass to 10% by mass.

Regarding each component other than the solvent in the composition for forming a particle-containing layer, the content of each component relative to the total mass of the solid content of the composition for forming a particle-containing layer is the preferable content of each component relative to the total mass of the above-mentioned particle-containing layer. It is preferable to adjust the content of each component in the composition for forming a particle-containing layer so that the content is the same as the content.

Moreover, the composition for forming a particle-containing layer may contain a crosslinking agent.
The crosslinking agent is not particularly limited, and any known crosslinking agent can be used. Examples of the crosslinking agent include melamine compounds, epoxy compounds, isocyanate compounds, carbodiimide compounds, and oxazoline compounds.
For details on the melamine compound, epoxy compound, and isocyanate compound, the descriptions in [0081] to [0083] of JP 2015-163457A can be referred to.
As for the carbodiimide compound, the descriptions in [0038] to [0040] of JP-A-2017-087421 can be referred to.
Regarding carbodiimide compounds and isocyanate compounds, the descriptions in [0074] to [0075] of International Publication No. 2018/034294 can be referred to.
Regarding the oxazoline compound, reference can be made to the descriptions in [0111] to [0117] of JP-A No. 2013-058746 and [0038] to [0048] of JP-A No. 2015-160434.
As for the crosslinking agent, the descriptions in [0082] to [0084] of International Publication No. 2017/169844 can also be referred to.

The content of the crosslinking agent is preferably 0% by mass to 50% by mass based on the total mass of the particle-containing layer.
In the composition for forming a particle-containing layer, the mass ratio of the crosslinking agent to the binder is preferably 2% by mass to 50% by mass.

The method for applying the particle-containing layer-forming composition is not particularly limited, and any known method can be used. Examples of the application method include spray coating, slit coating, roll coating, blade coating, spin coating, bar coating, and dip coating.

The heating temperature in forming the particle-containing 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.

In addition, in order to improve the adhesion between the polyester film and the particle-containing layer, the surface of the polyester film is subjected to pre-treatments such as anchor coating, corona treatment, and plasma treatment before forming the particle-containing layer. You can.

[Peeling layer formation process]
The release layer forming step is a step of applying a release layer forming composition to one side of a polyester film to form a release layer.
The release layer forming step is performed between the extrusion molding step and the first stretching step, between the first stretching step and the second stretching step, or after the stretching step.

Among them, from the viewpoint of producing a release film with reduced thickness unevenness, the release layer forming step is carried out between the extrusion molding step and the first stretching step, or between the first stretching step and the second stretching step. It is preferable that
That is, the release layer forming step is preferably a step of applying a release layer forming composition to one side of an unstretched polyester film or a uniaxially stretched polyester film to form a release layer. By performing the release layer forming step at the above timing, the heating time of the polyester film in the manufacturing process is shortened, and the influence of heat history can be reduced, so it is possible to suppress the streak-like wrinkles of the release film. As a result, the thickness unevenness of the ceramic green sheet can be reduced.

When the release layer forming step is performed after the stretching step, it is preferably performed after the cooling step described below, and more preferably after the winding step and trimming step described below.
The release layer formed in the release layer forming step has the same meaning as the layer explained in the section of the release layer above.

First, the composition for forming a release layer will be explained.
The composition for forming a release layer preferably contains the components described in the section for the release layer above and a solvent.
Examples of the solvent include water, alcohol, ether, ketone, and aromatic hydrocarbon.

The release layer forming composition may contain one type of solvent alone, or may contain two or more types of 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 composition for forming a release layer.
That is, in the composition for forming a release layer, the total content of components (solid content) other than the solvent is preferably 0.5% by mass to 20% by mass, and 1% by mass based on the total mass of the composition for forming a release layer. More preferably, the amount is from % by mass to 10% by mass.

Regarding each component other than the solvent in the composition for forming a release layer, the content of each component relative to the total mass of the solid content of the composition for forming a release layer is the preferred content of each component relative to the total mass of the release layer described above. It is preferable to adjust the content of each component in the composition for forming a peeling layer so that they are the same.

The method for applying the composition for forming a release layer is not particularly limited, and any known method can be used. A specific example of the application method is as described in the particle-containing layer forming step.

The heating temperature in 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.

In addition, in order to improve the adhesion between the polyester film and the release layer, the surface of the polyester film may be subjected to pretreatment such as anchor coating, corona treatment, or plasma treatment before providing the release layer. good.

[Heat setting process]
The method for producing a release film of the present disclosure may include a heat setting step after the stretching step as a heat treatment for the polyester film obtained in the stretching step.
In the heat-setting step, the polyester film stretched in the stretching step is heated and heat-set. By crystallizing the polyester resin through heat fixation, shrinkage of the polyester base material can be suppressed.

The heat setting step is preferably a step of heating a polyester film having a film width of 1 m or more. In this heat setting step, the maximum film surface temperature of the polyester film is controlled within the range of 160°C or more and 225°C or less, and the variation in the maximum film surface temperature in the film width direction is controlled to be 5.0°C or less. It is preferable to do so.
Note that the maximum film surface temperature is the maximum temperature reached on the surface of the polyester film during heat setting, and is also called heat setting temperature. The maximum film surface temperature can be measured with a radiation thermometer. The highest film surface temperature of a polyester film refers to the surface temperature at the center of the film in the width direction. In addition, the variation in the maximum film surface temperature in the film width direction can be determined by measuring the surface temperature at a total of three points in the film width direction, one point in the center and two points on both ends. It is calculated by subtracting the surface temperature of the smaller value.
In addition, by measuring the maximum temperature reached on the surface of the polyester film during heat setting using the method described above, measuring whether the desired temperature has been reached, and adjusting the heating conditions, the maximum temperature reached on the surface of the polyester film can be measured. Surface temperature can be controlled.
When the maximum film surface temperature is controlled to 160°C to 225°C as described above, the pre-peak temperature measured by DSC of the release film can be set to 160°C to 225°C. Further, by setting the variation in the maximum film surface temperature in the film width direction to 0.5° C. or less, the variation in crystallinity in the film width direction of the release film can be made to be 5.0% or less.
The variation in the maximum film surface temperature in the film width direction is more preferably 3.0°C or less, even more preferably 2.0°C or less, and particularly preferably 1.5°C or less.

Further, the polyester film may be heated only from one side of the polyester film during heat fixing, or may be heated from both sides of the polyester film. For example, when the melt is cooled on a casting drum during an extrusion molding process, one side of the formed polyester film is cooled differently than the other side, making the film susceptible to curling. ing. Therefore, it is preferable that heating in the heat setting step be performed on the surface that was brought into contact with the casting drum in the extrusion molding step. Curling can be eliminated by using the heating surface in the heat-setting step as the surface in contact with the casting drum, that is, the cooling surface.
At this time, the heating is such that the surface temperature immediately after heating on the heated surface in the heat fixing step is higher in the range of 0.5 to 5.0 degrees Celsius than the surface temperature of the non-heated surface on the opposite side to the heated surface. It is preferable to do so. When the temperature of the heated surface during heat setting is higher than that of the opposite surface, and the temperature difference between the front and back surfaces is 0.5° C. to 5.0° C., curling of the film can be more effectively eliminated. From the viewpoint of the curl eliminating effect, the temperature difference between the heated surface and the non-heated surface on the opposite side is more preferably 0.7°C to 3.0°C, and 0.8°C to 2.0°C. More preferred.

At the ends of the polyester film in the width direction perpendicular to the longitudinal direction, the temperature tends to drop because clips or the like are attached during stretching, which tends to cause temperature variations in the width direction, and thus variations in the degree of crystallinity. Therefore, it is preferable to heat the ends of the polyester film in the width direction during heat setting. In particular, it is more preferable to radiantly heat the ends of the polyester film in the width direction during heat setting using a radiant heater such as an infrared heater. When radiant heating is performed, it is preferable to narrow the temperature variation in the width direction of the film to within 3.0°C. Thereby, the variation in crystallinity in the film width direction can be made 5.0% or less, preferably 3.0% or less.

In addition to the heat setting process, the polyester film is further configured to radiately heat the widthwise end portions of the polyester film with a radiant heater such as an infrared heater in at least one of the preheating process, stretching process, and thermal relaxation process. Good too. Heating to the ends in the width direction reduces temperature variations in the width direction and ultimately variations in crystallinity, and is applied not only during heat setting but also during preheating, stretching, and thermal relaxation. A higher improvement effect can be expected by further heating in the step.

As mentioned above, the heat setting temperature in the heat setting step, that is, the highest film surface temperature of the polyester film is preferably 160°C to 225°C, more preferably 160°C to 220°C, and 180°C. More preferably, the temperature is between 210°C and 210°C.
The heating time in the heat-setting step, that is, the residence time in the heat-setting section, is preferably from 5 seconds to 50 seconds, more preferably from 8 seconds to 40 seconds, and even more preferably from 10 seconds to 30 seconds. Here, the residence time is the time during which the polyester film continues to be heated within the heat fixing section.

[Thermal relaxation process]
The method for manufacturing a release film of the present disclosure preferably includes a heat relaxation step after the heat setting step.
In the thermal relaxation step, it is preferable to thermally relax the polyester film heat-set in the heat-setting step by heating it at a temperature lower than that in the heat-setting step. Residual strain in polyester film can be alleviated by thermal relaxation.
The surface temperature (thermal relaxation temperature) of the polyester film in the heat 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 or more. Low temperatures are particularly preferred. That is, the thermal relaxation temperature is preferably 235°C or lower, more preferably 225°C or lower, even 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 method for producing a release film of the present disclosure preferably includes a cooling step of cooling the polyester film that has been thermally relaxed in the thermal relaxation step.
In addition, by adjusting the cooling rate when cooling the heat-relaxed polyester film after the heat-setting step, it becomes easier to suppress the streak-like wrinkles that occur on the surface of the release layer of the release film (i.e., the release surface). . By suppressing streak-like wrinkles that occur on the surface of the release layer of a release film, it is possible to suppress uneven thickness of ceramic green sheets produced using such a release film.

Examples of methods for cooling the polyester film in the cooling step include a method of applying wind (preferably cold air) to the polyester film, and a method of bringing the polyester film into contact with a temperature-adjustable member (e.g., a temperature control roll). .

The cooling rate of the polyester film in the cooling step is preferably 500°C/min to 4000°C/min, more preferably 700°C/min to 3000°C/min, and even more preferably 1000°C/min to 2500°C/min. Within the above range, it becomes easy to suppress the streak-like wrinkles that occur on the surface of the release layer of the release film, and it is possible to produce a ceramic green sheet with suppressed thickness unevenness.

The cooling rate of the polyester film in the cooling process can be measured using a non-contact thermometer. For example, first, the surface temperature of the polyester film at the start of the cooling process and the surface temperature of the polyester film at the end of the cooling process are measured to obtain the temperature difference ΔT (° C.) between the two. The cooling rate is determined by dividing the obtained temperature difference ΔT (° C.) by the cooling process time ta.
The start of the cooling process refers to the time when the above-mentioned cooling method begins to be applied to the polyester film being transported, and the end of the cooling process refers to the time when the application of the above-mentioned cooling method to the polyester film ends. Point. The cooling process time corresponds to the time from the start of the cooling process to the end of the cooling process.
In addition, the cooling rate of the polyester film can be adjusted by various conditions in the above-mentioned cooling method and the transport speed of the polyester film.

In addition, in the method for manufacturing a release film of the present disclosure, it is preferable that the above-mentioned heat setting step, heat relaxation step, and cooling step are performed continuously in this order. This reduces the load (thermal history) caused by repeated heating and cooling on the polyester film, reduces the distortion inherent in the polyester film, and suppresses the above-mentioned streak-like wrinkles in the release film. be.

In the cooling step, it is also preferable to include a step of expanding the thermally relaxed polyester film in the width direction (expansion step). By including the expansion step, it becomes easier to suppress the above-mentioned streak-like wrinkles in the release film.
The expansion rate in the width direction of the polyester film in the expansion step, that is, the ratio of the polyester film width at the end of the cooling step to the polyester film width before the start of the cooling step, is preferably 0% or more, and more preferably 0.001% or more. It is preferably 0.01% or more, and more preferably 0.01% or more.
The upper limit of the expansion rate is not particularly limited, but is preferably 1.3% or less, more preferably 1.2% or less, and even more preferably 1.0% or less.

[Winding process]
The method for producing a release film of the present disclosure may include a winding step of obtaining a roll-shaped polyester film by winding up the polyester film obtained through the above steps.

[Trimming process]
The manufacturing method of the present disclosure includes a trimming step of continuously cutting the polyester film along the transport direction and cutting off at least one end in the width direction of the polyester film, before implementing the winding step. You can stay there.

[Other conditions]
The conveyance speed of the polyester film in each step other than the longitudinal stretching step of the method for producing a release film of the present disclosure is not particularly limited, but in the lateral stretching step, heat setting step, heat relaxation step, and cooling step, productivity and In terms of quality, the speed is preferably 50 m/min to 200 m/min, more preferably 80 m/min to 150 m/min.

In addition, in the method for producing a release film of the present disclosure, a method has been described in which a composition for forming a particle-containing layer is applied in the particle-containing layer forming step to form a particle-containing layer, but the method for forming a particle-containing layer is the same as described above. The method is not limited to the embodiment, and any known method can be used. For example, a method of forming an unstretched polyester film on which particle-containing layers are laminated by coextrusion molding may be mentioned.

In particular, the method for manufacturing a release film of the present disclosure includes:
A longitudinal stretching step of stretching an unstretched polyester film in the transport direction;
A step of applying a particle-containing layer forming composition to one side of the uniaxially stretched polyester film obtained in the longitudinal stretching step to form a particle-containing layer;
A step of applying a release layer forming composition to the other surface of the uniaxially stretched polyester film obtained in the longitudinal stretching step to form a release layer;
It is preferable to include a transverse stretching step of stretching a uniaxially stretched polyester film having a particle-containing layer and a release layer in the width direction while heating it.

[Laminated body]
The laminate of the present disclosure includes the above-described release film of the present disclosure and a layer containing ceramic.

Details of the release film are as described above.
The ceramic-containing layer may be provided directly on the surface of the release film or may be provided on the release film via another layer, but it is preferable to provide it directly on the surface of the release film because smoothness is better. is preferred.

The ceramic included in the ceramic-containing layer is not particularly limited as long as it is included in the ceramic green sheet, and examples include ferroelectric materials such as barium titanate, and paraelectric materials such as titanium oxide and calcium titanate. Examples include materials.

Preferably, the ceramic-containing layer includes a binder. The binder is not particularly limited as long as it is included in the ceramic green sheet, and examples thereof include polyvinyl butyral.

The laminate of the present disclosure can be manufactured, for example, by applying a ceramic slurry containing a ceramic and a solvent onto the release surface of a release film and drying the solvent contained in the ceramic slurry. Examples of the solvent include ethanol and toluene.

The method for applying the ceramic slurry is not particularly limited, and for example, known methods such as a reverse roll method can be applied.

Note that a ceramic green sheet can be obtained by peeling off the release film from the laminate of the present disclosure. That is, the layer containing ceramic powder in the laminate of the present disclosure becomes a ceramic green sheet.

The present disclosure will be explained in more detail by giving examples below. The materials, amounts used, proportions, processing details, and processing procedures shown in the following examples can be changed as appropriate without departing from the spirit of the present disclosure. Therefore, the scope of the present disclosure is not limited to the specific examples shown below.

<Preparation of polyester resin>
(Synthesis of polyester resin PET-1)
As shown below, a polyester resin is obtained using a continuous polymerization device using a direct esterification method in which terephthalic acid and ethylene glycol are directly reacted, water is distilled off, esterified, and then polycondensation is performed under reduced pressure. Ta.

(1) Esterification reaction In the first esterification reaction tank, 4.7 tons of high-purity terephthalic acid and 1.8 tons of ethylene glycol were mixed over 90 minutes to form a slurry, and the mixture was continuously mixed at a flow rate of 3800 kg/h. It was supplied to the first esterification reactor. Furthermore, an ethylene glycol solution of a citric acid chelate titanium complex (VERTEC AC-420, manufactured by Johnson Matthey) in which citric acid is coordinated to Ti metal was continuously supplied, and the temperature inside the reaction tank was 250°C, with stirring, and the average residence time was increased. The reaction took about 4.3 hours. At this time, the citric acid chelate titanium complex was continuously added so that the amount of Ti added was 9 ppm in terms of elemental value. At this time, the acid value of the obtained oligomer was 600 equivalents/ton. In addition, in this specification, "equivalent/t" represents the molar equivalent per ton.

This reactant was transferred to a second esterification reactor and reacted with stirring at an internal temperature of 250° C. for an average residence time of 1.2 hours to obtain an oligomer with an acid value of 200 equivalents/ton. The second esterification reaction tank is internally partitioned into three zones, and an ethylene glycol solution of magnesium acetate is continuously supplied from the second zone so that the amount of Mg added becomes 75 ppm in terms of elemental value. An ethylene glycol solution of trimethyl phosphate was continuously supplied from the third zone so that the amount of P added was 65 ppm in elemental terms.

(2) Polycondensation reaction The esterification reaction product obtained above was continuously supplied to the first polycondensation reaction tank, and under stirring, the reaction temperature was 270°C, and the reaction tank internal pressure was 20 torr (2.67×10 ^{− 3} MPa) with an average residence time of about 1.8 hours.

Furthermore, the mixture was transferred to a second double condensation reaction tank, where it was stirred for a residence time of about 1.2 hours at a reaction tank temperature of 276°C and a reaction tank pressure of 5 torr (6.67×10 ^-4 MPa). The reaction (polycondensation) was carried out under the following conditions.

Next, it was further transferred to a third polycondensation reaction tank, where the reaction tank temperature was 278°C, the reaction tank pressure was 1.5 torr (2.0 x 10 ^-4 MPa), and the residence time was 1.5 hours. A reaction (polycondensation) was carried out under the following conditions to obtain a reactant (polyethylene terephthalate (PET)).

Next, the obtained reaction product was discharged into cold water in the form of a strand, and immediately cut to produce polyester resin pellets <cross section: major axis approximately 4 mm, minor axis approximately 2 mm, length: approximately 3 mm>.

The obtained polyester resin was measured using high-resolution high-frequency inductively coupled plasma-mass spectrometry (HR-ICP-MS; AttoM manufactured by SII Nanotechnology) as shown below. As a result, Ti = 9 ppm, Mg = 75 ppm. , P=60 ppm. P was slightly reduced compared to the initial amount added, but it is presumed that it was volatilized during the polymerization process.

(3) Solid phase polymerization reaction The polyester resin pellets obtained as described above were subjected to solid phase polymerization by a batch method. That is, after putting polyester resin pellets into a container, preliminary crystallization was performed at 150° C. while stirring under vacuum, and then a solid phase polymerization reaction was performed at 190° C. for 7 hours.
In the manner described above, polyester resin PET-1 was obtained.

(Polyester resin PET-2 to PET-4)
In the synthesis of polyester resin PET-1, the same procedure was followed except that the solid phase polymerization time was changed from 7 hours to 12 hours (P-2), 9 hours (P-3), or 0 hours (P-4). , polyester resins PET-2 to PET-4 were obtained, respectively.

(Polyester resin PET-5)
An ethylene glycol solution of silica particles was added to the polyester resin PET-1 obtained in the synthesis of the polyester resin PET-1 so that the content was 1% by mass with respect to the polyester resin PET-1. Got 5.

<Example 1>
(Extrusion molding process)
After drying the polyester resin PET-1 to a moisture content of 20 ppm or less, it was charged into a hopper of a single-screw extruder having a diameter of 50 mm. Polyester resin PET-1 was melted at 300° C. and extruded from a die through a gear pump and a filter (pore diameter: 20 μm) under the following extrusion conditions.
At this time, extrusion of the molten resin was carried out under conditions of a pressure fluctuation of 1% and a temperature distribution of the molten resin of 2%. Specifically, the back pressure in the barrel of the extruder is set to be 1% higher than the average pressure inside the barrel of the extruder, and the piping temperature of the extruder is set to be 2% higher than the average temperature inside the barrel of the extruder. Heated as temperature. When extruding from the die, the molten resin was extruded onto a cooling cast drum and brought into close contact with the cast drum using an electrostatic application method. The molten resin was cooled by setting the temperature of the casting drum to 25°C and blowing cold air at 25°C from a cold air generator installed facing the casting drum. The unstretched polyester film (unstretched polyester film 1) was peeled off using a peeling roll placed opposite to the cast drum.

(Longitudinal stretching process)
The unstretched polyester film 1 was passed between two pairs of nip rolls having different circumferential speeds and stretched in the longitudinal direction (conveyance direction) under the following conditions to produce a uniaxially stretched polyester film (longitudinal stretched polyester film 1).
Preheating temperature: 80℃
Longitudinal stretching temperature: 90℃
Longitudinal stretching ratio: 3.6 times Longitudinal stretching stress: 12 MPa

(Particle-containing layer formation process, peeling layer formation process)
A particle-containing layer forming composition A1 shown below was applied to one side of a polyester film uniaxially stretched in the longitudinal direction (longitudinal stretched polyester film 1) using a bar coater. A release layer forming composition L1 shown below was applied using a bar coater to the surface of the uniaxially stretched polyester film opposite to the surface on which the particle-containing layer was applied. The formed coating film was dried with hot air at 100° C. to form a particle-containing layer and a release layer. That is, the composition A1 for forming a particle-containing layer and the composition L1 for forming a release layer were applied in-line to a uniaxially stretched polyester film. At this time, the particle-containing layer forming composition A1 and the releasing layer forming composition L1 were mixed so that the particle-containing layer had a thickness of 60 nm and the release layer had a thickness of 60 nm after lateral stretching, which will be described later. The amount of application was adjusted.

[Preparation of particle-containing layer forming composition A1]
Particle-containing mixed liquid A was prepared by mixing each component shown below. The prepared particle-containing mixture A was subjected to filtration treatment using a filter (F20, manufactured by MAHLE Filter Systems Co., Ltd.) with a pore size of 6 μm, and membrane degassing (2 × 6 radial flow Super Phobic, Polypore Co., Ltd.) was carried out to obtain particle-containing layer forming composition A1.
・Organic particle A (MP1000, manufactured by Soken Kagaku Co., Ltd., non-crosslinked acrylic particles, solid content 100% by mass): 8 parts by mass ・Organic particle B (Nipol (registered trademark) UFN1008, manufactured by Nippon Zeon Co., Ltd., polystyrene water Dispersion liquid, solid content 20% by mass): 8 parts by mass Acrylic resin (polymerized with methyl methacrylate, styrene, 2-ethylhexyl acrylate, 2-hydroxyethyl methacrylate and acrylic acid at a mass ratio of 59:8:26:5:2) Aqueous dispersion of a copolymer obtained by making a copolymer, solid content concentration 25% by mass): 141 parts by mass, urethane resin (Superflex (registered trademark) 210, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., ester-based urethane aqueous dispersion, Solid content concentration 35% by mass): 38 parts by mass Anionic hydrocarbon surfactant (Rapizole (registered trademark) A-90, di-2-ethylhexyl sodium sulfosuccinate, manufactured by NOF Corporation, solid content concentration 1 Mass% water diluted solution): 12 parts by mass, carbodiimide crosslinking agent (Carbodilite (registered trademark) V-02-L2, manufactured by Nisshinbo Co., Ltd., an aqueous crosslinking agent in which a hydrophilic segment is added to a polycarbodiimide resin, solid (concentration 40% by mass): 20 parts by mass, benzyl alcohol: 4 parts by mass, water: 769 parts by mass

[Preparation of composition L1 for forming a peeling layer]
A mixed liquid L was prepared by mixing each component shown below. The prepared mixture L was subjected to the same filtration treatment and membrane degassing as in the composition A1 for forming a particle-containing layer, to obtain a composition L1 for forming a peeling layer.
- Silicone emulsion (DEHESIVE (registered trademark) EM 480 JP, manufactured by Asahi Kasei Wacker Silicone Co., Ltd.): 200 parts by mass - Silicone emulsion (CROSSLINKER V72, manufactured by Asahi Kasei Wacker Silicone Co., Ltd.): 30 parts by mass - Silane coupling agent ( KBM-403, manufactured by Shin-Etsu Chemical Co., Ltd.): 1 part by mass, water: 770 parts by mass

(lateral stretching process)
A longitudinally stretched polyester film 1 (longitudinal stretched polyester film 1) provided with a particle-containing layer and a release layer is subjected to transverse stretching by applying tension in the film width direction perpendicular to the longitudinally stretched direction (longitudinal direction) under the following conditions. did.
<Condition>
・Preheating temperature: 110℃
・Stretching temperature (lateral stretching temperature): 120℃
・Stretching ratio (lateral stretching ratio): 4.4 times ・Stretching stress (lateral stretching stress): 18 MPa

(Heat fixation process)
Next, while controlling the maximum membrane surface temperature of the polyester film within the following range, finely adjust the speed of the hot air coming out of the hot air blowing nozzle so that the variation in the maximum membrane surface temperature in the width direction falls within the following range. It was heated and crystallized (heat setting step). At this time, both ends of the film in the width direction were radiantly heated with an infrared heater (heater surface temperature: 450° C.) from the cast surface side that came into contact with the cast drum during the film forming process.
・Maximum film surface temperature (heat setting temperature: T _{heat setting} ): Temperature shown in Table 1 below [℃]
・Variations in the highest film surface temperature (heat setting temperature: T _{heat setting} ) in the film width direction: Temperatures shown in Table 1 below [°C]
Note that the above T _{heat setting} (maximum film surface temperature) and the variation in T _{heat setting} in the film width direction are values measured by the method described above.

(Thermal relaxation process)
The polyester film after heat setting was heated to the temperature shown below to relieve the tension of the film. At this time, both ends of the film in the width direction were radiantly heated from the cast surface side using an infrared heater (heater surface temperature: 350° C.), similarly to the heat fixing step.
・Thermal relaxation temperature (T _{thermal relaxation} ): 150℃
・Thermal relaxation rate: TD direction (film width direction) = 5%
MD direction (direction perpendicular to the film width direction) = 5%

(cooling process)
Next, the polyester film after thermal relaxation was cooled to 70°C at a cooling rate of 1500°C/min.

(Film collection)
After cooling, both ends of the polyester film were trimmed by 20 cm. Thereafter, both ends were subjected to extrusion processing (knurling) to a width of 10 mm, and then wound up at a tension of 25 kg/m.

As described above, a release film having a width of 1.5 m, a length of 7000 m, and a thickness of 31 μm was produced.
In the release film, the thickness of the polyester base material was 517 times the thickness of the release layer.

<Example 2 to Example 9, Example 12 to Example 14>
A release film was produced in the same manner as in Example 1, except that the manufacturing process of the release film and the physical properties of the release film were appropriately changed as shown in Table 1.
Particle-containing layers containing the resins listed in Table 1 were formed by changing the type of resin (that is, binder) in composition A1 for forming particle-containing layers.

<Example 10>
A biaxially stretched film containing a particle-containing layer and a polyester base material was produced in the same manner as in Example 7, except that a release layer was not formed. The obtained film was unrolled, and the following release layer forming composition L2 was applied to the surface of the polyester base opposite to the particle-containing layer so that the thickness after curing was 60 nm. After drying the formed coating film at 90° C., it was thermally cured by heating at 120° C. for 1 minute to form a release layer, thereby producing a release film.

[Preparation of composition L2 for forming a peeling layer]
A mixed liquid L was prepared by mixing each component shown below. The prepared mixed solution L was subjected to the same filtration treatment and membrane degassing as for the composition A1 for forming a particle-containing layer, to obtain a composition L2 for forming a peeling layer.
・Acrylic resin (copolymer made by polymerizing methyl methacrylate, stearyl methacrylate, 2-hydroxyethyl methacrylate, and methacrylic acid at a mass ratio of 47:26:20:7, solid content 40% by mass toluene solution): 1.75 Part by mass: Polyester-modified silicone resin (BYK-370, manufactured by BYK Chemie Japan Co., Ltd., solid content concentration 25% by mass): 0.05 part by mass - Thermopolymerizable compound (hexamethoxymethylmelamine, Tokyo Kasei Kogyo Co., Ltd.) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., solid content 10% by mass): 0.25 parts by mass / Acid catalyst (p-toluenesulfonic acid, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., solids content 100% by mass): 0.02 parts by mass / Methyl ethyl ketone: 58 Parts by mass/Toluene: 40 parts by mass

<Example 11>
A release film was produced in the same manner as in Example 10, except that in the extrusion molding process, an unstretched film was produced by coextruding polyester resin PET-1 and polyester resin PET-5.

<Comparative example 1>
The polyester resins used for coextrusion were changed to polyester resin PET-3 and polyester resin PET-5, the heat setting temperature was changed to T _{heat setting} , radiant heating with an infrared heater was not performed, and the release film was A release film was produced in the same manner as in Example 11 except that the thickness was changed.

<Comparative example 2>
A release film was prepared in the same manner as in Example 10, except that polyester resin PET-1 was changed to polyester resin PET-4, heat setting temperature: T was changed, and radiant _heating with an infrared heater was not performed. was created.

<Comparative example 3>
Example 7 except that in the extrusion molding process, an unstretched film was produced by co-extruding polyester resin PET-4 and polyester resin PET-5, and that the heat setting temperature: T _{heat setting} was changed. A release film was prepared in the same manner as above.

<Comparative example 4>
The polyester resins used for coextrusion were changed to polyester resin PET-1 and polyester resin PET-5, the heat setting temperature was changed to T _{heat setting} , radiant heating with an infrared heater was not performed, and the release film was A release film was produced in the same manner as Comparative Example 3 except that the thickness was changed.

Details of each component listed in Table 1 are as follows.
Note that PET-1 to PET-5 are the above-mentioned polyester resin PET-1 to polyester resin PET-5.

(resin)
・Acrylic: Acrylic resin (copolymer made by polymerizing methyl methacrylate, styrene, 2-ethylhexyl acrylate, 2-hydroxyethyl methacrylate, and acrylic acid at a mass ratio of 59:8:26:5:2 ・Urethane: Urethane resin (Superflex (registered trademark) 210, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., ester-based urethane aqueous dispersion)
・Olefin: Olefin resin (Zaixen NC, manufactured by Sumitomo Seika Co., Ltd.)

<Measurement>
The following various measurements were performed using the produced release film. The measurement results are shown in Table 1 below.

(1) Pre-peak temperature, intrinsic viscosity, and thickness of the release layer measured by DSC The pre-peak temperature, intrinsic viscosity, and thickness of the release layer measured by DSC of the release film were measured by the method described above. .

(2) Variation in Crystallinity A total of 3 points, 1 point in the center and 2 points at both ends, were cut out from the entire width of the release film at a width of 30 mm and a length of 120 mm to obtain 3 measurement samples. By measuring the crystallinity of the three measurement samples and subtracting the smaller crystallinity of the measurement samples at both ends from the crystallinity of the measurement sample at the center, The variation in crystallinity was calculated. At this time, the degree of crystallinity was calculated from the density of the film.
Specifically, using the density X (g/cm ³ ) of the film, the density Y (g/cm ³ ) at 0% crystallinity, and the density Z (g/cm ³ ) at 100% crystallinity. The degree of crystallinity Xc (%) was derived using the following calculation formula. Note that the density was measured according to JIS K 7112:1999.
Xc={Z×(X-Y)}/{X×(Z-Y)}×100

(3) Variation in heat shrinkage rate The release film was cut to obtain a sample piece M having a size of 30 mm in the width direction and 120 mm in the longitudinal direction. Two reference lines were placed on the sample piece M at a distance of 100 mm in the longitudinal direction, and the sample piece M was left in a heating oven at 150° C. for 30 minutes without tension. After standing, the sample piece M is cooled to room temperature, the distance between the two reference lines is measured, this value is set as Amm, "100 x (100-A)/100" is calculated, and the obtained value is calculated as the longitudinal direction. It was defined as the thermal shrinkage rate in the direction.
In addition, a sample piece L with a size of 30 mm in the longitudinal direction and 120 mm in the width direction was obtained, and two reference lines were inserted into this sample piece L at an interval of 100 mm in the width direction. Measurement and calculation were carried out using the following methods, and the obtained value was taken as the heat shrinkage rate in the width direction.
The above operation was performed using a sample that was cut out from three points in total, one point in the center and two points at both ends, from the entire width of the release film. The absolute value was obtained by subtracting the heat shrinkage ratio with a larger difference from the heat shrinkage ratio of the other parts, and the variation in the heat shrinkage ratio in each of the longitudinal direction (MD) and the width direction (TD) was determined.

(4) Measurement of thickness The thickness of the release film was measured at five different positions using a contact film thickness meter (manufactured by Anritsu Corporation). The arithmetic mean value of the obtained measured values was determined, and this was taken as the thickness of the release film.

Using the prepared release film, evaluations were made regarding local protrusions and thickness unevenness in the particle-containing layer, and unevenness defects in the ceramic green sheet. The evaluation method is as follows.

<Local protrusion>
The surface of the particle-containing layer of the prepared release film was measured using an optical interferometer (Vertscan 3300G Lite, manufactured by Hitachi High-Tech Corporation) under the following conditions, and then the built-in data analysis software (VS-Measure5 ) was analyzed.
Measurements were performed 100 times at different measurement positions, and the total number of protrusions with a height exceeding 50 nm was determined.
(Measurement condition)
・Measurement mode: WAVE mode ・Objective lens: 50x ・Measurement area: 186μm x 155μm

(Evaluation criteria)
A: The maximum protrusion height Sp is 800 nm or less, and the total number of protrusions exceeding 50 nm is 0 to 2. B: The maximum protrusion height Sp is 800 nm or less, and the total number of protrusions exceeds 50 nm. The total number of protrusions is 3 to 9. C: The maximum protrusion height Sp is over 800 nm, or the total number of protrusions with a height exceeding 50 nm is 10 or more.

<Uneven thickness>
(Preparation of black slurry)
A black slurry was prepared by mixing the components shown below and dispersing the mixture using a ball mill.
・Polyvinyl butyral (manufactured by Sekisui Chemical Co., Ltd., S-LEC BX-5): 5 parts by mass ・Resin-coated carbon black produced according to the description in paragraphs [0036] to [0042] of Patent No. 5320652: 10 parts by mass Mixed solvent of toluene and ethanol mass ratio 6:4: 45 parts by mass

While conveying the release film produced in each example and comparative example at 70 m/min, the above black slurry was applied onto the release layer using a slit-shaped nozzle so that the thickness after drying was 0.5 μm. After that, the coating film was dried under a temperature condition of 90° C. to form a black layer.
The release film provided with the black layer was placed on a light table, and the color unevenness of the black layer was visually observed at a position 1 m away from the release film, and evaluated according to the following evaluation criteria.

(Evaluation criteria)
A: No color unevenness in the black layer is observed.
B: Slight color unevenness in the black layer was observed.
C: Color unevenness in the black layer was clearly observed.
When no color unevenness of the black layer is confirmed, it means that the thickness of the black layer is uniform, that is, there is no thickness unevenness. Note that it is presumed that by using a release film that can form a black layer with no visible color unevenness, it is possible to suppress overall thickness unevenness of the ceramic green sheet.

<Uneven defects>
(Preparation of ceramic slurry)
100 parts by mass of barium titanate powder (BaTiO ₃ ; manufactured by Sakai Chemical Industry Co., Ltd., product name "BT-03") as a ceramic, polyvinyl butyral resin as a binder (product name "S-LEC (registered trademark) B・K BM") -2'', manufactured by Sekisui Chemical Co., Ltd.), 8 parts by weight, 4 parts by weight of dioctyl phthalate as a plasticizer (product name ``Dioctyl phthalate Shika 1 grade'', manufactured by Kanto Chemical Co., Ltd.), and toluene and 135 parts by mass of an ethanol mixture (mass ratio 6:4) was mixed. A ceramic slurry was obtained by dispersing the mixture using a ball mill in the presence of zirconia beads and removing the beads from the resulting dispersion.

The release films obtained in each Example and each Comparative Example were cut to a width of 250 mm and a length of 10 m. The cut release film was kept at room temperature and humidity (23° C., 50% RH) for 12 months. After storage, the following ceramic slurry was applied to the entire surface of the release film using a die coater so that the film thickness after drying was 1 μm. Thereafter, the obtained coating film was dried in a dryer at 100°C for 2 minutes. Thereby, a laminate including a release film and a ceramic-containing layer was obtained. Since the ceramic-containing layer becomes a ceramic green sheet after the release film is peeled off from the laminate, the laminate is hereinafter referred to as a release film with a ceramic green sheet.
The release film with the ceramic green sheet was once wound up into a roll. Thereafter, a fluorescent lamp was illuminated from the release film side of the unwound release film with ceramic green sheet, and a 1 m ² area on the surface of the ceramic green sheet was visually observed to check for uneven defects such as pinholes. The unevenness defects were evaluated based on the number of confirmed unevenness defects. The evaluation criteria are as follows.

(Evaluation criteria)
A: No unevenness defects were observed on the ceramic green sheet.
B: One to nine uneven defects were confirmed on the ceramic green sheet.
C: Ten or more uneven defects were confirmed on the ceramic green sheet.

The evaluation results are shown in Table 1.
In Table 1, if the formation method of the particle-containing layer is described as "in-line", it means that the particle-containing layer forming step was performed between the longitudinal stretching step and the horizontal stretching step, as in Example 1 above. means. If the method for forming the particle-containing layer is described as "coextrusion," it means that the unstretched polyester film and the particle-containing layer were formed by coextrusion during the extrusion molding process.
Furthermore, if the release layer forming step is described as "in-line", it means that the release layer forming step was performed between the longitudinal stretching step and the lateral stretching step, as in Example 1 above. If the process for forming a release layer is described as "off-line", a biaxially stretched film containing a particle-containing layer and a polyester base material is prepared, the film is wound up, and the release layer is formed after unrolling. It means what you did.

It is presumed that the release films of Examples 1 to 14 can produce ceramic green sheets with less color unevenness in the black layer and reduced thickness unevenness. Further, according to the release films of Examples 1 to 14, ceramic green sheets with fewer uneven defects could be produced.

On the other hand, the release films of Comparative Examples 1 and 2 have a pre-peak temperature of over 225°C measured by DSC and a variation in crystallinity in the width direction of over 5.0%, so the release films of Comparative Examples 1 and 2 are ceramics with large thickness irregularities. It is assumed that a green sheet was produced, and furthermore, many uneven defects were observed in the produced ceramic green sheet.
Although the release film of Comparative Example 3 has a variation in crystallinity in the width direction of 5.0% or less, the pre-peak temperature measured by DSC is over 225°C, so the produced ceramic green sheet has unevenness defects. were seen frequently.
The release film of Comparative Example 4 had a pre-peak temperature of less than 160°C as measured by DSC, and the variation in crystallinity in the width direction was more than 5.0%, so a ceramic green sheet with large thickness unevenness was produced. It was assumed that this would happen.

10: Ceramic green sheet 12: One surface of ceramic green sheet

Claims (10)

A release film for producing ceramic green sheets comprising a polyester base material and a release layer,
Having a film width of 1 m or more,
The thickness of the polyester base material is 40 times or more the thickness of the release layer,
The pre-peak temperature measured by differential scanning calorimetry is 160°C or more and 225°C or less,
The variation in crystallinity in the film width direction is 5.0% or less,
Release film for ceramic green sheet production. The ceramic according to claim 1, wherein a variation in heat shrinkage rate in a direction perpendicular to the film width direction and a variation in heat shrinkage rate in the film width direction are both 0.03% to 0.50%. Release film for green sheet production. The release film for producing ceramic green sheets according to claim 1, having an intrinsic viscosity (IV) of 0.65 dL/g or more. The release film for producing ceramic green sheets according to claim 1, wherein the polyester substrate is substantially free of particles. further including a particle-containing layer,
The release film for producing a ceramic green sheet according to claim 1, comprising the release layer, the polyester base material, and the particle-containing layer in this order. The release film for producing a ceramic green sheet according to claim 5, wherein the particle-containing layer contains a non-polyester resin. The release film for producing a ceramic green sheet according to claim 6, wherein the non-polyester resin is at least one resin selected from the group consisting of acrylic resin, urethane resin, and olefin resin. The release film for producing a ceramic green sheet according to claim 5, wherein the particle-containing layer has a maximum protrusion height Sp of 800 nm or less. A method for producing a release film for producing a ceramic green sheet comprising a polyester base material and a release layer, the method comprising:
Including a heat setting step of heating a polyester film having a film width of 1 m or more,
In the heat-setting step, the maximum film surface temperature of the polyester film is controlled in the range of 160 ° C. or more and 225 ° C. or less, and the dispersion of the maximum film surface temperature in the film width direction is controlled to be 5.0 ° C. or less. A method for producing a release film for producing ceramic green sheets. A laminate comprising the release film for producing a ceramic green sheet according to any one of claims 1 to 8, and a layer containing ceramic.