MULTILAYERED POLYESTER FILM

Abstract

A multilayered polyester film which comprises a polyester film and, disposed on at least one surface thereof, a layer X which has a contact angel HX(1) with water of 0-60°, wherein the layer X has a degree of crystallinity C(0) of 0-30%. HX(1): Contact angle at one second after water has come into contact with layer X. A polyester film having excellent recoverability is provided by disposing a layer X on at least one surface of a polyester film, the layer X having a regulated contact angle with water and a regulated degree of crystallinity.

Claims

1. A multilayered polyester film which comprises a polyester film and, disposed on at least one surface of the polyester film, a layer X which has a water contact angle HX(1) of 0° or higher and 60° or lower, wherein the layer X has a degree of crystallinity C(0) of 0% or more and 30% or less. HX(1): Contact angle at one second after water has come into contact with layer X

2. The multilayered polyester film according to claim 1, wherein the degree of crystallinity C (150) of the layer X after a heat treatment at 150° C. for 30 minutes is 0% or more and 30% or less.

3. The multilayered polyester film according to claim 1, wherein a ratio Ra/Xt of a surface roughness Ra (nm) of the polyester film on a side where the layer X is provided to a thickness Xt (nm) of the layer X is 0.001 or more and 1.0 or less.

4. The multilayered polyester film according to claim 1, wherein the layer X contains a resin having polyvinyl alcohol as a main chain structure.

5. The multilayered polyester film according to claim 1, further comprising: a layer Y having a water contact angle HY (1) of 80° or higher and 120° or lower on a surface of the layer X opposite to a surface in contact with the polyester film, wherein the water contact angles HY (1))(°) and HY (20))(°) of the layer Y of the film satisfy the following formula:
45≤|HY(1)−HY(20)|≤80 HY(1): Contact angle at one second after water has come into contact with layer Y HY(20): Contact angle at 20 seconds after water has come into contact with layer Y.

6. The multilayered polyester film according to claim 5, wherein the layer Y contains a resin having dimethylsiloxane as a main chain structure.

7. The multilayered polyester film according to claim 5, wherein a layer to be released is provided on a surface of the layer Y opposite to the surface in contact with the layer X, and the multilayered polyester film is used for release applications in which the layer to be released is released from the layer Y.

8. The multilayered polyester film according to claim 5, wherein a layer to be released is provided on a surface of the layer Y opposite to a surface in contact with the layer X, and the multilayered polyester film is used for applications in which the layer X and the layer Y are removed after the layer to be released is released from the layer Y.

9. The multilayered polyester film according to claim 5, wherein a layer to be released is provided on a surface of the layer Y opposite to a surface in contact with the layer X, and the multilayered polyester film is used for reuse of a polyester film obtained by peeling off the layer to be released from the layer Y and then further removing the layer X and the layer Y.

10. The multilayered polyester film according to claim 7, wherein the layer to be released is a ceramic green sheet containing barium titanate as a main component.

11. The multilayered polyester film according to claim 1, which is used as a release film in a multilayer ceramic capacitor (MLCC) producing process.

12. A multilayered polyester film including a polyester film and a layer Y, wherein water contact angles HY (1))(°) and HY (20))(°) in the layer Y satisfy the following formulas:
80≤HY(1)≤120,10≤|HY(1)−HY(20)|≤80 HY(1): Contact angle at one second after water has come into contact with layer Y HY(20): Contact angle at 20 seconds after water has come into contact with layer Y.

Description

EXAMPLES

[0077] Hereinafter, the present invention will be described by way of examples, but the present invention is not necessarily limited to these examples.

[0078] [Production of PET-1]

[0079] Terephthalic acid and ethylene glycol were polymerized by a known method using antimony trioxide and magnesium acetate tetrahydrate as catalysts to obtain melt-polymerized PET. The obtained melt-polymerized PET had a glass transition temperature of 81° C., a melting point of 255° C., an intrinsic viscosity of 0.65, and a terminal carboxyl group content of 20 eq./t.

[0080] [Production of Masterbatch (MB)-A]

[0081] 99 parts by mass of PET-1 and 10 parts by mass of a 10 mass % water slurry of crosslinked polystyrene particles (styrene-acrylate copolymer) having a particle diameter of 0.1 μm (1 part by mass as crosslinked polystyrene particles) were supplied, and vent holes were maintained at a reduced pressure of 1 kPa or less to remove moisture, thereby obtaining MB containing 1 weight % of crosslinked polystyrene particles. The glass transition temperature was 81° C., a melting point was 255° C., an intrinsic viscosity was 0.61, and a terminal carboxyl group content was 22 eq./t.

[0082] [Production of MB-B]

[0083] 99 parts by mass of PET-1 and 1 part by mass of calcium carbonate particles having a particle diameter of 1.0 μm were supplied, and the vent holes were maintained at a degree of reduced pressure of 1 kPa or less to remove moisture, thereby obtaining MB containing 1 mass % of the particles. The glass transition temperature was 81° C., a melting point was 255° C., an intrinsic viscosity was 0.61, and a terminal carboxyl group content was 22 eq./t.

[0084] [Production of PEN]

[0085] A transesterification reaction was performed from dimethyl 2,6-naphthalenedicarboxylate and ethylene glycol using manganese acetate as a catalyst. After completion of the transesterification reaction, PEN was obtained by a known method using antimony trioxide as a catalyst. In addition, 5 crystal alumina particles having a particle size of 0.1 μm were added so that the content of the 5 crystal alumina particles was 0.1 mass % during polymerization. The obtained PEN had a glass transition temperature of 124° C., a melting point of 265° C., an intrinsic viscosity of 0.62, and a terminal carboxyl group concentration of 25 eq./t.

[0086] [Preparation of Coating Agent A]

[0087] 100 parts by mass of an addition reaction type silicone resin release agent (trade name LTC 750 A manufactured by Dow Corning Toray Silicone Co., Ltd.), and 2 parts by mass of a platinum catalyst (trade name SRX 212 manufactured by Dow Corning Toray Silicone Co., Ltd.) were adjusted to a solid content of 5 mass % using toluene as a solvent to obtain a coating agent A.

[0088] [Preparation of Coating Agent B]

[0089] Polyvinyl alcohol “Poval 5-74” (saponification degree of 74, average degree of polymerization of 500) manufactured by Kuraray Co., Ltd. was dissolved in water so as to be 4 mass % to obtain a coating agent B.

[0090] [Preparation of Coating Agent C]

[0091] Polyvinyl alcohol “Poval LM-25” (saponification degree of 34, average degree of polymerization of 400) manufactured by Kuraray Co., Ltd. was dissolved in water so as to be 4 mass % to obtain a coating agent C.

[0092] [Production of Coating Agent D]

[0093] A polyvinyl alcohol “AYB8041W” (saponification degree of 88, average degree of polymerization of 300, 3 mol % of copolymerization amount of 1,2-ethanediol) manufactured by Mitsubishi Chemical Corporation was dissolved in water so as to be 4 mass % to obtain a coating agent D.

[0094] [Production of Coating Agent E]

[0095] A polyvinyl alcohol “OKS-8089” (saponification degree of 88, average degree of polymerization of 450, 6 mol % of copolymerization amount of 1,2-ethanediol) manufactured by Mitsubishi Chemical Corporation was dissolved in water so as to be 4 mass % to obtain a coating agent E.

[0096] [Preparation of Coating Agent F]

[0097] PVA having a saponification degree of 75, an average degree of polymerization of 500, and a copolymerization amount of 1,2-ethanediol of 6 mol % was prepared with reference to Patent Document Japanese Patent Laid-open Publication No. 2004-285143. The PVA was dissolved in water so as to be 4 mass % to obtain a coating agent F.

[0098] [Preparation of Coating Agent G]

[0099] Polyvinyl alcohol “ASP-05” (saponification degree of 88, average degree of polymerization of 500, 1 mol % sodium sulfonate copolymerization) manufactured by JAPAN VAM & POVAL CO., LTD. was dissolved in water so as to be 4 mass % to obtain a coating agent G.

[0100] [Preparation of Coating Agent H]

[0101] Polyvinyl alcohol “GL-05” (saponification degree of 88, average degree of polymerization of 500) manufactured by Mitsubishi Chemical Corporation was dissolved in water so as to be 4 mass % to obtain a coating agent H.

[0102] [Preparation of Coating Agent I]

[0103] Polyvinyl alcohol “NL-05” (saponification degree of 99, average degree of polymerization of 500) manufactured by Mitsubishi Chemical Corporation was dissolved in water so as to be 4 mass % to obtain a coating agent I.

[0104] [Preparation of Coating Agent J]

[0105] In GL-05, a binder polymer (Emulsion polymer of methyl methacrylate/ethyl acrylate/acrylonitrile/N-methylolmethacrylamide=45/45/5/5 (molar ratio) (emulsifier: anionic surfactant)) and a crosslinking agent (hexamethoxymelamine crosslinking agent) were adjusted so as to have a solid content blending ratio of 34/24/42, and dispersed in water so that a solid content concentration was 4 mass % to obtain a coating agent J.

[0106] [Preparation of Coating Agent K]

[0107] Polyvinyl alcohol “3266” (saponification degree of 88, average degree of polymerization of 200, 3 mol % sodium sulfonate copolymerization) manufactured by Mitsubishi Chemical Corporation was dissolved in water so as to be 4 mass % to obtain a coating agent K.

[0108] [Production of Coating Agent L]

[0109] A polyvinyl alcohol “OKS-1089” (saponification degree of 88, average degree of polymerization of 2500, 3 mol % of copolymerization amount of 1,2-ethanediol) manufactured by Mitsubishi Chemical Corporation was dissolved in water so as to be 4 mass % to obtain a coating agent L.

[0110] [Preparation of Coating Agent M]

[0111] Polyvinylpyrrolidone “KW-30” (average degree of polymerization of 30,000) manufactured by Nippon Shokubai Co., Ltd. was dissolved in water so as to be 4 mass % to obtain a coating agent L.

[0112] [Preparation of Dielectric Paste]

[0113] Glass beads having a number average particle size of 2 mm were added to 100 parts by weight of barium titanate (trade name HPBT-1 manufactured by Fuji Titanium Industry Co., Ltd.), 10 parts by mass of polyvinyl butyral (trade name BL-1 manufactured by Sekisui Chemical Co., Ltd.), 5 parts by mass of dibutyl phthalate and 60 parts by mass of toluene-ethanol (mass ratio 30:30), and the mixture was mixed and dispersed for 20 hours by a jet mill, and then filtered to prepare a paste-like dielectric paste.

[0114] [Preparation of Pressure-Sensitive Adhesive]

[0115] 97 parts by mass of butyl acrylate, 3 parts by mass of acrylic acid, 0.2 parts by mass of azobisisobutyronitrile as a polymerization initiator, and 233 parts by mass of ethyl acetate were added, then nitrogen gas was flowed, and nitrogen substitution was performed for about 1 hour while stirring. Thereafter, a flask was heated to 60° C. and reacted for 7 hours to obtain an acrylic polymer having a weight average molecular weight (Mw) of 1.1 million. In this acrylic polymer solution (with a solid content of 100 parts by mass), 0.8 parts by mass of trimethylolpropane tolylene diisocyanate (trade name: “Coronate L”, manufactured by Nippon Polyurethane Industry Co., Ltd.) as an isocyanate-based cross-linking agent and 0.1 parts by mass of a silane coupling agent (trade name: “KBM-403”, manufactured by Shin-Etsu Chemical Co., Ltd.) were added to prepare a pressure-sensitive adhesive composition containing acryl as a main component.

Example 1

[0116] 80 parts by mass of PET-1 and 20 parts by mass of MB-A were mixed, vacuum-dried at 160° C. for 2 hours, then charged into an extruder, melted at 280° C., and extruded onto a casting drum having a surface temperature of 25° C. through a die to prepare an unstretched sheet.

[0117] Subsequently, the sheet was preheated by a heated roll group, then stretched 3.8 times in the longitudinal direction (MD direction) at a temperature of 90° C., and then cooled by a roll group at a temperature of 25° C. to obtain a uniaxially stretched film. The coating agent B was applied to the obtained uniaxially stretched film by a bar coating method so that the coating thickness after drying was 100 nm, and subsequently the film was stretched 4.3 times in the width direction (TD direction) perpendicular to the longitudinal direction in a heating zone at a temperature of 100° C. in a tenter while both ends of the film were held by clips. Further, in a heat treatment zone of the tenter, the resulting film was heat-fixed at a temperature of 235° C. for 10 seconds. Then, after uniformly slow cooling in a cooling zone, the film was taken up to obtain a multilayered polyester film in which the layer X was multilayered. The properties of the obtained polyester film and layer X were as shown in Tables 1 and 2.

[0118] The coating agent A was applied on the surface of the layer X of the obtained multilayered polyester film opposite to a surface in contact with the polyester film by a gravure coating method so that a thickness of the layer Y was 0.1 μm to obtain a multilayered polyester film. The properties of the layer Y were as shown in Table 3.

[0119] The dielectric paste as a substance to be released was applied to the obtained multilayered polyester film by a die coating method so that the thickness after drying was 1.0 μm. Thereafter, the dielectric was released from the obtained multilayered body, and a release film roll for a step in which the substance to be released was released was obtained. The film roll was introduced into a water washing apparatus having an unwinding and winding device, and washed with water at 100° C. for 2 minutes under a tension of 30 N/m to recover the polyester film from which the layer X and the layer Y had been removed.

[0120] The water contact angle HX (1) and the degree of crystallinity C(0) of the layer X were in preferable ranges, and the water contact angle of the layer Y was also in preferable ranges. Therefore, the releasability of the substance to be released and the removability of the layer X and the layer Y were excellent, and the film reused according to the item K. had no problem in practical use (Table 3).

Examples 2 to 6

[0121] A multilayered polyester film was prepared in the same manner as in Example 1 except for using the coating agent C in Example 2, the coating agent D in Example 3, the coating agent E in Example 4, the coating agent F in Example 5, and the coating agent G in Example 6 as the layer X, and the layer X and the layer Y were removed to reuse the polyester film (Tables 1, 2, and 3).

[0122] In Example 2, since the saponification degree was slightly low, the degree of crystallinity C(0) of the layer X was low, but the solvent resistance was slightly low. Therefore, the contact angle HY (1) of the layer Y was slightly small, and the releasability of the substance to be released was slightly deteriorated, but was in a practically acceptable range.

[0123] In Examples 3 and 6, since the amount of the copolymerization component was small, the degree of crystallinity C(0) of the layer X was slightly large, but there was no problem in practical use in the releasability of the substance to be released, the removability of the layer X and the layer Y, and the reusability of the polyester film.

[0124] In Examples 4 and 5, the degree of crystallinity C (0) C (150) of the layer X was able to be suppressed to a small value, and as a result, excellent removability of the layer X and the layer Y and reusability of the polyester film were exhibited.

Example 7

[0125] A multilayered polyester film was prepared in the same manner as in Example 4 except that the polyester raw material used was PEN and the film production conditions were as shown in the table, the layer X and the layer Y were removed, and the polyester film was reused (Tables 1, 2, and 3). The degree of crystallinity C(0) C (150) of the layer X was able to be suppressed to a small value, and as a result, excellent removability of the layer X and the layer Y and reusability of the polyester film were exhibited.

Example 8

[0126] A multilayered polyester film was prepared in the same manner as in Example 4 except that the polyester raw materials used were 80 parts by mass of PET-1 and 20 parts by mass of MB-B, and the thickness of the layer X was changed as shown in the table, the layer X and the layer Y were removed, and the polyester film was reused (Tables 4, 5, and 6).

[0127] The surface roughness of the polyester film was large, and Ra/Xt was large. As a result, the contact angle HY (20) of the layer Y was slightly large, and the removability of the layer X and the layer Y and the reusability of the polyester film were slightly poor, but were in a practically acceptable range.

Example 9

[0128] A multilayered polyester film was prepared in the same manner as in Example 1 except for using the coating agent M as the layer X, the layer X and the layer Y were removed, and the polyester film was reused (Tables 4, 5, and 6). Although the degree of crystallinity C(0) of the layer X was low, polyvinylpyrrolidone had a nonpolar moiety, and therefore had high affinity for an organic solvent and slightly low solvent resistance. Therefore, the contact angle HY (1) of the layer Y was slightly small, and the releasability of the substance to be released was slightly deteriorated, but was in a practically acceptable range.

Example 10

[0129] In Example 5, a pressure-sensitive adhesive was used as a substance to be released, and was applied by a die coating method so that the thickness after drying was 10 μm. Thereafter, the pressure-sensitive adhesive was released from the obtained multilayered body, and a release film roll for a step in which the substance to be released was released was obtained. The film roll was introduced into a water washing apparatus having an unwinding and winding device, and washed with water at 100° C. for 2 minutes under a tension of 30 N/m to recover the polyester film from which the layer X and the layer Y had been removed (Tables 4,5, and 6).

[0130] The degrees of crystallinity C(0), C (150) of the layer X were able to be suppressed to small values, and as a result, excellent removability of the layer X and the layer Y and reusability of the polyester film were exhibited.

Comparative Examples 1 to 5

[0131] A multilayered polyester film was prepared in the same manner as in Example 1 except for using the coating agent H in Comparative Example 1, the coating agent I in Comparative Example 2, the coating agent J in Comparative Example 3, the coating agent K in Comparative Example 4, and the coating agent L in Comparative Example 5 as the layer X, and the layer X and the layer Y were removed to reuse the polyester film (Tables 4, 5, and 6).

[0132] In Comparative Example 1 in which PVA constituting the layer X did not have a copolymerization component, HX (1) and the degree of crystallinity C(0) were large, and the contact angle of the layer Y was not in a preferable range, so that removability of the layer X and the layer Y was poor. Thereafter, when the pulverized polyester film was melt-extruded according to the above-described item K., since the layer X and the layer Y were not able to be removed and remained, deterioration occurred in the extruder, and thereby it was not possible to form a sheet.

[0133] In Comparative Example 2 in which the saponification degree of PVA constituting the layer X was large, HX (1) and the degree of crystallinity C(0) were large, and the contact angle of the layer Y was not in a preferable range, so that removability of the layer X and the layer Y was poor. Thereafter, when the pulverized polyester film was melt-extruded according to the above-described item K., since the layer X and the layer Y were not able to be removed and remained, deterioration occurred in the extruder, and thereby it was not possible to form a sheet.

[0134] In Comparative Example 3 in which the content of PVA was small as a component constituting the layer X and further a resin having a crosslinking action with a binder was contained, HX (1) and the degree of crystallinity C(0) were large, and the contact angle of the layer Y was not in a preferable range, so that removability of the layer X and the layer Y was poor. Thereafter, when the pulverized polyester film was melt-extruded according to the above-described item K., since the layer X and the layer Y were not able to be removed and remained, deterioration occurred in the extruder, and thereby it was not possible to form a sheet.

[0135] In Comparative Example 4 in which the average degree of polymerization of PVA constituting the layer X was small, the degree of crystallinity C(0) was large, and the contact angle of the layer Y was not in a preferable range, so that removability of the layer X and the layer Y was poor. Thereafter, when the pulverized polyester film was melt-extruded according to the above-described item K., since the layer X and the layer Y were not able to be removed and remained, deterioration occurred in the extruder, and thereby it was not possible to form a sheet.

[0136] In Comparative Example 5 in which the average degree of polymerization of PVA constituting the layer X was large, HX (1) and the degree of crystallinity C(0) were large, and the contact angle of the layer Y was not in a preferable range, so that removability of the layer X and the layer Y was poor. Thereafter, when the pulverized polyester film was melt-extruded according to the above-described item K., since the layer X and the layer Y were not able to be removed and remained, deterioration occurred in the extruder, and thereby it was not possible to form a sheet.

TABLE-US-00001 TABLE 1 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Polyester Polyester PET PET PET PET PET PET PEN film IV 0.64 0.64 0.64 0.64 0.64 0.64 0.61 Production Longitudinal Temperature 90 90 90 90 90 90 120 conditions magnification (° C.) Magnification 3.8 3.8 3.8 3.8 3.8 3.8 3.8 Lateral Temperature 100 100 100 100 100 100 150 magnification (° C.) Magnification 4.3 4.3 4.3 4.3 4.3 4.3 3.8 Heat treatment 235 235 235 235 235 235 235 temperature (° C.) Surface roughness Ra (nm) 8 8 8 8 8 8 5 Thickness (μm) 30 30 30 30 30 30 30

TABLE-US-00002 TABLE 2 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Layer X Constituent component PVA PVA PVA PVA PVA PVA PVA Copolymerization component — — 1,2- 1,2- 1,2- Sodium 1,2- ethanediol ethanediol ethanediol sulfonate ethanediol Copolymerization amount (mol %) — — 3 6 6 1 6 Saponification degree 74 34 88 88 75 88 88 Average degree of polymerization 500 400 300 450 500 500 450 Thickness (Xt) (nm) 100 100 100 100 100 100 100 Water contact angle HX (1) (°) 60 60 40 40 35 40 40 Water contact angle HX (20) (°) 30 15 16 16 15 15 16 |HX (1)-HX (20)| 30 45 24 24 20 25 24 Degree of crystallinity C (0) (%) 24 0 24 3 1 20 3 Degree of crystallinity C (150) 38 0 40 5 1 24 5 (%) Ra/Xt 0.08 0.08 0.08 0.08 0.08 0.08 0.08

TABLE-US-00003 TABLE 3 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Layer Y Constituent component Poly- Poly- Poly- Poly- Poly- Poly- Poly- dimethyl dimethyl dimethyl dimethyl dimethyl dimethyl dimethyl siloxane siloxane siloxane siloxane siloxane siloxane siloxane Thickness (nm) 100 100 100 100 100 100 100 Water contact angle HY (1) (°) 100 80 105 105 105 105 105 Water contact angle HY (20) (°) 33 40 35 28 25 33 28 |HY(1)-HY(20)| 67 40 70 77 80 72 77 Release Substance to be released Barium Barium Barium Barium Barium Barium Barium film titanate titanate titanate titanate titanate titanate titanate Releasability of Releasing 30 58 30 30 30 30 30 substance to be force released (mN/50 mm) Determination A B A A A A A Removal Removal Washing Washing Washing Washing Washing Washing Washing of layer X method with water with water with water with water with water with water with water and layer Y Water contact 82 70 80 76 70 78 70 angle (°) after removal Determination B A B A A A A Reuse Reuse method Melt Melt Melt Melt Melt Melt Melt extrusion extrusion extrusion extrusion extrusion extrusion extrusion IV(R) 0.51 0.60 0.51 0.60 0.60 0.55 0.58 Determination B A B A A B A

TABLE-US-00004 TABLE 4 Comparative Comparative Comparative Example 8 Example 9 Example 1 Example 2 Example 3 Polyester Polyester PET PET PET PET PET film IV 0.64 0.64 0.65 0.65 0.65 Production Longitudinal Temperature 90 90 90 90 90 conditions magnification (° C.) Magnification 3.8 3.8 3.8 3.8 3.8 Lateral Temperature 100 100 100 100 100 magnification (° C.) Magnification 4.3 4.3 4.3 4.3 4.3 Heat treatment 235 235 235 235 235 temperature (° C.) Surface roughness Ra (nm) 43 8 8 8 8 Thickness (μm) 30 30 30 30 30 Comparative Comparative Example 4 Example 5 Example 10 Polyester Polyester PET PET PET film IV 0.65 0.65 0.64 Production Longitudinal Temperature 90 90 90 conditions magnification (° C.) Magnification 3.8 3.8 3.8 Lateral Temperature 100 100 100 magnification (° C.) Magnification 4.3 4.3 4.3 Heat treatment 235 235 235 temperature (° C.) Surface roughness Ra (nm) 8 8 8 Thickness (μm) 30 30 30

TABLE-US-00005 TABLE 5 Comparative Comparative Comparative Comparative Comparative Example 8 Example 9 Example 1 Example 2 Example 3 Example 4 Example 5 Example 10 Layer X Main constituent PVA PVP PVA PVA PVA/acryl PVA PVA PVA components Copolymerization 1,2- — — — — Sodium 1,2- 1,2- component ethanediol sulfonate ethanediol ethanediol Copolymerization 6 — — — — 3 3 6 amount (mol %) Saponification degree 88 — 88 99 88 88 88 75 Average degree of 450 30000 500 500 500 200 2500 500 polymerization Thickness (Xt) (nm) 50 100 100 100 100 100 100 100 Water contact angle 40 55 62 64 62 40 65 35 HX (1) (°) Water contact angle 30 23 57 63 58 39 65 15 HX (20) (°) |HY(1)-HY(20)| 10 22 5 1 4 1 0 20 Degree of 3 0 32 33 33 31 38 1 crystallinity C (0) (%) Degree of 5 0 37 45 33 31 44 1 crystallinity C (150) Ra/Xt 0.86 0.08 0.08 0.08 0.08 0.08 0.08 0.08

TABLE-US-00006 TABLE 6 Comparative Comparative Comparative Example 8 Example 9 Example 1 Example 2 Example 3 Layer Y Main constituent Polydimethyl Polydimethyl Polydimethyl Polydimethyl Polydimethyl components siloxane siloxane siloxane siloxane siloxane Thickness (nm) 100 100 100 100 100 Water contact angle 105 74 105 105 105 HY (1) (°) Water contact angle 85 40 100 100 98 HY (20) (°) |HY (1)-HY (20)| 20 40 5 5 7 Release Substance to be released Barium Barium Barium Barium Barium film titanate titanate titanate titanate titanate Releasability Releasing 30 61 30 30 30 of substance force to be released (mN/50 mm) Determination A B A A A Removal of Removal Washing Washing Washing Washing Washing layer X and method with water with water with water with water with water layer Y Water contact 85 70 95 95 95 angle (°) after removal Determination B A C C C Reuse Reuse method Melt Melt Melt Melt Melt extrusion extrusion extrusion extrusion extrusion IV 0.53 0.60 — — — Determination B A — — — Comparative Comparative Example 4 Example 5 Example 10 Layer Y Main constituent Polydimethyl Polydimethyl Polydimethyl components siloxane siloxane siloxane Thickness (nm) 100 100 100 Water contact angle 105 105 105 HY (1) (°) Water contact angle 97 100 25 HY (20) (°) |HY (1)-HY (20)| 8 5 80 Release Substance to be released Barium Barium Pressure- film titanate titanate sensitive adhesive Releasability Releasing 30 30 15 of substance force to be released (mN/50 mm) Determination A A A Removal of Removal Washing Washing Washing layer X and method with water with water with water layer Y Water contact 95 95 70 angle (°) after removal Determination C C A Reuse Reuse method Melt Melt Melt extrusion extrusion extrusion IV — — 0.60 Determination — — A

INDUSTRIAL APPLICABILITY

[0137] Since the multilayered polyester film of the present invention has a low degree of crystallinity of the layer X and is excellent in water absorbability, the layer Y multilayered in contact with the layer X is excellent in removability with water. When the layer Y of the present invention is made of a water-repellent material, the layer Y can be suitably used as a release film for a process for producing a multilayer ceramic capacitor (MLCC) including a dielectric paste as a substance to be released. In addition, since the polyester film can be easily recovered from the release film after being used in the MLCC production process, the polyester film can be easily reused as a raw material for melt film formation.