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CN-117980143-B - Biaxially oriented polyester film

CN117980143BCN 117980143 BCN117980143 BCN 117980143BCN-117980143-B

Abstract

Disclosed is a biaxially oriented polyester film having a smooth release surface, which has a highly smooth surface on both surfaces, thereby suppressing transfer roughness of the release layer due to the surface shape after winding into a roll. In a biaxially oriented polyester film, among the values of the maximum protrusion heights in each field of view obtained by the following method, the values of the maximum protrusion heights belonging to the first 5% are respectively denoted as Sp5% A (nm) and Sp5% B (nm), sp5% A is 110 or less, and Sp5% B is 150 or more and 1000 or less. A scanning white interference microscope VertScan is used to measure the surface image of a field of view of 561 μm square in 100 fields of view using a 10-fold objective lens, and the maximum protrusion height Sp value in each field of view is obtained, and the value belonging to the first 5% of these SP values is taken as the Sp5% value.

Inventors

  • Chiyo Mihiro
  • Dong Daluzhuosi

Assignees

  • 东丽株式会社

Dates

Publication Date
20260512
Application Date
20220906
Priority Date
20210924

Claims (15)

  1. 1.A biaxially oriented polyester film having a surface satisfying the following condition (1), namely, A-side, and a surface opposite to the A-side, namely, B-side, satisfying the following condition (2), In the condition (1), the A surface has a protrusion, and when the value of the maximum protrusion height belonging to the first 5% of the values of the maximum protrusion heights in each field of view obtained by the following method is Sp5% A, sp5% A is 110nm or less, In the condition (2), the surface B has protrusions, and when the value of the maximum protrusion height belonging to the first 5% of the values of the maximum protrusion heights in each field of view obtained by the following method is Sp5% B, sp5% B is 150nm to 1000nm, The maximum protrusion height measurement method comprises the following steps: Using a scanning white interference microscope VertScan, a surface image of a field of view of 561 μm square was measured in 100 fields of view using a 10-fold objective lens, the maximum protrusion height Sp value in each field of view was obtained, and among these Sp values, the value belonging to the first 5% was regarded as Sp5%, When the layer having the B-plane is referred to as a P2 layer, the thickness of the P2 layer is referred to as T P2 , and the maximum particle diameter of particles contained in the P2 layer is referred to as D P2 , T P2 /D P2 is 1 to 5 inclusive, and the units of T P2 and D P2 are μm.
  2. 2. The biaxially oriented polyester film according to claim 1, wherein protrusions are present on the surface of the a-plane, and N 80nm a is 0.4/mm 2 or less when the number of protrusions having a height of 80nm or more is N 80nm a.
  3. 3. The biaxially oriented polyester film according to claim 2, wherein protrusions are present on the surface of the a-plane, and N 10nm a is 300/mm 2 or more and 1000/mm 2 or less, when the number of protrusions having a height of 10nm or more is N 10nm a.
  4. 4. The biaxially oriented polyester film according to any one of claims 1 to 3, which has a layer comprising a polyester resin as a main component, namely, a P1 layer, wherein the surface of the P1 layer is the outermost surface of the biaxially oriented polyester film, and wherein the P1 layer has the a-plane.
  5. 5. The biaxially oriented polyester film according to claim 4, wherein T P1 is 2 μm or more and 10 μm or less, assuming that the thickness of the P1 layer is T P1 .
  6. 6. The biaxially oriented polyester film according to claim 4, wherein the P1 layer contains particles, T P1 /D P1 is 20 to 100 inclusive, and the unit of D P1 is μm, when the maximum particle diameter of the particles contained in the P1 layer is D P1 .
  7. 7. The biaxially oriented polyester film according to claim 1, wherein CaR is 100 ° or more and 120 ° or less in the case where the water contact angle of the a-plane is CaR °.
  8. 8. The biaxially oriented polyester film according to claim 7, which has a layer comprising a polyester resin as a main component, namely a P1 layer and a coating layer, namely an R1 layer, wherein the R1 layer is provided on the P1 layer, the surface of the R1 layer is the outermost surface of the biaxially oriented polyester film, and the R1 layer has the a-plane.
  9. 9. The biaxially oriented polyester film according to claim 8, wherein the R1 layer contains at least any one of a silicone resin, a long-chain alkyl resin and an acrylic resin as a main component.
  10. 10. The biaxially oriented polyester film according to claim 8, wherein T R1 is 0.01 μm or more and 1.00 μm or less, assuming that the thickness of the R1 layer is T R1 .
  11. 11. The biaxially oriented polyester film according to claim 4, which has a structure of at least 3 or more layers including a P3 layer containing particles between the P1 layer and the P2 layer.
  12. 12. The biaxially oriented polyester film according to any one of claims 1 to 3, wherein the P2 layer contains 2 or more kinds of particles having different average particle diameters.
  13. 13. A biaxially oriented polyester film according to any one of claims 1 to 3, wherein the film thickness is measured in the film width direction, that is, in the same direction as the film roll width direction, and when the average film thickness is represented by T AVE , the maximum film thickness is represented by T MAX , and the minimum film thickness is represented by T MIN , the thickness unevenness DeltaT represented by the following formula (1) is 5.0% or less, the units of T AVE 、T MAX and T MIN are μm, Δt (%) =100× (T MAX -T MIN ）/T AVE . Formula (1).
  14. 14. The biaxially oriented polyester film according to any one of claims 1 to 3, wherein the static friction coefficient between the a-side and the B-side is 0.8 or less.
  15. 15. The biaxially oriented polyester film according to any one of claims 1 to 3, which is used as a support film for green sheet molding in a process for producing a laminated ceramic capacitor.

Description

Biaxially oriented polyester film Technical Field The present invention relates to a biaxially oriented polyester film having surfaces having specific characteristics on both surfaces of the film. Background Thermoplastic resins are used in various industrial fields because of their good processability. Further, products obtained by processing these thermoplastic resins into films have an important role in the present life such as industrial applications, optical products, packaging applications, and magnetic recording tape applications. In recent years, in electronic information devices, miniaturization, and high integration have been advanced, and along with this, improvement in processability has been demanded for process films used in the manufacturing process of electronic information devices. As a process film for manufacturing electronic components, there is an increasing demand for a process film for releasing a green sheet, particularly for use in a process for manufacturing a laminated ceramic capacitor, which has been remarkably developed in recent years. The green sheet is a thin-film ceramic obtained by applying a ceramic slurry to a release film and drying the same, and in the release process, the surface smoothness of the release film is important. This is because, when the concave-convex shape of the release surface is transferred to the surface of the green sheet, a defect due to the concave-convex shape occurs in the subsequent step of stacking the green sheets. However, the surface of the release layer is roughened by propagation of the uneven shape on the surface of the base film, and the surface shape of the surface opposite to the release surface is transferred to the release surface when the base film is wound into a roll, so that it is difficult to maintain the surface smoothness. In particular, since the thickness of the green sheet for the new generation is reduced to 0.5 μm, it is necessary to maintain smoothness on the release surface before and after winding into a roll. In order to solve such problems, for example, patent document 1 discloses a method of controlling the particle size of a film to control the surface roughness of both surfaces and thereby suppress the transfer of irregularities to a green sheet. Prior art literature Patent literature Patent document 1 Japanese patent application laid-open No. 2015-208939 Disclosure of Invention Problems to be solved by the invention However, in patent document 1, the content of particles is high, which is insufficient for the application to the new generation. The present invention aims to provide a biaxially oriented polyester film which is excellent in not only coatability and peelability when a green sheet is formed by laminating a sheet with a release resin coating layer interposed therebetween, but also in surface defects and sheet breakage caused by transfer of a concave-convex shape to the green sheet, and which is excellent in process conveyability (surface damage defect, suppression of surface scratch) and winding property (winding wrinkles and winding dislocation) by controlling the particle size and lamination thickness of particles contained in the film, and which can maintain the above-mentioned surface smoothness even when a recycled resin raw material is used as a film raw material. Means for solving the problems In order to solve the above problems, the present invention adopts the following configuration. That is to say, [I] a biaxially oriented polyester film having a surface (A-side) satisfying the following condition (1), and a surface (B-side) opposite to the A-side satisfying the following condition (2). In the condition (1), the A surface has protrusions, and when the value of the maximum protrusion height belonging to the first 5% of the values of the maximum protrusion heights in each field of view obtained by the following method is Sp5% A (nm), sp5% A is 110 or less. In the condition (2), the surface B has protrusions, and when the value of the maximum protrusion height belonging to the first 5% of the values of the maximum protrusion heights in each field of view obtained by the following method is Sp5% B (nm), sp5% B is 150 to 1000. (Method for measuring maximum protrusion height) Using a scanning white interference microscope VertScan, a surface image of a field of view of 561 μm square was measured in 100 fields of view using a 10-fold objective lens, and the maximum protrusion height Sp value in each field of view was obtained, and among these Sp values, the value belonging to the first 5% was set as Sp 5%. The biaxially oriented polyester film according to [ II ], wherein protrusions are present on the surface of the A-plane, and N 80nm A is 0.4 or less when the number of protrusions having a height of 80nm or more is N 80nm A (number/mm 2). The biaxially oriented polyester film according to [ I ] or [ II ], wherein protrusions are present on the surface of the A-plane, and N 10nm A is 300 to 100