JP7645109B2 - Release film for ceramic green sheet manufacturing process - Google Patents

Description

The present invention relates to a release film used in the process of manufacturing ceramic green sheets.

Conventionally, multilayer ceramic products such as multilayer ceramic capacitors and multilayer ceramic substrates have been manufactured by forming ceramic green sheets, stacking multiple of the resulting ceramic green sheets, and firing them.

The ceramic green sheet is formed by applying a ceramic slurry containing ceramic materials such as barium titanate and titanium oxide onto a release film. The release film is required to have sufficient releasability to be peeled off from the thin ceramic green sheet formed on the release film with an appropriate peeling force without cracking or breaking.

The release film is usually made by treating a film-like substrate with a release agent to form a release agent layer (Patent Documents 1 and 2).

JP 2020-49803 A Patent No. 6610810

In recent years, there has been a demand for more precise and smaller laminated ceramic products, and the ceramic green sheets being formed are becoming thinner. The thinner the sheets are, the more difficult it becomes to peel the ceramic green sheets from the release film. For this reason, there is a demand for release films that make it easier to peel the ceramic green sheets.

The inventors noticed that when a molded ceramic green sheet is cut on a release film, the edge of the ceramic green sheet (hereinafter sometimes referred to as the "cut portion") that is generated when the ceramic green sheet is divided by the cutting blade is in a state of floating above the release film. In particular, the inventors discovered that this "floating" can be effectively used as a starting point for peeling off the ceramic green sheet.

The present invention was made in consideration of these circumstances, and aims to provide a release film for use in the ceramic green sheet manufacturing process that makes it easy to peel off ceramic green sheets.

In order to achieve the above object, first, the present invention provides a release film for use in the ceramic green sheet manufacturing process, comprising a substrate and a release agent layer provided on one side of the substrate, characterized in that, in a load-displacement curve measured when a load of 20 mN is applied to the release agent layer side of the release film for use in the ceramic green sheet manufacturing process using a micro-surface hardness tester, the elastic deformation power is 45% or more, the elastic displacement is 1.90 μm or less, and the plastic displacement is 1.12 μm or less (Invention 1).

In the above invention (Invention 1), it is preferable that the base material contains a filler (Invention 2).

In the above invention (Invention 2), it is preferable that the filler is a hydroxyapatite-based filler (Invention 3).

In the above inventions (Inventions 2 and 3), it is preferable that the substrate comprises at least a first resin layer containing the filler, and a second resin layer laminated on one side of the first resin layer and not containing the filler (Invention 4).

In the above inventions (Inventions 1 to 4), it is preferable that the arithmetic mean roughness (Ra) of the release agent layer on the surface opposite to the substrate is 1 nm or more and 20 nm or less (Invention 5).

In the above inventions (Inventions 1 to 5), it is preferable that the maximum projection height (Rp) of the release agent layer on the surface opposite the substrate is 10 nm or more and 200 nm or less (Invention 6).

In the above inventions (Inventions 1 to 6), it is preferable that the thickness of the release agent layer is 10 nm or more and 1000 nm or less (Invention 7).

In the above inventions (Inventions 1 to 7), it is preferable that the thickness of the substrate is 10 μm or more and 100 μm or less (Invention 8).

When the ceramic green sheet is cut on the release film for use in the ceramic green sheet manufacturing process of the present invention, lifting is likely to occur at the cut portion. This lifting can be effectively used as a trigger for peeling off the ceramic green sheet. Therefore, the release film for use in the ceramic green sheet manufacturing process of the present invention makes it easy to peel off the ceramic green sheet.

1 is a cross-sectional view of a release film for use in a ceramic green sheet manufacturing process according to one embodiment of the present invention. FIG. 2 is a cross-sectional view showing a schematic view of a ceramic green sheet being cut on a release film for a ceramic green sheet manufacturing process according to one embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view showing a schematic view of a ceramic green sheet being cut on a release film for a ceramic green sheet manufacturing process according to one embodiment of the present invention. FIG. 1 is an enlarged cross-sectional view that illustrates a schematic view of a ceramic green sheet being cut on a release film for use in a conventional ceramic green sheet manufacturing process. FIG. 2 is a schematic diagram showing a load-displacement curve.

Hereinafter, an embodiment of the present invention will be described.
1 is a cross-sectional view of an example of a release film for use in the ceramic green sheet manufacturing process according to this embodiment. As shown in the figure, a release film for use in the ceramic green sheet manufacturing process according to this embodiment (hereinafter, sometimes simply referred to as a "release film") 1 includes a substrate 11 and a release agent layer 12 provided on one side of the substrate 11. The release film 1 according to this embodiment may further include an intermediate layer between the substrate 11 and the release agent layer 12.

In the release film 1 according to this embodiment, in the load-displacement curve measured when a load of 20 mN is applied to the release agent layer 12 side of the release film 1 using a micro-surface hardness tester, the elastic deformation power is 45% or more, the elastic displacement is 1.90 μm or less, and the plastic displacement is 1.12 μm or less.

The release film 1 according to the present embodiment, which satisfies these physical properties, can effectively generate a lift at the cut portion of the ceramic green sheet when the molded ceramic green sheet is cut on the release film 1. FIG. 2 shows a schematic diagram of such cutting. As shown in the figure, cutting is performed using a cutting blade 4 with the laminate of the molded ceramic green sheet 2 and the release film 1 placed on a support table 3. At this time, the cutting blade 4 is inserted from the surface on the ceramic green sheet 2 side and pressed down until a part of the release film 1 is cut. This causes the ceramic green sheet 2 to be completely cut. When the release film 1 according to the present embodiment is used, a "lift 5" is easily generated in which the end of the ceramic green sheet 2 is locally separated from the release film 1 at the position (cut portion) where the cutting blade 4 has entered. This lift 5 can be effectively used as a starting point for separating the ceramic green sheet 2 and the release film 1 after cutting. In other words, only the release film 1 can be easily grasped at the position of this float 5, and the ceramic green sheet 2 and the release film 1 can be easily separated without applying unnecessary load to the ceramic green sheet 2.

As described above, the reasons why the release film 1 according to this embodiment is prone to have the lifting 5 are thought to be as follows. However, the reasons are not limited to the following, and the possibility of a combination of other phenomena or a completely different reason being present is not denied.

Figure 3 shows a schematic diagram of the ceramic green sheet 2 being cut by the release film 1 according to this embodiment. In particular, Figure 3 is an enlarged view of the portion to be cut. In the release film 1 according to this embodiment, by satisfying the above-mentioned physical properties, when the cutting blade 4 is pressed in as shown in Figure 3(a), the ceramic green sheet 2 is difficult to follow the release film 1. As a result, the edge generated by the cutting of the ceramic green sheet 2 is well separated from the release film 1, and a lift 5 is generated. Furthermore, as shown in Figure 3(b), when the cutting blade 4 is pulled back, the release film 1 according to this embodiment is restored with force, and the distance between the edge of the ceramic green sheet 2 and the release film 1 (the distance indicated by "h" in the figure; hereinafter, sometimes referred to as the "height" of the lift 5) becomes larger. As a result, in the release film 1 according to this embodiment, a large lift 5 is generated, and the ceramic green sheet 2 can be well peeled off.

On the other hand, FIG. 4 shows a schematic diagram of the cutting of the ceramic green sheet 2 with the conventional release film 1'. In particular, FIG. 4 shows an enlarged view of the part to be cut. With the conventional release film 1', when the cutting blade 4 is pressed in as shown in FIG. 4(a), the ceramic green sheet 2 follows the release film 1. As a result, the edge of the ceramic green sheet 2 resulting from the cutting remains almost in close contact with the release film 1, and good lifting 5 does not occur. Furthermore, as shown in FIG. 4(b), when the cutting blade 4 is pulled back, the restoration of the conventional release film 1' is insufficient, and the distance between the edge of the ceramic green sheet 2 and the release film 1' (the distance indicated by "h'" in the figure) is not sufficiently large. As a result, it is difficult to peel off the ceramic green sheet 2 with the conventional release film 1'.

In the release film 1 according to this embodiment, the elastic deformation power in the load-displacement curve measured when a load of 20 mN is applied to the release agent layer 12 in the release film 1 using a micro-surface hardness tester (hereinafter sometimes simply referred to as "elastic deformation power") is 45% or more, preferably 48% or more, and more preferably 50% or more. By having the lower limit of the elastic deformation power within the above range, the release film 1 is easily restored even if it is deformed by the force applied when cutting the ceramic green sheet. As a result, when the ceramic green sheet 2 is cut, a lift 5 is easily generated in the ceramic green sheet 2 at the cut portion, resulting in better releasability.

The release film 1 according to this embodiment preferably has an elastic deformation power of 55% or less, more preferably 53% or less, and even more preferably 52% or less. By setting the upper limit of the elastic deformation power within the above range, wear of the cutting blade 4 can be easily suppressed. The method for calculating the elastic deformation power is as shown in the test example described later.

In the release film 1 according to this embodiment, the elastic displacement in the load-displacement curve measured when a load of 20 mN is applied to the release agent layer 12 in the release film 1 using a micro-surface hardness tester (hereinafter, sometimes simply referred to as "elastic displacement") is 1.90 μm or less. By setting the upper limit of the elastic displacement within the above range, the brittleness of the release film 1 is suppressed, and the tensile strength of the release film cut into by cutting is maintained, resulting in good processability of the ceramic green sheet 2.

The release film 1 according to this embodiment preferably has an elastic displacement of 1.50 μm or more, more preferably 1.70 μm or more, and even more preferably 1.80 μm or more. When the lower limit of the elastic displacement is within the above range, the recovery distance of the release film 1 immediately after cutting is sufficient, and the height of the floating 5 of the ceramic green sheet tends to be large.

In the release film 1 according to this embodiment, the plastic displacement in the load-displacement curve measured when a load of 20 mN is applied to the release agent layer 12 in the release film 1 using a micro-surface hardness tester (hereinafter, sometimes simply referred to as "plastic displacement") is 1.12 μm or less, preferably 1.10 μm or less, and more preferably 1.08 μm or less. When the upper limit of the plastic displacement is within the above range, the edge of the ceramic green sheet 2 is less likely to follow the cutting blade 4 and be pressed into the release film 1. This makes it easier for a lift 5 to occur in the cut portion of the ceramic green sheet 2 when the ceramic green sheet is cut, resulting in better releasability.

The release film 1 according to this embodiment preferably has a plastic deformation of 1.00 μm or more, more preferably 1.02 μm or more, and even more preferably 1.04 μm or more. By setting the lower limit of the plastic deformation within the above range, it becomes easier to increase the height of the float 5.

1. Physical properties of the release film for the ceramic green sheet manufacturing process In the release film 1 according to this embodiment, the arithmetic mean roughness (Ra) on the surface of the release agent layer 12 opposite to the substrate 11 is preferably 20 nm or less, more preferably 15 nm or less, and even more preferably 10 nm or less. As the ceramic green sheet becomes thinner, the surface of the release agent layer 12 of the release film 1 is required to have higher smoothness. By setting the upper limit of the arithmetic mean roughness within the above range, a uniform ceramic green sheet can be formed. In addition, the lower limit of the arithmetic mean roughness (Ra) is not particularly limited, but is preferably 1 nm or more, more preferably 1.5 nm or more, and even more preferably 2 nm or more. The method for measuring the arithmetic mean roughness (Ra) is as shown in the test example described later.

In the release film 1 according to this embodiment, the maximum protrusion height (Rp) on the surface of the release agent layer 12 opposite the substrate 11 is preferably 200 nm or less, more preferably 150 nm or less, and even more preferably 100 nm or less. A highly stacked and highly integrated multilayer ceramic capacitor (MLCC) requires a ceramic green sheet having a thickness of 1.0 μm or less. By setting the upper limit of the maximum protrusion height within the above range, it becomes easier to suppress the occurrence of pinholes during production even if the ceramic green sheet is a thin film. In addition, the lower limit of the maximum protrusion height (Rp) is not particularly limited, but is preferably 10 nm or more, more preferably 20 nm or more, and even more preferably 30 nm or more. The method for measuring the maximum protrusion height (Rp) is as shown in the test example described later.

The peeling force required to peel the release film 1 from the ceramic green sheet formed on the release surface of the release film 1 according to this embodiment can be set as appropriate, but is preferably 100 mN/40 mm or less, more preferably 50 mN/40 mm or less, and even more preferably 30 mN/40 mm or less. By setting the upper limit of the peeling force within the above range, better peeling properties can be exhibited. In addition, the lower limit of the peeling force is preferably a peeling force that does not cause unintended peeling from the formed ceramic green sheet, for example, preferably 5 mN/40 mm or more, and especially preferably 10 mN/40 mm or more. The method for measuring the peeling force is as shown in the test example described later.

The height of the float 5 of the ceramic green sheet at the cut portion (height indicated by "h" in FIG. 3(b)) is preferably 1.0 μm or more, more preferably 1.5 μm or more, and even more preferably 2.0 μm or more. The height of the float 5 is preferably 10 μm or less, more preferably 8 μm or less, and even more preferably 5 μm or less.

2. Substrate The substrate 11 of the release film 1 according to this embodiment is not particularly limited as long as it satisfies the above-mentioned conditions regarding the load-displacement curve when the release film 1 is constructed and can be laminated with the release agent layer 12. Examples of materials for the substrate 11 include polyester-based resins such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; polyolefin-based resins such as polyethylene, polypropylene, polybutene, polybutadiene, polymethylpentene, ethylene-norbornene copolymer, and norbornene resin; propylene-based copolymers such as ethylene-polypropylene random copolymer; ethylene-based copolymers such as ethylene-(meth)acrylic acid copolymer, ethylene-methyl (meth)acrylate copolymer, and other ethylene-(meth)acrylic acid ester copolymers; ethylene-vinyl acetate copolymer; polyvinyl chloride-based resins such as polyvinyl chloride copolymers; (meth)acrylic acid ester copolymers; polyurethane; polyimide; polystyrene; polycarbonate; fluororesin, etc. In addition, crosslinked products of these or ionomers of these may be used as materials. In this specification, "(meth)acrylic acid" means both acrylic acid and methacrylic acid. The same applies to other similar terms. Among the above-mentioned materials, it is preferable to use polyester resins, particularly polyethylene terephthalate, and furthermore it is preferable to use biaxially oriented polyethylene terephthalate, from the viewpoint of easily satisfying the above-mentioned conditions regarding the load-displacement curve.

The substrate 11 may be a film made of one of the above-mentioned materials, or may be a film made of multiple types of the above-mentioned materials. Furthermore, the substrate 11 may be a laminated film made up of multiple such films. In this laminated film, the materials constituting each layer may be the same or different.

In addition, from the viewpoint of easily satisfying the conditions related to the load-displacement curve described above, it is preferable that the substrate 11 contains a filler, and in particular, it is preferable that the substrate 11 is a resin to which a filler has been added. The filler is not particularly limited as long as it enables the conditions related to the load-displacement curve described above to be achieved, and may be an inorganic filler or an organic filler. In particular, the filler is preferably an inorganic filler, and examples of such fillers include silica, hydroxyapatite, titanium oxide, calcium carbonate, kaolin, and aluminum oxide. Among these, hydroxyapatite-based fillers are preferable. These fillers may be used alone or in combination of two or more types.

The average particle size of the filler is preferably 100 nm or more, more preferably 200 nm or more, and even more preferably 300 nm or more. The average particle size of the filler is preferably 2000 nm or less, more preferably 1800 nm or less, and even more preferably 1500 nm or less. When the average particle size of the filler is within the above range, the resulting release film 1 is more likely to satisfy the conditions regarding the load-displacement curve described above.

When the substrate 11 contains a filler (when the substrate 11 contains a filler throughout its entirety; excluding the case where the substrate 11 has a first resin layer described below), the content of the filler in the substrate 11 is preferably 0.5% by mass or more, and more preferably 0.6% by mass or more. The content of the filler is preferably 1.5% by mass or less, and more preferably 1.4% by mass or less. When the content of the filler is within the above range, the obtained release film 1 is more likely to satisfy the conditions related to the load-displacement curve described above.

It is also preferable that the substrate 11 has at least a layer (first resin layer) containing a filler and a layer (second resin layer) laminated on one side of the first resin layer and not containing a filler. By having the first resin layer and the second resin layer in this way, the release film 1 composed of the substrate 11 is more likely to satisfy the conditions related to the load-displacement curve described above. The first resin layer and the second resin layer may each be provided in the substrate 11 in one layer, or in two or more layers. A typical example is a substrate 11 in which the first resin layer, the second resin layer, and the first resin layer are laminated in this order.

The method for producing the substrate 11 is not particularly limited as long as it is possible to satisfy the conditions related to the load-displacement curve described above, and it can be produced, for example, by a general method. For example, the substrate 11 can be obtained by forming the above-mentioned resin into a film shape by melt extrusion molding, calendaring, etc.

In addition, when manufacturing a substrate 11 containing the above-mentioned filler (substrate 11 without a second resin layer), the substrate 11 can be obtained by adding the filler to the above-mentioned resin and forming it into a film in the same manner as above.

The manufacturing method of the substrate 11 having the first resin layer and the second resin layer is not particularly limited. For example, when the above-mentioned resin is extruded, the filler is supplied to the surface of the resin layer immediately after it is formed into a film, and the filler is unevenly distributed only in the surface layer of the resin layer, thereby obtaining the substrate 11. In this case, the first resin layer is formed as the surface layer in which the filler is present, and the second resin layer is formed as the central layer in which the filler is not present. As another manufacturing method, first, a resin to which a filler is added (resin for the first resin layer) and a resin to which a filler is not added (resin for the second resin layer) are prepared, and then the resins are co-extruded to obtain the substrate 11. Alternatively, the substrate 11 may be obtained by forming each of these resins into a film and then laminating the obtained layers.

In order to improve adhesion to the release agent layer 12 and the like provided on the surface of the substrate 11, one or both sides of the substrate 11 may be subjected to a surface treatment such as an oxidation method or a roughening method, or a primer treatment, as desired. Examples of the oxidation method include corona discharge treatment, plasma discharge treatment, chromium oxidation treatment (wet), flame treatment, hot air treatment, ozone treatment, and ultraviolet irradiation treatment, and examples of the roughening method include sandblasting and thermal spraying treatment. These surface treatment methods are appropriately selected depending on the type of substrate 11, but generally, corona discharge treatment is preferably used in terms of effectiveness and operability.

The breaking stress in the width direction of the substrate 11 (the direction perpendicular to the flow direction during the manufacture of the substrate 11; hereinafter sometimes referred to as the "TD direction") is preferably 200 MPa or more, more preferably 220 MPa or more, and even more preferably 240 MPa or more. The breaking stress in the width direction of the substrate 11 is preferably 340 MPa or less, more preferably 320 MPa or less, and even more preferably 320 MPa or less. By having the breaking stress of the substrate 11 in the above range, the strength required in each process is sufficiently maintained, the crystallinity of the resin is increased, and the release film 1 is easily able to achieve a large elastic deformation power. The details of the method for measuring the breaking stress are as described in the examples below.

The breaking elongation in the width direction (TD) of the substrate 11 is preferably 80% or more, more preferably 85% or more, and even more preferably 90% or more. The breaking elongation in the width direction of the substrate 11 is preferably 120% or less, more preferably 110% or less, and even more preferably 105% or less. When the breaking elongation of the substrate 11 is in the above range, the release film 1 is less likely to be plastically deformed, and the release film 1 is less likely to be cut by the cutting blade 4, which improves the cuttability of the ceramic green sheet 2. The details of the method for measuring the breaking elongation are as described in the examples below.

The thickness of the substrate 11 is preferably 10 μm or more, more preferably 15 μm or more, and even more preferably 20 μm or more. The thickness of the substrate 11 is preferably 100 μm or less, more preferably 50 μm or less, and even more preferably 38 μm or less. By having the thickness of the substrate 11 within the above range, the resulting release film 1 is more likely to satisfy the conditions regarding the load-displacement curve described above.

3. Release Agent Layer The release agent constituting the release agent layer 12 is not particularly limited as long as it satisfies the above-mentioned conditions regarding the load-displacement curve when the release film 1 is formed. For example, a silicone-based release agent, a fluorine-based release agent, an acrylic-based release agent, an alkyd-based release agent, a long-chain alkyl group-based release agent, a thermoplastic resin-based release agent, etc. can be used. Among them, it is preferable to use a silicone-based release agent as the release agent constituting the release agent layer 12. These release agents may be used alone or in combination of two or more.

As the silicone-based release agent, any of the following types may be used: addition reaction type, condensation reaction type, ultraviolet curing type, electron beam curing type, etc. Among these, addition reaction type silicone-based release agents are particularly preferred because they have high reactivity and excellent productivity, as well as excellent effects such as little change in release force over time and no cure shrinkage.

An example of an addition reaction type silicone-based release agent is a release agent composition that contains a base agent made of a polyorganosiloxane compound containing an alkenyl group and a catalyst that promotes the addition reaction. The release agent composition may further contain a crosslinking agent.

The main skeleton of the polyorganosiloxane compound constituting the base agent or crosslinking agent may be, for example, polydimethylsiloxane or a dimethylsiloxane-methylphenylsiloxane copolymer. Examples of alkenyl groups used in the polyorganosiloxane base agent include alkenyl groups having 2 to 10 carbon atoms, such as vinyl groups, allyl groups, propenyl groups, and hexenyl groups. The position of the alkenyl group in the polyorganosiloxane may be the molecular terminal or a side chain. It is preferable that the polyorganosiloxane base agent has two or more alkenyl groups per molecule.

The weight average molecular weight of the polyorganosiloxane as the base agent is preferably 50,000 or more, particularly preferably 100,000 or more, and more preferably 150,000 or more. The weight average molecular weight is preferably 1,000,000 or less, particularly preferably 800,000 or less, and more preferably 600,000 or less. The weight average molecular weight in this specification is a value calculated in terms of standard polystyrene measured by gel permeation chromatography (GPC).

By having the weight average molecular weight of the polyorganosiloxane in the above range, it becomes easier to achieve excellent coating properties. In addition, by having the weight average molecular weight of the polyorganosiloxane be 50,000 or more, it is possible to prevent the coating viscosity of the release agent composition from becoming too low, suppressing the occurrence of repelling, and making it easier to obtain a release agent layer 12 with a uniform surface condition. Furthermore, by having the weight average molecular weight of the polyorganosiloxane be 1,000,000 or less, it is possible to effectively suppress an increase in the coating viscosity of the release agent composition, and it is possible to ensure good solubility in the dilution solvent.

Specific examples of polyorganosiloxanes used in the crosslinking agent include dimethylhydrogensiloxane-methylhydrogensiloxane copolymers endblocked with dimethylhydrogensiloxane and trimethylsiloxy group, methylhydrogenpolysiloxane endblocked with trimethylsiloxy group, and poly(hydrogensilsesquioxane).

The catalyst is not particularly limited as long as it can cure the stripping agent composition, but specific examples include particulate platinum, particulate platinum adsorbed on a carbon powder carrier, chloroplatinic acid, alcohol-modified chloroplatinic acid, olefin complexes of chloroplatinic acid, platinum metal compounds such as palladium and rhodium, etc. The content of the catalyst is preferably about 1 ppm or more and 1000 ppm or less based on the total amount of components other than the catalyst.

Furthermore, the addition reaction type silicone-based release agent may contain an addition reaction inhibitor, a release adjuster, an adhesion improver, etc., if desired. In addition to the release agent, antistatic agents, dyes, pigments, and other additives may also be used as materials constituting the release agent layer 12.

The thickness of the release agent layer 12 is preferably 10 nm or more, more preferably 15 nm or more, and even more preferably 20 nm or more. The thickness of the release agent layer 12 is preferably 1000 nm or less, more preferably 800 nm or less, and even more preferably 500 nm or less. By having the thickness of the release agent layer 12 within the above range, the obtained release film 1 is more likely to satisfy the conditions regarding the load-displacement curve described above.

4. Intermediate Layer In the release film 1 according to the present embodiment, in order to make it easier to satisfy the conditions related to the load-displacement curve described above, an intermediate layer may be provided between the substrate 11 and the release agent layer 12. The material of the intermediate layer is not particularly limited, but examples thereof include ultraviolet curing resins, melamine resins, epoxy resins, alkyd resins, and urea resins.

When the release film 1 has an intermediate layer, the thickness of the intermediate layer is preferably 10 μm or more, particularly preferably 15 μm or more, and more preferably 20 μm or more. The thickness of the intermediate layer is preferably 1000 μm or less, particularly preferably 800 μm or less, and more preferably 500 μm or less. By having the thickness of the intermediate layer within the above range, the obtained release film 1 is more likely to satisfy the conditions regarding the load-displacement curve described above.

5. Manufacturing Method of Release Film for Ceramic Green Sheet Manufacturing Process The release film 1 according to this embodiment can be obtained, for example, by applying a coating liquid containing a release agent composition and, if desired, an organic solvent to one surface of a substrate 11, followed by drying and curing to form a release agent layer 12. Examples of the coating method that can be used include gravure coating, bar coating, spray coating, spin coating, knife coating, roll coating, and die coating.

There are no particular limitations on the organic solvent, and various types can be used. For example, hydrocarbon compounds such as toluene, hexane, and heptane, as well as acetone, ethyl acetate, methyl ethyl ketone, methyl isobutyl ketone, and mixtures thereof can be used.

The coating film obtained by applying the release agent composition as described above is preferably thermally cured. In this case, the heating temperature is preferably 90°C or higher and 140°C or lower, and the heating time is preferably about 10 seconds or higher and 120 seconds or lower. If necessary, the curing of the release agent composition may be accelerated by irradiating it with ultraviolet light.

When the release film 1 according to this embodiment has an intermediate layer, the intermediate layer can be formed on one side of the substrate 11 using a general method according to the material of the intermediate layer. After that, the release agent layer 12 can be formed on the side of the intermediate layer opposite the substrate 11 by the above-mentioned method, thereby obtaining the release film 1.

6. Method of using the release film for the ceramic green sheet manufacturing process The release film 1 according to this embodiment can be used to manufacture a ceramic green sheet. Specifically, a ceramic slurry containing a ceramic material such as barium titanate or titanium oxide is applied to the release surface of the release agent layer 12, and then the ceramic slurry is dried to obtain a ceramic green sheet. Coating can be performed, for example, using a slot die coating method or a doctor blade method.

Examples of binder components contained in the ceramic slurry include butyral resins and acrylic resins. Examples of solvents contained in the ceramic slurry include organic solvents and aqueous solvents.

After forming the ceramic green sheet, the ceramic green sheet can be cut on the release film 1. This cutting can be performed by a general method. Following this cutting, the release film 1 is peeled off from the ceramic green sheet.

The release film 1 according to this embodiment satisfies the conditions related to the load-displacement curve described above, so that when the release film 1 is cut, the lift 5 is likely to occur in the cut portion of the ceramic green sheet 2. Then, when the release film 1 is peeled off from the ceramic green sheet 2, the lift 5 can be used as the starting point. Therefore, the release film 1 according to this embodiment makes it possible to easily peel off the ceramic green sheet 2.

The above-described embodiments are described to facilitate understanding of the present invention, and are not described to limit the present invention. Therefore, each element disclosed in the above embodiments is intended to include all design modifications and equivalents that fall within the technical scope of the present invention.

For example, other layers such as an antistatic layer may be provided on the surface of the substrate 11 opposite the release agent layer 12, or between the substrate 11 and the release agent layer 12.

The present invention will be explained in more detail below with reference to examples, but the scope of the present invention is not limited to these examples.

[Preparation of substrate]
The following substrates A to G were prepared. Among these, substrates A to F were obtained by forming a film by changing the amount and type of filler added to polyethylene terephthalate.
<Substrate A>
Main material: polyethylene terephthalate, filler: hydroxyapatite, thickness: 31 μm, breaking stress (MD direction): 237 MPa, breaking stress (TD direction): 287 MPa, breaking elongation (MD direction): 152%, breaking elongation (TD direction): 100%
<Substrate B>
Main material: polyethylene terephthalate, filler: hydroxyapatite, thickness: 31 μm, breaking stress (MD direction): 237 MPa, breaking stress (TD direction): 287 MPa, breaking elongation (MD direction): 152%, breaking elongation (TD direction): 100%
<Substrate C>
Main material: polyethylene terephthalate, filler: hydroxyapatite, thickness: 31 μm, breaking stress (MD direction): 235 MPa, breaking stress (TD direction): 281 MPa, breaking elongation (MD direction): 145%, breaking elongation (TD direction): 97%
<Substrate D>
Main material: polyethylene terephthalate, filler: silica, thickness: 31 μm, breaking stress (MD direction): 232 MPa, breaking stress (TD direction): 285 MPa, breaking elongation (MD direction): 129%, breaking elongation (TD direction): 84%
<Substrate E>
Main material: polyethylene terephthalate, filler: silica, thickness: 31 μm, breaking stress (MD direction): 239 MPa, breaking stress (TD direction): 282 MPa, breaking elongation (MD direction): 145%, breaking elongation (TD direction): 102%
<Substrate F>
Main material: polyethylene terephthalate, filler: silica, thickness: 31 μm, breaking stress (MD direction): 233 MPa, breaking stress (TD direction): 280 MPa, breaking elongation (MD direction): 140%, breaking elongation (TD direction): 99%

The breaking stress and breaking elongation were measured by a tensile test using a tensile tester (manufactured by Orientec Co., Ltd., product name "Tensilon") in an environment of 23°C and 50% RH, at a tensile speed of 200 mm/min.

Example 1
As the polyorganosiloxane, 100 parts by mass of a polyorganosiloxane having two or more vinyl groups at the terminal or side chain, and the portion not having a vinyl group being a methyl group (weight average molecular weight: 390,000, vinyl group amount in 1 g of polyorganosiloxane: 0.25 mmol, solid content: 30 mass%) was dissolved in toluene to obtain an addition reaction type polyorganosiloxane solution with a solid content of 1.5 mass%. Next, 2 parts by mass of a platinum-based catalyst (manufactured by Dow Corning Toray Co., Ltd., product name: SRX-212) was added to and mixed with 100 parts by mass of the addition reaction type polyorganosiloxane solution to obtain a coating solution of a release agent composition with a solid content of 1.5 mass%.

The obtained coating solution of the release agent composition was uniformly applied to one side of the substrate A obtained in Preparation Example 1 using a bar coater. The substrate was then dried by heating at 125°C for 60 seconds to harden the release agent composition, thereby obtaining a release film for use in the ceramic green sheet manufacturing process in which a release agent layer having a thickness of 50 nm was laminated on the substrate.

[Examples 2 to 3, Comparative Examples 1 to 5]
Release films for use in the production process of ceramic green sheets were obtained in the same manner as in Example 1, except that the type of substrate and the thickness of the release agent layer were changed as shown in Table 1.

[Test Example 1] (Measurement of elastic displacement, plastic displacement and elastic deformation power using a micro surface hardness tester)
Using a micro-surface hardness tester (manufactured by Shimadzu Corporation, product name: Dynamic Ultra-Micro Hardness Tester W201S), an indenter was pressed with a load of 20 mN against the surface of the release agent layer side of the release film for the ceramic green sheet manufacturing process produced in the examples and comparative examples, and a load-displacement curve was obtained showing the relationship between the indentation depth displacement and the load.

Figure 5 shows a schematic of the load-displacement curve obtained. In this load-displacement curve, the load (F) is plotted on the vertical axis and the indentation depth displacement (d) is plotted on the horizontal axis. As shown in the figure, when the load is increased from the start when no load is applied until the maximum load is applied, the displacement progresses from point P0 to point P1 (the displacement amount at this time is designated "d1") as shown by solid line A. When the load is then removed, the displacement progresses from point P1 to point P2 (the displacement amount at this time is designated "d2") as shown by solid line B. Note that the intersection point of the perpendicular line (dashed line C) to point P1 and the horizontal axis is designated as point P3.

In the load-displacement curve, the displacement d1 at the maximum load (point P1) was defined as the elastic displacement, and the displacement d2 at the load-removal (point P2) was defined as the plastic displacement. The elastic deformation power was measured by deriving W _plast (plastic deformation work) as the area of the range surrounded by the solid line A, the solid line B, and the horizontal axis from the load-displacement curve, and W _elast (elastic deformation work) as the area of the range surrounded by the solid line B, the dashed line C, and the horizontal axis, and deriving the elastic deformation power (ηIT) from the ratio of the elastic deformation work to W _total (total deformation work) using the following formulas (1) and (2). The results are shown in Table 1.
W _total = W _plast + W _elast ... (1)
ηIT=W _elast /W _total ...(2)

[Test Example 2] (Measurement of arithmetic mean roughness and maximum projection height of release agent layer)
A double-sided tape was applied to a glass plate, and the release film obtained in the examples and comparative examples was fixed to the glass plate via the double-sided tape so that the opposite side to the side to be measured was the glass plate side. The arithmetic mean roughness (Ra; nm) and maximum protrusion height (Rp; nm) of the release surface and back surface of the release film were observed at 50 magnification in PSI mode using an optical interference surface profile observation device (manufactured by Veeco, product name: WYKO-1100), and were measured based on the surface profile image obtained in the range of 91.2 × 119.8 μm. The results are shown in Table 1.

[Test Example 3] (Evaluation of slurry coatability)
A ceramic slurry was prepared by adding 135 parts by mass of a toluene/ethanol mixed solvent (mass ratio 6/4) to 100 parts by mass of barium titanate powder ( _BaTiO3 ; manufactured by Sakai Chemical Industry Co., Ltd., product name: BT-03), 8 parts by mass of polyvinyl butyral (manufactured by Sekisui Chemical Co., Ltd., product name: S-LEC B KBM-2) as a binder, and 4 parts by mass of dioctyl phthalate (manufactured by Kanto Chemical Co., Ltd., product name: dioctyl phthalate grade 1) as a plasticizer, and mixing and dispersing the mixture in a ball mill.

The above-mentioned ceramic slurry was applied to the surface of the release agent layer of the release film for the ceramic green sheet manufacturing process obtained in the examples and comparative examples using a die coater, and then dried at 80°C for 1 minute. In this way, a ceramic green sheet having a thickness of 3 μm was formed on the release film, and a release film with a ceramic green sheet was obtained. For this release film with a ceramic green sheet, a fluorescent lamp was illuminated from the release film side, and all the formed ceramic green sheet surfaces were visually inspected, and the slurry coatability was evaluated according to the following criteria. The results are shown in Table 1.
◯: No pinholes were present in the ceramic green sheet. ×: Pinholes were present in the ceramic green sheet.

[Test Example 4] (Measurement of peel strength from ceramic green sheet)
The release film with the ceramic green sheet produced by the same procedure as in Test Example 3 was left for 24 hours in an atmosphere of room temperature 23 degrees and humidity 50%. Next, it was cut into a size of 100 mm in the flow direction and 40 mm in the width direction. This was used as a measurement sample. An acrylic adhesive tape (manufactured by Nitto Denko Corporation, product name: 31B tape) with a width of 5 mm was attached to one end of the short side of the ceramic green sheet side of the measurement sample. The release film side of this measurement sample was fixed to a flat plate with double-sided tape, and the flat plate was placed horizontally on a peel tester (manufactured by Shimadzu Corporation, product name: AGS-20NX) so that the measurement sample was on the upper surface. Then, the end of the ceramic green sheet on the side where the acrylic adhesive tape was attached was peeled off from the release film, and the end was attached to the jig of the peel tester. In this state, the ceramic green sheet was pulled vertically upward (90° peeling) at a peeling speed of 200 mm/min to peel the release film from the ceramic green sheet, and the force required for peeling (peel force; mN/40 mm) was measured. The results are shown in Table 1.

[Test Example 5] (Evaluation of sheet lifting)
Using a texture analyzer (manufactured by Eiko Seiki Co., Ltd., product name: TA.XT.plus), a sheet lifting test was performed by pressing a Thomson blade from the ceramic green sheet side into a release film with a ceramic green sheet produced by the same procedure as in Test Example 3 under the following measurement conditions. Using a high-speed camera (manufactured by Keyence Corporation, product name: VW-5000), the ceramic green sheet lifting was evaluated according to the following evaluation criteria.
[Measurement conditions]
・Blade material: Carbide (FM10K)
Blade angle: 42 degrees Blade tip width: 2 μm
Push-in speed: 0.5 mm/s
[Evaluation Criteria for Sheet Lifting]
.largecircle.: When the blade came into contact with the substrate, the ceramic green sheet was lifted by 1.0 μm or more at the cut portion.
×: The lift of the ceramic green sheet at the cut portion when the blade came into contact with the substrate was less than 1.0 μm.

After the sheet lifting test, the samples were observed through the release film using a digital microscope (Keyence Corporation, product name: VHX-1000) to measure the height of the sheet lifting (height indicated by "h" in Figure 3(b)). The results are shown in Table 1.

As is clear from Table 1, the release film for the ceramic green sheet manufacturing process obtained in the examples caused good lifting when the ceramic green sheet was cut.

The release film for the ceramic green sheet manufacturing process of the present invention is suitable for forming ceramic green sheets.

REFERENCE SIGNS LIST 1... Release film 11... Substrate 12... Release agent layer 2... Ceramic green sheet 3... Support 4... Cutting blade 5... Float

Claims (6)

A release film for a ceramic green sheet manufacturing process, comprising a substrate and a release agent layer provided on one side of the substrate,
The substrate is made of a polyester resin and contains a hydroxyapatite filler.
A release film for a ceramic green sheet manufacturing process, characterized in that, in a load-displacement curve measured when a load of 20 mN is applied to the release agent layer side of the release film for the ceramic green sheet manufacturing process using a micro-surface hardness tester, the elastic deformation power is 45% or more, the elastic displacement amount is 1.90 μm or less, and the plastic displacement amount is 1.12 μm or less. 2. The release film for a ceramic green sheet manufacturing process according to claim 1, characterized in that the base material comprises at least a first resin layer containing the filler, and a second resin layer laminated on one side of the first resin layer and not containing the filler. 3. The release film for use in a ceramic green sheet manufacturing process according to claim 1, wherein the release agent layer has an arithmetic mean roughness (Ra) of 1 nm or more and 20 nm or less on the surface opposite to the substrate. The release film for use in a ceramic green sheet manufacturing process according to any one of claims 1 to 3 , characterized in that the maximum projection height (Rp) of the release agent layer on the surface opposite to the substrate is 10 nm or more and 200 nm or less. 5. The release film for use in a ceramic green sheet production process according to claim 1 , wherein the release agent layer has a thickness of 10 nm or more and 1000 nm or less. 6. The release film for use in a ceramic green sheet manufacturing process according to claim 1 , wherein the thickness of the substrate is 10 μm or more and 100 μm or less.

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