CN-121986025-A - Biaxially oriented polyester film

Abstract

A biaxially oriented polyester film for dry film resist support use, which has a laminated structure of 2 or more layers, wherein at least 1 layer contains an inorganic compound containing a germanium element, an organic salt containing a sulfur element and an organic salt containing a phosphorus element, the atomic content of the germanium element is 10 to 30 ppm by weight, the atomic content of the sulfur element is 1 to 25 ppm by weight, the atomic content of the phosphorus element is 25 to 37 ppm by weight, and the atomic content of the metal elements is 1 to 25 ppm by weight in total, based on the weight of the polyester film. A polyester film having a small number of foreign matters and good film forming properties is provided.

Inventors

• AHN JAEHO
• Kaihara Shun
• KANEKO YUSUKE
• FUJIWARA TAKASHI

Assignees

• 东丽株式会社

Dates

Publication Date

20260505

Application Date

20240925

Priority Date

20230927

Claims (5)

1. 1. A biaxially oriented polyester film for dry film resist support use, which has a laminated structure of 2 or more layers, wherein at least 1 layer contains an inorganic compound containing a germanium element, an organic salt containing a sulfur element and an organic salt containing a phosphorus element, the atomic content of the germanium element is 8 to 30 ppm by weight, the atomic content of the sulfur element is 3 to 25 ppm by weight, the atomic content of the phosphorus element is 20 to 40 ppm by weight, and the atomic content of the metal elements is 10 to 30 ppm by weight in total, based on the weight of the polyester film.
2. 2. The biaxially oriented polyester film according to claim 1, wherein the polyester resin composition constituting the polyester film has a melt specific resistance of 3.5X10 6 . OMEGA..about.cm or less.
3. 3. The biaxially oriented polyester film according to claim 1 or 2, wherein the following (1) and (2) are satisfied; (1) When the content of the metal element relative to the entire polyester resin composition constituting the polyester film is set to M mol/t, M satisfies the following formula 1: m is more than or equal to 0.0 and less than or equal to 1.0 (1) (2) When the content of phosphorus element relative to the entire polyester resin composition constituting the polyester film is set to P mol/t, M-P satisfies the following formula 2: -1.0≤M-P≤0.0 (formula 2).
4. 4. The biaxially oriented polyester film according to claim 1 or 2, wherein when a region of 7.5mm in the longitudinal direction and 1.1mm in the width direction is observed with a white light source of an optical microscope, the number of coarse foreign matters having a length of 1 μm or more is 20 pieces/cm 2 or less, and when a region of 7.5mm in the longitudinal direction and 1.1mm in the width direction is observed with a polarized light source, the number of gelled matters having a length of 1 μm or more is 2 pieces/cm 2 or less.
5. 5. The biaxially oriented polyester film for dry film resist support according to claim 1, wherein when the thickness unevenness of 2000m in the longitudinal direction of the film is measured, the variation in the thickness unevenness is 6.0% or less on average.

Description

Biaxially oriented polyester film Technical Field The present invention relates to biaxially oriented polyester films. Background Dry film resists (hereinafter sometimes referred to as DFR) are used to form circuits for printed wiring boards, semiconductor packages, flexible substrates, and the like. The dry film resist has a structure in which a photosensitive layer (photoresist layer) is laminated on a polyester film as a support and then sandwiched by protective films (cover films) formed of a polyethylene film, a polypropylene film, a polyester film, or the like. In order to manufacture a conductor circuit using the dry film resist, the following steps are generally performed. (1) And a step of peeling the protective film from the dry film resist and laminating the protective film with the substrate seed conductive base material layer so that the surface of the exposed resist layer is closely adhered to the surface of the conductive base material layer such as copper foil on the substrate. (2) Next, a photomask on which a conductor circuit pattern is burned is placed on a support made of a polyester film, and ultraviolet rays are irradiated from the photomask onto a resist layer mainly made of a photosensitive resin, thereby exposing the resist layer to light. (3) And a step of removing unreacted components in the resist layer by dissolving the photomask and the polyester film in a solvent. (4) Then, etching is performed with an acid or the like to dissolve and remove the exposed portion of the conductive base material layer. After the step (4), the photoreactive portion in the resist layer remains as it is with the conductive base material layer portion corresponding to the photoreactive portion, and then the conductor circuit on the substrate is formed through the step of removing the remaining resist layer. Therefore, a polyester film as a support is required to be capable of transmitting ultraviolet rays efficiently. In this way, the conductor circuit pattern is accurately reflected on the resist layer. In particular, in recent years, along with miniaturization, weight saving, and the like of IT equipment and the like, miniaturization and high density of printed wiring boards have been demanded, and formation of fine patterns having a wiring width or a wiring pitch of about 5 μm has been demanded, and a polyester film for dry film resist supports capable of achieving high resolution has been demanded. When forming fine patterns with a wiring width or a wiring interval of about 5 μm, coarse objects of about 1 μm cause defects in the resist. Examples of the coarse material include particles applied to the base film, and agglomerates of metals such as antimony or magnesium contained in the polyester resin composition, which form bubbles (voids) during stretching. If the voids containing the agglomerates are present, ultraviolet rays irradiated in the exposure step scatter, and the resist is not cured in a pattern. In order to prevent aggregation of metallic foreign matters contained in the polyester resin composition, the voids are reduced, and the content of metallic elements such as magnesium element or lithium element in the polyester resin composition is reduced, with the result that the yield in the film manufacturing process is lowered. In particular, in the electrostatic casting method in which a high voltage is applied to a polyester resin composition in a molten state so as to adhere the composition in a sheet form to a cooled drum, the adhesion force between the sheet and the cooled drum is reduced, the film thickness uniformity or transparency is reduced, and a problem that defects occur on the film surface due to uneven application is remarkably generated, and therefore, it is also necessary to achieve the requirement of improving productivity (electrostatic applicability). Patent documents 1 and 2 propose a method of adding an alkali metal compound, an alkaline earth metal compound, and a phosphorus compound in large amounts to a polyester as a method of improving electrostatic applicability. However, although this method can improve the electrostatic applicability to some extent, since magnesium acetate is used in large amounts, metallic foreign matters are generated, and problems of exposure blocking occur during ultraviolet irradiation in the exposure step. Patent document 3 proposes a method of adjusting lithium compounds and alkaline earth metal compounds contained in respective polyester resin compositions in a layer having a film surface and a layer not having a surface to have good electrostatic applicability and to suppress irregularities generated on the resist pattern wall surface, but fine antimony metal foreign matters or magnesium metal foreign matters are still generated on the surface exposed to ultraviolet rays, so that it is difficult to form fine patterns having a wiring width or a wiring interval of 5 μm or less by the above method. Patent document 4 proposes a method o