Peeling film and production method for ceramic green sheet

Abstract

A peeling film according to the present invention comprises a base material and a peeling agent layer that is provided on one side of the base material. When a peeling-force-measurement coating liquid is used to form a peeling-force-measurement sheet that has a thickness of 3 μm on the surface of the peeling agent layer on the reverse side from the base material to produce a laminate of the peeling film and the peeling-force-measurement sheet and the peeling force for peeling the peeling-force-measurement sheet from the peeling film is measured under different temperature conditions from 70°C to 100°C, a maximum peeling force that is the highest measured value is less than 100 mN / 40 mm. The surface free energy at the surface of the peeling agent layer on the reverse side from the base material is at least 23 mN / m2. The peeling film makes it possible to favorably peel a ceramic green sheet or the like, even when a heated jig is being used, and also has excellent slurry coatability.

Description

Method for manufacturing release film and ceramic green sheet

[0001] This invention relates to a release film suitable for use in the process of manufacturing ceramic green sheets, and to a method for manufacturing ceramic green sheets.

[0002] Conventionally, the manufacturing of multilayer ceramic products such as multilayer ceramic capacitors and multilayer ceramic substrates involves forming ceramic green sheets, stacking multiple of these sheets, and then firing them.

[0003] Ceramic green sheets are formed by coating a ceramic slurry containing ceramic materials such as barium titanate and titanium oxide onto a release film. The release film used is one in which a silicone-based compound such as polysiloxane has been treated to release the film substrate. This release film is required to have release properties that allow the thin ceramic green sheet formed on it to be peeled off the film without tearing or other damage.

[0004] As an example of the above-mentioned release film, Patent Document 1 discloses a release film comprising a release layer formed from a release agent composition containing melamine resin, polyorganosiloxane, polyalkylene glycol, and a dispersant.

[0005] Patent No. 7082890

[0006] Incidentally, ceramic green sheets formed on a release film may be peeled off the release film using a heated jig. For example, after peeling a ceramic green sheet from the release film using a jig, the ceramic green sheet may be laminated while it is adsorbed onto the jig. In this case, the laminate of ceramic green sheets is heated while pressing is performed with the jig, and this heating causes the jig to become hot. Then, the next ceramic green sheet may be peeled off before the jig has cooled sufficiently.

[0007] The inventors have discovered that when attempting to peel a ceramic green sheet from a release film using a heated jig as described above, the ceramic green sheet may soften and break, making it difficult to peel properly.

[0008] Furthermore, in the production of ceramic green sheets, release films must be able to coat the ceramic slurry evenly on the release surface without any splashing or repellency of the slurry.

[0009] This invention has been made in view of the above circumstances, and aims to provide a release film that can effectively peel off objects such as ceramic green sheets even when using heated jigs, and that also has excellent slurry coating properties.

[0010] To achieve the above objective, firstly, the present invention provides a release film comprising a base material and a release agent layer provided on one side of the base material, wherein a release force measuring sheet with a thickness of 3 μm is formed on the side of the release agent layer opposite to the base material using a coating solution for release force measurement containing 100 parts by mass of barium titanate, 8 parts by mass of polyvinyl butyral resin, and 4 parts by mass of dioctyl phthalate, and the maximum release force obtained by measuring the release force when the release force measuring sheet is peeled from the release film under various temperature conditions from 70°C to 100°C is less than 100 mN / 40 mm, and the surface free energy on the side of the release agent layer opposite to the base material is 23 mN / m ２ The invention provides a release film characterized by the above (Invention 1).

[0011] In the above invention (Invention 1), it is preferable that the maximum peeling force is 10 mN / 40 mm or more (Invention 2).

[0012] In the above inventions (Inventions 1 and 2), it is preferable that the pre-heating peel force measured when the peel force measuring sheet is peeled from the release film under a temperature of 23°C is 10 mN / 40 mm or more (Invention 3).

[0013] In the above invention (Invention 3), it is preferable that the absolute value of the difference between the maximum peeling force and the peeling force before heating is 35 mN / 40 mm or less (Invention 4).

[0014] In the above inventions (inventions 1 to 4), when the peeling force of the laminate is measured when the peeling force measuring sheet is peeled from the release film under various temperature conditions from 70°C to 100°C, and the minimum value of the peeling force identified is defined as the minimum peeling force, it is preferable that the difference obtained by subtracting the minimum peeling force from the maximum peeling force is 20 mN / 40 mm or less (invention 5).

[0015] In the above inventions (inventions 1 to 5), it is preferable that the arithmetic mean height Sa on the surface of the release agent layer opposite to the substrate is less than 10 nm (invention 6).

[0016] In the above inventions (Inventions 1 to 6), the release agent layer is preferably a cured product of a release agent composition containing an active energy ray curable component and a silicone-based component (Invention 7).

[0017] In the above inventions (inventions 1 to 7), it is preferable that they are for use in the ceramic green sheet manufacturing process (invention 8).

[0018] Secondly, the present invention provides a method for manufacturing a ceramic green sheet, which includes forming a ceramic green sheet on the surface of the release film (Inventions 1 to 8) on the side of the release agent layer, and peeling the ceramic green sheet from the release film using a jig heated to a temperature of 70°C or higher and 100°C or lower (Invention 9).

[0019] The release film according to the present invention can effectively peel off objects such as ceramic green sheets, even when using heated jigs, and also exhibits excellent slurry coating properties.

[0020] Embodiments of the present invention will be described below. The release film according to this embodiment comprises a substrate and a release agent layer provided on one side of the substrate.

[0021] Furthermore, the release film according to this embodiment satisfies the conditions for release force described below. First, as a prerequisite, a release force measuring sheet with a thickness of 3 μm is formed on the side of the release agent layer opposite to the substrate (hereinafter sometimes referred to as the "release surface") using a coating solution for release force measurement containing 100 parts by mass of barium titanate, 8 parts by mass of polyvinyl butyral resin, and 4 parts by mass of dioctyl phthalate. The release force of the laminate of the release force measuring sheet and the release film is measured when the release force measuring sheet is peeled from the release film under various temperature conditions from 70°C to 100°C, and the maximum value identified is defined as the "maximum release force." In the release film according to this embodiment, the maximum release force is less than 100 mN / 40 mm. Note that the thickness of the release force measuring sheet can be measured after heating as long as it is 3 μm when rounded to the first decimal place.

[0022] The inventors hypothesized that when peeling a ceramic green sheet from a release film using a heated jig, peeling defects occur because the ceramic green sheet is heated and softened by the jig, and the tensile force applied to the ceramic green sheet when peeling it from the release film causes it to break and remain on the release film.

[0023] In the release film according to this embodiment, by satisfying the above-mentioned conditions for maximum release force, it is possible to release the ceramic green sheet and other objects well without release defects even when releasing the ceramic green sheet using a heated jig.

[0024] Furthermore, from the viewpoint of enabling better peeling, the maximum peeling force is preferably 80 mN / 40 mm or less, and particularly preferably 60 mN / 40 mm or less.

[0025] On the other hand, regarding the lower limit of the maximum peeling force, from the viewpoint of easily suppressing the unintended lifting or peeling of the target, such as the ceramic green sheet, from the release film, it is preferable that it be 10 mN / 40 mm or more, particularly preferably 14 mN / 40 mm or more, and even more preferably 18 mN / 40 mm or more.

[0026] Further details regarding the measurement method for the maximum peeling force are described in the test examples below.

[0027] Furthermore, in the release film according to this embodiment, the surface free energy on the side of the release agent layer opposite to the substrate is 23 mN / m ２ That concludes the explanation. Because the surface free energy is within the above range, the occurrence of repulsion is effectively suppressed when applying the ceramic slurry to the release surface of the release film. From this perspective, the above surface free energy is 24 mN / m ２ It is preferable that the value be greater than or equal to 25 mN / m, and particularly 25 mN / m ２ It is preferable that the above is true. On the other hand, the upper limit of the surface free energy is 45 mN / m from a manufacturing standpoint. ２ The following is preferable, and in particular 40 mN / m ２ Preferably the following, and moreover 35 mN / m ２ The following is preferable. The method for measuring the surface free energy is as shown in the test examples described later, and in particular, it is measured based on the Kitazaki-Hata theory (see Kitazaki, Yasuaki et al., Journal of the Japan Adhesion Society, Vol. 8, No. 3, 1972, pp. 131-141).

[0028] 1. Substrate The substrate in this embodiment is not particularly limited, and any conventionally known substrate can be appropriately selected and used. Examples of such substrates include films made of polyester such as polyethylene terephthalate and polyethylene naphthalate, polyolefins such as polypropylene and polymethylpentene, polycarbonate, and plastics such as ethylene-vinyl acetate copolymer. These may be single layers or multilayer layers of two or more of the same or different materials.

[0029] Among the above, polyester film is preferred, polyethylene terephthalate film is particularly preferred, and biaxially oriented polyethylene terephthalate film is even more preferred. Polyethylene terephthalate film is less likely to generate dust during processing and use, and therefore can effectively prevent defects in ceramic slurry coating caused by dust, for example.

[0030] The surface of the substrate facing the release agent layer may be subjected to surface treatment such as oxidation or primer treatment in order to improve the adhesion of the release agent layer. Examples of oxidation methods include corona discharge treatment, plasma discharge treatment, chromium oxidation treatment (wet), flame treatment, hot air treatment, ozone treatment, and ultraviolet irradiation treatment. These surface treatment methods are appropriately selected depending on the type of substrate, but corona discharge treatment is generally preferred in terms of effectiveness and ease of operation.

[0031] The thickness of the substrate can be selected as appropriate, usually 10 to 300 μm, preferably 15 to 125 μm, and particularly preferably 20 to 80 μm.

[0032] The arithmetic mean roughness Ra of the substrate surface is preferably 2 to 50 nm, and particularly preferably 5 to 30 nm. Having the arithmetic mean roughness Ra of the substrate surface within this range makes it easier to impart the desired smoothness to the peel surface, thereby facilitating the formation of a ceramic green sheet with fewer pinholes and variations in thickness.

[0033] Furthermore, it is preferable that the substrate in this embodiment substantially does not contain microbubbles. Here, microbubbles refer to bubbles with a diameter of about 3 to 50 μm. By the substrate not containing such microbubbles, the thickness accuracy of the substrate can be increased, and the surface smoothness of the resulting release film can be further improved.

[0034] 2. Release Agent Layer In this embodiment, the release agent layer is not particularly limited in composition, etc., as long as the maximum release force and surface free energy described above can be achieved. From the viewpoint of making it easier to achieve the maximum release force and surface free energy described above, the release agent layer in this embodiment is preferably a cured product of a release agent composition containing an active energy ray curable component and a silicone-based component. Note that the mass ratios in the description of compositions such as the release agent composition are based on the active ingredient (solid content), and solvents are not included unless otherwise specified.

[0035] (1) Active Energy Ray Curable Component The active energy ray curable component is not particularly limited as long as it is a component that hardens when irradiated with active energy rays, and may be, for example, a monomer, oligomer or polymer, or a mixture thereof. The active energy ray curable component is preferably a (meth)acrylic acid ester. If the main component of the release agent layer is a cured product of a (meth)acrylic acid ester component, the aforementioned surface free energy can be more easily achieved in the release agent layer. In this specification, (meth)acrylic acid ester means both acrylic acid ester and methacrylic acid ester. The same applies to other similar terms.

[0036] The (meth)acrylic acid ester is preferably at least one selected from polyfunctional (meth)acrylate monomers and (meth)acrylate oligomers, and more preferably at least one selected from trifunctional or higher (meth)acrylate monomers and (meth)acrylate oligomers, and even more preferably trifunctional or higher (meth)acrylate monomers, and particularly preferably pentafunctional or higher (meth)acrylate monomers. Having trifunctional or higher functions results in excellent curability of the release agent composition, and also better peelability of the surface of the resulting release agent layer, making it easier to reduce the maximum peeling force mentioned above.

[0037] Examples of the polyfunctional (meth)acrylate monomer include 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, neopentyl glycol adipate di(meth)acrylate, neopentyl glycol hydroxypivalate di(meth)acrylate, dicyclopentanyl di(meth)acrylate, caprolactone-modified dicyclopentenyl di(meth)acrylate, ethylene oxide-modified phosphoric acid di(meth)acrylate, allylated cyclohexyl di(meth)acrylate, isocyanurate di(meth)acrylate, trimethylolpropane tri(meth)acrylate, dipentaerythritol tri(meth)acrylate, dipentaerythritol tetra(meth)acrylate, propionic acid-modified dipentaerythritol tri(meth)acrylate, pentaerythritol tri(meth)acrylate, propylene oxide-modified trimethylolpropane tri(meth)acrylate, tris((meth)acryloxyethyl)isocyanurate, propionic acid-modified dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, caprolactone-modified dipentaerythritol hexa(meth)acrylate, etc. Among them, dipentaerythritol hexa(meth)acrylate is preferable. These may be used alone or in combination of two or more kinds. <> <>

[0038] Examples of the polyfunctional (meth)acrylate oligomer include polyester acrylate oligomers, epoxy acrylate oligomers, urethane acrylate oligomers, polyether acrylate oligomers, polybutadiene acrylate oligomers, silicone acrylate oligomers, etc. <> <>

[0039] Polyester acrylate oligomers can be obtained, for example, by esterifying the hydroxyl groups of polyester oligomers having hydroxyl groups at both ends, which are obtained by condensation of polyvalent carboxylic acids and polyhydric alcohols, with (meth)acrylic acid, or by esterifying the terminal hydroxyl groups of oligomers obtained by adding alkylene oxide to polyvalent carboxylic acids with (meth)acrylic acid.

[0040] Epoxy acrylate oligomers can be obtained, for example, by reacting (meth)acrylic acid with the oxirane ring of relatively low molecular weight bisphenol type epoxy resins or novolak type epoxy resins for esterification. Also, carboxyl-modified epoxy acrylate oligomers obtained by partially modifying epoxy acrylate oligomers with dibasic carboxylic acid anhydrides can also be used.

[0041] Urethane acrylate oligomers can be obtained, for example, by esterifying polyurethane oligomers obtained by the reaction of polyether polyols or polyester polyols and polyisocyanates with (meth)acrylic acid.

[0042] Polyether acrylate oligomers can be obtained by esterifying the hydroxyl groups of polyether polyols with (meth)acrylic acid.

[0043] The above polyfunctional (meth)acrylate monomers and polyfunctional (meth)acrylate oligomers can be used individually or in combination of two or more. Also, a combination of polyfunctional (meth)acrylate monomers and polyfunctional (meth)acrylate oligomers can be used.

[0044] In the release agent composition, the active energy ray curable component may be used alone or in combination of two or more.

[0045] The amount of active energy ray curable component in the release agent composition is preferably 80 to 99 parts by mass, more preferably 85 to 98 parts by mass, and particularly preferably 90 to 97 parts by mass, per 100 parts by mass of the release agent composition. By satisfying these conditions for the amount of active energy ray curable component, the maximum release force and surface free energy mentioned above can be more easily achieved in the release agent layer.

[0046] (2) Silicone-based component The silicone-based component is not particularly limited as long as it can impart the desired peelability to the peeling surface, and polyorganosiloxane, preferably polyorganosiloxane having a reactive functional group, and particularly preferably polydimethylsiloxane having a reactive functional group is used. When polyorganosiloxane having a reactive functional group is used, the reactive functional group reacts by irradiation with active energy rays or by a separate reaction step (e.g., a heating step), and the polyorganosiloxane (silicone-based component) is incorporated into the crosslinked structure formed by the other peeling agent composition and fixed. This suppresses the transfer of the silicone-based component in the peeling agent layer to the ceramic green sheet molded on the peeling agent layer. Furthermore, from the viewpoint of making it easier to achieve the maximum peeling force mentioned above, it is more preferable to use a non-aqueous silicone-based component with relatively low polarity than a water-based silicone-based component with relatively high polarity (easily soluble in water and easy to add to water-containing compositions).

[0047] The reactive functional group may be introduced at one end of the polyorganosiloxane, at both ends, or in the side chain. Examples of reactive functional groups include (meth)acryloyl groups, vinyl groups, maleimide groups, epoxy groups, carboxyl groups, isocyanate groups, and hydroxyl groups. Among these, (meth)acryloyl groups, vinyl groups, and maleimide groups are preferred as they can be cured simultaneously with the curing of the active energy ray-curable component (during active energy ray irradiation). It is preferable that at least two of these reactive functional groups are introduced into one molecule of polyorganosiloxane. Furthermore, two or more types of these reactive functional groups may be introduced into one molecule of polyorganosiloxane.

[0048] Furthermore, in the release agent composition, one type of silicone component may be used alone, or two or more types may be used in combination.

[0049] The amount of silicone-based components in the release agent composition is preferably 0.25 to 5 parts by mass, more preferably 0.5 to 3.5 parts by mass, and particularly preferably 1.0 to 2.5 parts by mass, per 100 parts by mass of the release agent composition. When the amount of silicone-based components satisfies these conditions, it becomes easier to achieve the maximum release force mentioned above. In particular, when the amount of silicone-based components is 0.25 parts by mass or more, the release film is more likely to exhibit good release performance. Furthermore, when the amount of silicone-based components is 5 parts by mass or less, it becomes easier to achieve the surface free energy mentioned above.

[0050] Furthermore, the total mass ratio of the active energy ray curable component and the silicone-based component to the total mass in the release agent composition is preferably 85% by mass or more, more preferably 90% by mass or more, and particularly preferably 95% by mass or more. Having the total mass ratio of the active energy ray curable component and the silicone-based component within the above range makes the surface of the formed release agent layer highly smooth, making it easier to achieve the aforementioned maximum release force and surface free energy, and making it easier to obtain sufficient curability of the release agent composition.

[0051] (3) When ultraviolet light is used as the active energy ray to irradiate the photopolymerization initiator release agent composition, it is preferable that the release agent composition further contains a photopolymerization initiator. By including a photopolymerization initiator in this way, the active energy ray curable component (and silicone-based component) can be cured efficiently, and the polymerization curing time and the amount of light irradiation can be reduced. Furthermore, by adjusting the photopolymerization initiator, the aforementioned maximum release force can be more easily achieved, and the pre-heat release force and minimum release force described later can also be easily adjusted to desired values.

[0052] Examples of photopolymerization initiators include benzophenone, acetophenone, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, benzoin benzoic acid, benzoin methyl benzoate, benzoin dimethyl ketal, 2,4-diethylthioxanthone, 1-hydroxycyclohexyl phenyl ketone, benzyl diphenyl sulfide, tetramethylthiuram monosulfide, azobisisobutyronitrile, benzyl, dibenzyl, diacetyl, β-chloranthraquinone, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, and 2-benzothiazole-N,N-diethyldithiocarbamate. In particular, 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, 2-benzyl-2-(dimethylamino)-4'-morpholinobyrophenone, and 2-hydroxy-1-{4-[4-(2-hydroxy-2-methylpropionyl)benzyl]phenyl}-2-methylpropan-1-one are preferred, as they are said to have excellent surface hardening properties. Among these, 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, 2-benzyl-2-(dimethylamino)-4'-morpholinobyrophenone, and 2-hydroxy-1-{4-[4-(2-hydroxy-2-methylpropionyl)benzyl]phenyl}-2-methylpropan-1-one are especially preferred from the viewpoint of making it easier to achieve the maximum peeling force mentioned above. These can be used individually or in combination of two or more types.

[0053] The amount of photopolymerization initiator added is preferably in the range of 1 to 20 parts by mass, 2 to 14 parts by mass, and particularly 3 to 9 parts by mass, per 100 parts by mass of the release agent composition.

[0054] (4) Other components The release agent layer may contain silica, antistatic agents, dyes, pigments and other additives as needed. These additives are preferably used in an amount of 10 parts by mass or less, more preferably 5 parts by mass or less, and particularly preferably 2 parts by mass or less, per 100 parts by mass of the release agent composition.

[0055] (5) Thickness of the release agent layer The thickness of the release agent layer is preferably 0.3 to 2 μm, and particularly preferably 0.5 to 1.5 μm. A thickness of 0.3 μm or more in the release agent layer makes it easier to improve the smoothness of the surface of the release agent layer, making it easier to suppress the occurrence of pinholes and thickness variations in the ceramic green sheet, and making it easier to achieve the maximum release force mentioned above. Furthermore, a thickness of 2 μm or less in the release agent layer makes it easier to reduce the hardening shrinkage of the release agent layer, making it easier to suppress the occurrence of curling of the release film. In addition, it makes it easier to suppress blocking of the release film when the release film is wound into a roll, reducing the occurrence of winding defects, and also reduces the amount of static charge during unwinding, making it easier to suppress the adhesion of foreign matter.

[0056] 3. Method for Manufacturing the Release Film The release film according to this embodiment can be manufactured by conventionally known methods. For example, the release agent composition described above or a coating solution obtained by diluting the release agent composition with an organic solvent can be applied to one side of a substrate, and then the resulting coating film can be dried as needed and cured by irradiation with active energy rays to form a release agent layer and obtain a release film. Isopropyl alcohol, methyl ethyl ketone, and the like can be used as appropriate organic solvents.

[0057] If the reactive functional groups of the silicone-based components are heat-activated, the reaction can be induced by heating during the drying of the coating film, thereby incorporating the silicone-based components into the cross-linked structure.

[0058] Methods for applying the release agent solution include, for example, gravure coating, bar coating, spray coating, spin coating, knife coating, roll coating, and die coating.

[0059] As the active energy rays, ultraviolet rays, electron beams, etc. are usually used. The irradiation amount of the active energy rays varies depending on the type of energy rays. For example, in the case of ultraviolet rays, the light quantity is preferably 50 to 1000 mJ / cm ２ is preferable, and particularly 100 to 500 mJ / cm ２ is preferable. In the case of electron beams, about 0.1 to 50 kGy is preferable.

[0060] 4. Physical properties of the release film The release film according to this embodiment satisfies the above-described condition of the maximum peeling force, but it is also preferable to satisfy the following conditions regarding the peeling force.

[0061] First, regarding the laminate of the peeling force measurement sheet and the release film produced in the same manner as described above, when the peeling force when peeling the peeling force measurement sheet from the release film under each temperature condition from 70 °C to 100 °C is measured, the peeling force specified as the minimum value is defined as the "minimum peeling force".

[0062] Moreover, for the release film according to this embodiment, it is preferable that the minimum peeling force is 90 mN / 40 mm or less, particularly preferably 70 mN / 40 mm or less, and more preferably 50 mN / 40 mm or less. When the minimum peeling force is 90 mN / 40 mm or less, it becomes easier to achieve the above-described maximum peeling force. On the other hand, regarding the lower limit value of the minimum peeling force, from the viewpoint of easily suppressing the target such as a ceramic green sheet from floating or peeling off from the release film unintentionally, it is preferably 10 mN / 40 mm or more, particularly preferably 14 mN / 40 mm or more, and more preferably 18 mN / 40 mm or more. The details of the measurement method of the minimum peeling force are as described in the test example described later.

[0063] Further, regarding the laminate of the peeling force measurement sheet and the release film produced in the same manner as described above, the peeling force measured when peeling the peeling force measurement sheet from the release film under the temperature condition of 23 °C is defined as the "peeling force before heating".

[0064] Furthermore, the release film according to this embodiment preferably has a pre-heating release force of 10 mN / 40 mm or more, particularly preferably 14 mN / 40 mm or more, and even more preferably 18 mN / 40 mm or more. A pre-heating release force of 10 mN / 40 mm or more makes it easier to suppress the unintended shifting or peeling of objects such as ceramic green sheets from the release film. On the other hand, the upper limit of the pre-heating release force is not particularly limited, but it is preferably 65 mN / 40 mm or less, particularly preferably 45 mN / 40 mm or less, and even more preferably 35 mN / 40 mm or less. A pre-heating release force of 65 mN / 40 mm or less makes it easier to achieve the maximum release force mentioned above. Details of the method for measuring the pre-heating release force are as described in the test examples below.

[0065] Furthermore, the release film according to this embodiment preferably has an absolute difference of 35 mN / 40 mm or less between the maximum release force and the release force before heating, more preferably 20 mN / 40 mm or less, particularly preferably 10 mN / 40 mm or less, and even more preferably 5 mN / 40 mm or less. Being within this range allows for good release properties to be achieved even when using an unheated jig, thus broadening the applications of the release film according to this embodiment. The lower limit of the absolute value of the difference is not particularly limited; for example, it may be greater than 0 mN / 40 mm, particularly 1 mN / 40 mm or more, and even more preferably 2 mN / 40 mm or more.

[0066] Furthermore, the difference obtained by subtracting the minimum peeling force from the maximum peeling force of the release film according to this embodiment is preferably 20 mN / 40 mm or less, more preferably 10 mN / 40 mm or less, particularly preferably 5 mN / 40 mm or less, and even more preferably 3 mN / 40 mm or less. Being within this range makes it easier to consistently achieve good peelability even when the degree of heating of the jig fluctuates, and the release film according to this embodiment has a wide range of applications. The lower limit of the above difference is not particularly limited, and may be greater than 0 mN / 40 mm, particularly 1 mN / 40 mm or more, and even more preferably 2 mN / 40 mm or more.

[0067] Furthermore, in the release film according to this embodiment, it is preferable that the pre-heating release force described above is generally constant within the release surface. Specifically, when the pre-heating release force is measured at any 10 points within the release surface and the average, maximum, and minimum values ​​are calculated and determined, it is preferable that the maximum value is less than 1.1 times the average value and the minimum value is less than 0.9 times the average value. When the release film according to this embodiment satisfies these conditions, the unevenness of the release force is reduced, and stable release becomes easier.

[0068] In the release film according to this embodiment, the arithmetic mean height Sa, which is an indicator of smoothness on the surface of the release agent layer opposite to the substrate, is preferably less than 10 nm, particularly preferably 8 nm or less, and even more preferably 5 nm or less. Having an arithmetic mean height Sa of less than 10 nm makes it easier to suppress the occurrence of pinholes when applying ceramic slurry to the release surface, thereby suppressing the occurrence of pinholes and thickness variations in the molded ceramic green sheet and reducing the defect rate. Details of the method for measuring the arithmetic mean height Sa are described in the test examples below.

[0069] 5. Method of Use of the Release Film The release film according to this embodiment can be used as an ordinary release film, but it is particularly suitable for use in the ceramic green sheet manufacturing process. As described above, the release film according to this embodiment can peel off ceramic green sheets well even when peeling them off using a heated jig. For this reason, the release film according to this embodiment is particularly suitable for use in the ceramic green sheet manufacturing process, which involves a step of peeling off ceramic green sheets using a heated jig. Here, the temperature of the heated jig may be, for example, 70°C or higher, and particularly 80°C or higher. Also, the temperature may be 100°C or lower, and particularly 90°C or lower.

[0070] In particular, the release film according to this embodiment is preferably used in the following method for manufacturing a ceramic green sheet. Specifically, it is preferable to use it in a method that includes forming a ceramic green sheet on the release agent layer side of the release film according to this embodiment, and peeling the ceramic green sheet from the release film using a jig heated to a temperature of 70°C or higher and 100°C or lower.

[0071] In the above method, known means and techniques can be used for forming the ceramic green sheet, printing the electrodes, selecting the jigs to be used, and peeling off the ceramic green sheet.

[0072] The embodiments described above are provided to facilitate understanding of the present invention and are not intended to limit it. Accordingly, 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.

[0073] For example, other layers may be provided between the substrate and the release agent layer, or on the surface of the substrate opposite to the release agent layer.

[0074] The present invention will be described in more detail below with reference to examples, but the scope of the present invention is not limited to these examples.

[0075] [Example 1] (1) Preparation of the substrate A polyethylene terephthalate (PET) film (31 μm thick) with the same roughness on both sides was prepared as the substrate. The arithmetic mean roughness (Ra) on both sides of this PET film was 29 nm, and the maximum protrusion height (Rp) was 257 nm. These arithmetic mean roughness (Ra) and maximum protrusion height (Rp) were measured using the method described later.

[0076] (2) Preparation of the release agent composition Dipentaerythritol hexaacrylate (manufactured by Shin Nakamura Kogyo Co., Ltd., product name "A-DPH", solid content 100% by mass) 99.0 parts by mass (solid content equivalent, the same applies hereinafter) as an active energy ray curable component, polyether-modified acryloyl group-containing polydimethylsiloxane (low polarity silicone component for non-aqueous systems, manufactured by Big Chemie, product name "BYK-3510") 2.0 parts by mass as a silicone component, and 2-hydroxy-1-{4-[4-(2-hydroxy-2-methylpropionyl)benzyl]phenyl}-2-methylpropan-1-one (IGM Resins) as a photopolymerization initiator 5.0 parts by mass of B.V. Co.'s product "Omnirad 127D" was mixed in a mixture of isopropyl alcohol and methyl ethyl ketone (mixture ratio 3:1) to obtain a coating solution of the stripping agent composition (solid content concentration 20% by mass).

[0077] (3) Formation of the release agent layer The release agent composition solution obtained in step (2) was applied to one side of the substrate prepared in step (1) using a bar coater, and the resulting coating film was dried at 80°C for 1 minute. Then, the dried coating film was subjected to an integrated light intensity of 500 mJ / cm². ２ The material was cured by irradiating it with ultraviolet light under the specified conditions. This resulted in a release film in which a release agent layer (thickness: 0.97 μm) was formed on one side of the substrate (thickness: 31 mm). The thickness of the release agent layer was measured using the method described later.

[0078] (4) Various Measurements The arithmetic mean roughness (Ra) and maximum protrusion height (Rp) of the PET film described above were measured as follows. The PET film was fixed to the glass plate using double-sided tape so that the side opposite to the side to be measured was facing the glass plate. Then, the surface to be measured was measured using a surface roughness measuring instrument (Mitutoyo Corporation, product name "SV-3000S4", stylus type) in accordance with JIS B0601-1994 to measure the arithmetic mean roughness (Ra; nm) and maximum protrusion height (Rp; nm).

[0079] The thickness of the release agent layer described above was measured as follows: After cutting the obtained release film to 100 mm x 100 mm, the release film was placed in a reflective film thickness gauge (Filmetrix, product name "F20") with the substrate side facing the suction stage. The film thickness was measured at 10 locations on the release agent layer side, and the average value was taken as the thickness of the release agent layer (μm).

[0080] [Examples 2-4, Comparative Example 2] Release films were obtained in the same manner as in Example 1, except that the amount of silicone-based components, the cumulative amount of ultraviolet light, and the thickness of the release agent layer were changed as shown in Table 1.

[0081] [Comparative Example 1] A coating solution of a release agent composition (solid content concentration 30% by mass) was obtained by mixing 90 parts by mass (on a solid content basis, the same applies hereinafter) of methylated melamine resin (manufactured by Nippon Carbide Co., Ltd., product name "MW-30"), 5.0 parts by mass of terminally carbinol-modified polydimethylsiloxane as a polyorganosiloxane (manufactured by Shin-Etsu Chemical Co., Ltd., product name "KF-6000", mass average molecular weight: 6000), and 5.0 parts by mass of p-toluenesulfonic acid as an acid catalyst in a mixed solvent of isopropyl alcohol and isobutyl alcohol (mass ratio 4:1).

[0082] The obtained coating solution was uniformly applied to one side of a biaxially oriented polyethylene terephthalate film (thickness: 38 μm) used as a substrate by a bar coater. Next, it was heated and dried at 120°C for 1 minute to cure the release agent composition. As a result, a release film was obtained in which a release agent layer (thickness: 1.0 μm) was formed on one side of the substrate (thickness: 38 mm). The thickness of the release agent layer was measured by the method described above.

[0083] [Comparative Example 3] A coating solution of a release agent composition (solid content concentration 30% by mass) was obtained by mixing 95 parts by mass (on a solid content basis, the same applies hereinafter) of a curable silicone resin (manufactured by Shin-Etsu Chemical Co., Ltd., product name "KS-5508") and 5.0 parts by mass of a thermosetting agent (manufactured by Shin-Etsu Chemical Co., Ltd., product name "PL-500") in a mixed solvent of isopropyl alcohol and isobutyl alcohol (mass ratio 4:1).

[0084] The obtained coating solution was uniformly applied to one side of the same substrate used in Example 1 using a bar coater. Next, it was heated and dried at 120°C for 1 minute to cure the release agent composition. As a result, a release film was obtained in which a release agent layer (thickness: 1.0 μm) was formed on one side of the substrate (thickness: 31 mm). The thickness of the release agent layer was measured using the method described above.

[0085] [Test Example 1] (Measurement of Peeling Force) (1) Preparation of Sample for Measurement Barium titanate powder (BaTiO) ３ A coating solution for peeling force measurement was prepared by mixing and dispersing 100 parts by mass of (product name "BT-03" manufactured by Sakai Chemical Industry Co., Ltd.), 8 parts by mass of polyvinyl butyral resin (product name "Eslec B-KBM-2" manufactured by Sekisui Chemical Co., Ltd.) as a binder, and 4 parts by mass of dioctyl phthalate (product name "Dioctyl Phthalate Grade 1" manufactured by Kanto Chemical Co., Ltd.) as a plasticizer in 135 parts by mass of a mixture of glycol monomethyl ether and toluene (mass ratio 50:50) using a ball mill.

[0086] The obtained coating solution for measuring peeling force was applied to the peeling surface of the peeling films obtained in the examples and comparative examples, and dried at 105°C for 60 seconds. This resulted in obtaining a measurement sample comprising a peeling film and a 3 μm thick peeling force measuring sheet formed on the peeling surface of the peeling film.

[0087] (2) Measurement of pre-heating peel force The sample for measurement obtained in step (1) above was cut to a width of 40 mm and left to stand for one day at 23°C and 50% R.H. Thereafter, at 23°C and 50% R.H., the sheet for measuring the peel force was peeled from the release film using a tensile testing machine at a peel angle of 90° and a peel speed of 0.3 m / min, and the force required to peel (peel force; unit: mN / 40 mm) was measured. The measurement length was set to 70 mm, and the measurement values ​​for the first 10 mm and the last 10 mm were excluded from the valid values. The average of these measurement values ​​was taken as the peel force, and this peel force measurement was performed three times, with the average value being taken as the pre-heating peel force. The results are shown in Table 1.

[0088] (3) Measurement of Maximum and Minimum Peel Force The sample obtained in step (1) above was cut to a width of 40 mm and left to stand for one day at 23°C and 50% R.H. Then, it was placed on a heated suction stand set to 70°C so that the side of the sample facing the release film was in contact with the suction stand, and after standing for about 15 seconds, when the temperature of the sheet for measuring the peel force reached 70°C by measuring the temperature with a thermal camera, the sheet for measuring the peel force was peeled from the release film using a tensile testing machine at a peel angle of 90° and a peel speed of 0.3 m / min, and the force required to peel (peel force; unit: mN / 40 mm) was measured. The measurement length was set to 70 mm, and the measurement values ​​for the first 10 mm and the last 10 mm were excluded from the valid values. The average of these measurement values ​​was taken as the peel force, and this peel force measurement was performed three times, and the average value was taken as the peel force at 70°C.

[0089] Next, the peeling force was measured in the same manner as above, except that the set temperature of the heated suction platform and the temperature at which peeling occurred, as measured by the thermal camera, were set to 71°C, and the peeling force at 71°C was obtained. Furthermore, the temperature was increased by 1°C increments up to 100°C, from 72°C to 73°C, and the peeling force at each of these temperatures was obtained.

[0090] Of the peeling forces obtained at temperatures from 70°C to 100°C in 1°C increments, the maximum value was defined as the maximum peeling force, and the minimum value as the minimum peeling force. These are shown in Table 1.

[0091] In all examples and comparative examples, the minimum value was the peeling force specifically measured at a set temperature of 70°C, and the maximum value was the peeling force specifically measured at a set temperature of 100°C.

[0092] (4) Calculation of the difference in peeling force Using the peeling force before heating, the maximum peeling force, and the minimum peeling force measured in steps (2) and (3) above, the difference between the two types of peeling forces was calculated using the following two formulas. The results are shown in Table 1. Difference between maximum peeling force and minimum peeling force = Maximum peeling force - Minimum peeling force Difference between maximum peeling force and peeling force before heating (absolute value) = |Maximum peeling force - Peeling force before heating|

[0093] [Test Example 2] (Measurement of Surface Roughness) The release surfaces of the release films obtained in the Examples and Comparative Examples were observed using a scanning white-light interference microscope (Hitachi High-Tech Science Co., Ltd., product name "VS-1550") under the following conditions: measurement magnification: 50x, measurement area: 251 × 251 μm, height difference: ±150 nm, and the arithmetic mean height Sa (μm) was measured. The results are shown in Table 1.

[0094] [Test Example 3] (Evaluation of Peelability) The measurement sample obtained in the same manner as in step (1) of Test Example 1 was cut to a size of 100 mm x 100 mm and then left to stand for one day at 23°C and 50% R.H.

[0095] Subsequently, under conditions of 23°C and 50% R.H., the sample for measurement was placed on a non-heated suction platform so that the release film side of the sample was in contact with the platform and fixed in place. Next, a plate-shaped suction jig (heatable, capable of adsorbing flat surfaces, size: 100 mm x 100 mm) was heated to 70°C and attached to the ceramic green sheet side of the sample for measurement. Three seconds after attachment, the sheet for measuring the peeling force was peeled from the release film at a peeling speed of 0.3 m / min, and the condition of the ceramic green sheet at that time was observed.

[0096] Furthermore, the set temperature of the adsorption jig was changed to 80°C, 90°C, and 100°C, and the peeling and the condition of the ceramic green sheet were checked at each temperature.

[0097] The peelability was then evaluated based on the following criteria. The results are shown in Table 1. A: At all temperatures of 70°C, 80°C, 90°C, and 100°C, the ceramic green sheet could be peeled off without cracking. B: At at least one of the temperatures of 70°C, 80°C, 90°C, and 100°C, minor cracks of 2 mm or less were observed in the ceramic green sheet, but other than these cracks, there were no problems with the use of the ceramic green sheet. C: At at least one of the temperatures of 70°C, 80°C, 90°C, and 100°C, cracks exceeding 2 mm were observed in the ceramic green sheet.

[0098] [Test Example 4] (Measurement of Surface Free Energy) For the release films obtained in the examples and comparative examples, the contact angles of various droplets with respect to the release surface of the release agent layer were measured, and based on these values, the surface free energy (mJ / m) was calculated using the Kitazaki-Hata theory. ２ The contact angle was determined using a contact angle meter (Kyowa Interface Science Co., Ltd., product name "DM-701") and measured by the static droplet method in accordance with JIS R3257. For the droplets, diiodomethane was used as the "dispersion component," 1-bromonaphthalene as the "dipole component," and distilled water as the "hydrogen bonding component." Other conditions were as follows. The results are shown in Table 1. Measurement environment: 23°C, 50% RH Droplet volume: 2 μL Time from dropping to measurement: 3 seconds The average value of measurements taken at 6 locations using each liquid was adopted as the average value of the contact angle, and the surface free energy was calculated and adopted using this average value of the contact angle.

[0099] [Test Example 5] (Evaluation of Slurry Coatability) The coating solution for measuring peeling force was applied to the peeling surface in the same manner as in step (1) of Test Example 1 above. The coating condition at that time was evaluated based on the following criteria. A: No visible repellency was observed at the edges of the coating, and a good coated surface was obtained. Or, slight repellency (less than 0.5 mm) was observed, but it was not a problem for the use of the ceramic green sheet. B: Repellency of 0.5 mm or more was observed at the edges of the coating.

[0100]

[0101] As can be seen from Table 1, the release film obtained in the examples was able to coat the ceramic green sheet slurry well, and the ceramic green sheet could be peeled off well even when a heated jig was used.

[0102] The release film of the present invention can be suitably used in the process of manufacturing ceramic green sheets.

Claims

1. A release film comprising a base material and a release agent layer provided on one side of the base material, wherein a release force measuring sheet with a thickness of 3 μm is formed on the side of the release agent layer opposite to the base material using a coating solution for release force measurement containing 100 parts by mass of barium titanate, 8 parts by mass of polyvinyl butyral resin, and 4 parts by mass of dioctyl phthalate, and the release film is obtained by measuring the release force when the release force measuring sheet is peeled from the release film under various temperature conditions from 70°C to 100°C, the maximum release force that can be identified as the maximum value is less than 100 mN / 40 mm, and the surface free energy on the side of the release agent layer opposite to the base material is 23 mN / m ２ A release film characterized by the above.

2. The release film according to claim 1, characterized in that the maximum peeling force is 10 mN / 40 mm or more.

3. The release film according to claim 1, characterized in that the pre-heating release force measured when the release force measuring sheet is peeled off the release film under a temperature of 23°C is 10 mN / 40 mm or more.

4. The release film according to claim 3, characterized in that the absolute value of the difference between the maximum release force and the release force before heating is 35 mN / 40 mm or less.

5. The release film according to claim 1, characterized in that, when the peeling force is measured when the peeling force measuring sheet is peeled from the release film under various temperature conditions from 70°C to 100°C for the laminate, and the minimum value of the peeling force identified is defined as the minimum peeling force, the difference obtained by subtracting the minimum peeling force from the maximum peeling force is 20 mN / 40 mm or less.

6. The release film according to claim 1, characterized in that the arithmetic mean height Sa on the side of the release agent layer opposite to the substrate is less than 10 nm.

7. The release film according to claim 1, characterized in that the release agent layer is a cured product of a release agent composition containing an active energy ray curable component and a silicone-based component.

8. The release film according to claim 1, characterized in that it is for use in the manufacturing process of ceramic green sheets.

9. A method for manufacturing a ceramic green sheet, comprising forming a ceramic green sheet on the surface of the release agent layer of the release film according to claim 1, and peeling the ceramic green sheet from the release film using a jig heated to a temperature of 70°C or higher and 100°C or lower.

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