CN-122029220-A - Polyester film

Abstract

The invention provides a polyester film which can improve the peeling property in the process of peeling ceramic green sheets from a release film and can also inhibit uneven coating and wrinkling. A polyester film having an elastic deformation power of one surface exceeding 55% and a shrinkage ratio in the machine and transverse directions of 2.8% or less after heat treatment at 150 ℃ for 5 minutes.

Inventors

• NAKAGAWA YOHEI
• Hayakawa touraku

Assignees

• 三菱化学株式会社

Dates

Publication Date

20260512

Application Date

20241220

Priority Date

20231221

Claims (20)

1. 1. A polyester film, wherein, The elastic deformation power of one surface exceeds 55%, and the shrinkage in the machine direction and the transverse direction after heat treatment at 150 ℃ for 5 minutes is 2.8% or less.
2. 2. The polyester film according to claim 1, wherein, The shrinkage in the transverse direction after heat treatment at 150 ℃ for 5 minutes is 1.5% or less.
3. 3. The polyester film according to claim 1 or 2, wherein, The one surface satisfies the following (1) and (2), (1) The arithmetic mean height Sa is 15nm or less, (2) The maximum peak height Sp is less than 150 nm.
4. 4. The polyester film according to any one of claims 1 to 3, comprising particles, wherein the content of the particles is 250ppm to 10000ppm by mass relative to a layer comprising the particles.
5. 5. The polyester film according to any one of claims 1 to 4, comprising particles having an average particle diameter of 1 μm or less.
6. 6. The polyester film according to any one of claims 1 to 5, comprising particles having a mohs hardness of 9 or less.
7. 7. The polyester film according to any one of claims 1 to 6, comprising particles comprising at least particles (a 1) and particles (a 2), wherein the particles (a 1) are alumina particles and the particles (a 2) are particles other than the particles (a 1).
8. 8. The polyester film according to any one of claim 1 to 7, wherein, The layer forming the one surface contains particles including at least particles (a 1) and particles (a 2), and Zeta potentials of the particles (a 1) and (a 2) at pH7 are positive values of the particles (a 1) and negative values of the particles (a 2), or negative values of the particles (a 1) and positive values of the particles (a 2).
9. 9. The polyester film according to claim 8, wherein, The content of the particles having a positive Zeta potential at pH7 is 50ppm to 5000ppm by mass relative to the layer forming the one surface.
10. 10. The polyester film according to claim 8 or 9, wherein, The content of the particles having a Zeta potential of a negative value at pH7 is 100ppm to 8000ppm by mass relative to the layer forming the one surface.
11. 11. The polyester film according to any one of claim 8 to 10, wherein, The particles having a Zeta potential of positive value at pH7 are alumina particles.
12. 12. The polyester film according to any one of claims 8 to 11, wherein, The particles having a Zeta potential of negative value at pH7 are silica or organic particles.
13. 13. The polyester film according to any one of claim 1 to 12, wherein, The layer forming the one surface contains particles, and the ratio of the content of particles having a mohs hardness of 8 or less to the content of all particles contained in the layer forming the one surface, i.e., the content of particles having a mohs hardness of 8 or less/the content of all particles, is 0.6 to 0.95 by mass ratio.
14. 14. The polyester film according to any one of claim 1 to 13, wherein, The layer forming the one surface contains particles whose main component is particles having a mohs hardness of 8 or less, and the content of the particles having a mohs hardness of 8 or less is less than 1800ppm in terms of mass ratio with respect to the layer forming the one surface.
15. 15. The polyester film according to claim 3, wherein, The maximum peak height Sp of the above-mentioned (2) is 100nm or less.
16. 16. The polyester film according to any one of claims 1 to 15, wherein, The degree of plane orientation DeltaP is 165 or more.
17. 17. The polyester film according to any one of claims 1 to 16, wherein, The ratio of the arithmetic mean height Sa of one surface to the arithmetic mean height Sa of the other surface, i.e., the arithmetic mean height Sa of the other surface/the arithmetic mean height Sa of one surface is 2 or more and 18 or less, wherein the arithmetic mean height Sa of the other surface > the arithmetic mean height Sa of the one surface.
18. 18. The polyester film according to any one of claims 1 to 17, which is composed of at least two layers.
19. 19. The polyester film according to any one of claims 1 to 18, which is composed of three layers.
20. 20. The polyester film according to claim 18 or 19, comprising particles whose content is 250ppm or more and 2800ppm or less in mass ratio with respect to one surface layer.

Description

Polyester film Technical Field The present invention relates to a polyester film. More specifically, the present invention relates to a polyester film used as a support for ceramic green sheets in a process for producing a laminated ceramic capacitor, for example. Background Polyester films represented by polyethylene terephthalate films and polyethylene naphthalate films have excellent properties such as mechanical properties, dimensional stability, flatness, heat resistance, chemical resistance, optical properties, and the like, and are used for various applications, for example, in interlayer insulating resin release substrates, dry film resist substrates, release films for Ceramic green sheets constituting multilayer Ceramic capacitors (MLCCs), and the like, utilizing the smoothness of film surfaces. In the production process of the laminated ceramic capacitor, a release film having a release layer is first produced by coating and drying a release agent or the like on a polyester film, and a ceramic slurry containing a ceramic component such as barium titanate and a binder resin is coated and dried on the release film, and then an electrode is printed and dried by a screen printing method or the like to produce an electrode-printed ceramic green sheet. Then, the obtained ceramic green sheet was cut into a predetermined shape, the ceramic green sheet was peeled from the release film, and the peeled ceramic green sheets were laminated in a plurality of layers and integrated, and then each of the chips was cut, and the internal electrode and the dielectric layer were sintered in a firing furnace, thereby manufacturing a laminated ceramic capacitor. In recent years, with the electrification of automobiles, the high functionality of smartphones, and the like, miniaturization and high capacity of laminated ceramic capacitors have been demanded. In response to the above-mentioned demand, intensive studies have been made on thinning of ceramic green sheets, but if thinning of ceramic green sheets progresses, there is a concern that peeling failure such as breakage may occur in the step of peeling ceramic green sheets from a release film. Patent document 1 discloses a release film for a ceramic green sheet production process comprising a release agent layer provided on one side of a polyester substrate, wherein the elastic deformation power is 45% or more in a load displacement curve measured when a load of 20mN is applied to the release agent layer side using a micro surface hardness tester, from the viewpoint of improving the releasability of the ceramic green sheet. Prior art literature Patent literature Patent document 1 Japanese patent application laid-open No. 2022-144248 Disclosure of Invention Problems to be solved by the invention Further miniaturization and higher capacity of the laminated ceramic capacitor are expected to progress in the future, and further thinning of the ceramic green sheet is demanded. If the ceramic green sheet is further thinned, the concern of occurrence of peeling failure such as breakage in the step of peeling the ceramic green sheet from the release film is higher than in the past. In addition, heat treatment for drying the ceramic slurry applied to the release film may cause heat shrinkage of the release film, and uneven application, wrinkles, and the like may occur. Therefore, it is required to improve the peelability of the release film and to suppress the occurrence of coating unevenness, wrinkles, and the like. However, as a result of repeated studies by the present inventors, it has been found that, for example, a predetermined filler (particle) or the like is blended in a release film from the viewpoint of facilitating the release of a ceramic green sheet from the release film, but if the releasability is improved as described above, coating unevenness, wrinkles or the like tend to occur in a heat treatment step in a manufacturing process of a laminated ceramic capacitor, and therefore it is difficult to highly satisfy both. Solution for solving the problem The first embodiment of the present invention has been made in view of the above-described circumstances, and provides a polyester film which can improve the peelability in a step of peeling a ceramic green sheet from a release film, and can suppress the occurrence of coating unevenness and wrinkles. The present inventors have repeatedly studied in view of the above-mentioned circumstances, and as a result, have found that the above-mentioned problems can be solved by using a specific polyester film. That is, the present inventors have found that the above problems can be solved by using a specific polyester film obtained by adjusting the composition, average particle diameter, particle size distribution, hardness, affinity with polyester, the type of polyester, and the conditions for film formation, for example, when particles are blended. That is, the present invention provides the following as one embodiment. [I-