Toray Lumirror C21 PET Film is a standard polyester film at a single thickness of 6 micron, and its datasheet is written for capacitors
At 6 micron, a film is thinner than most of the polyester in the rest of this range by a factor of three or more. Toray Lumirror C21 PET Film is described as a standard polyester film for capacitors, with excellent processability including metallizing and good dielectric properties.
Why Capacitors Want a Film This Thin
In a film capacitor, the polyester is the dielectric: a thin insulating layer between metal electrodes. Thinner film generally means more capacitance in the same volume, and a metallized film allows the electrode to be deposited directly on the surface (a general explanation, not from this datasheet). That is why the datasheet highlights metallizing and the dielectric properties together.
The Numbers the Datasheet Gives
- Thickness: 6 um
- Tensile strength: about 225 to 245 MPa depending on direction (ASTM D882)
- Elongation at break: about 160 to 170 percent (ASTM D882)
- Heat shrinkage at 150°C for 30 minutes: about 1.3 percent in MD and 0.1 percent in TD (ASTM D1204)
- UL746B RTI: 105°C electrical, 105°C mechanical
- Properties: transparent, flat face
Strength at this thickness is the reason the film can be handled at all. Note that MPa is force per unit area, so at 6 um the total load the film can carry is tiny, and tension control on the metallizing and winding lines matters. The low TD shrinkage helps keep the film flat through heat steps. RTI is a UL rating related to the temperature a material can withstand in long-term use.
How It Differs from Neighboring Grades
- Toray Lumirror F552 PET Film is the other very thin film in this range, at 4.5 and 5.7 um, but it is an adhesion promoted base for thermal transfer ribbon rather than a capacitor film.
- Toray Lumirror S10 PET Film is the general-purpose standard film, starting at 12 um and listed for electrical insulation. It shares the 105°C UL rating, but C21 is much thinner and aimed at metallized capacitor use.
- Toray Lumirror P52 PET Film is also pretreated for metallizing, at 12 um, but for packaging rather than capacitors.
What the Datasheet Does Not Say
- The values are typical data under specific test conditions and are not limiting specifications, as the datasheet itself notes.
- No dielectric numbers such as breakdown voltage, dissipation factor, or dielectric constant are given, even though the datasheet says the dielectric properties are good.
- No haze, surface roughness, surface tension, or thickness tolerance is listed. For capacitor work, surface roughness and thickness uniformity are generally important, so ask for them.
- Only 150°C shrinkage is given, and some figures here are approximate ranges. Please check the official datasheet for exact values.
Quick Answers
What thickness does the datasheet cover?
6 um only.
What is the listed application?
Capacitors.
Can I buy Toray Lumirror C21 PET Film from Jinlu Film?
Yes. Jinlu Film supplies Toray Lumirror C21 PET Film. If you prefer a comparable-specification alternative, including domestic options, we can offer those as well, together with datasheets and samples so you can test them on your own line.
More PET Film Guides
- Toray Lumirror S56 PET Film: a low shrinkage film for FBT and FPC
- Toray Lumirror E60 PET Film: a soft white film for D2T2 printers
- Toray Lumirror S28 PET Film: a high-grade S10 with a uniform surface
- Toray Lumirror X21 PET Film: an anti-static white film for displays
Sourcing Capacitor Film
Jinlu Film supplies Toray Lumirror C21 PET Film, along with comparable ultra-thin polyester film grades, including domestic alternatives, for capacitor and metallizing applications. Tell us your capacitor type, thickness, and the electrical data you need, and contact us for technical data, samples, or a factory quote.
Source: Toray’s publicly available Lumirror C21 technical data sheet (typical values). Please refer to the latest official version. Lumirror, Toray, and related names are trademarks of their respective owners. This article is an independent explanation for reference only.
