Insulation sheets


The D581/D581A insulation sheets are made by combining mica paper with silicone adhesive. They have excellent heat resistance and electrical insulation properties.
Furthermore, they are unique in a way that they cause very little smoke, odor or gas and the expansion of mica at high temperature.


  • (1) Cause hardly any smoke or odor when heated to high temperature.
  • (2) Cause hardly any deterioration of strength or insulation resistance after heating.
  • (3) Have excellent water-resistant properties, showing extremely high electrical insulation in high humidity atmosphere.
  • 4) High edge strength which provides excellent workability for winding heater wires, etc.
  • (5) Can perform die-cutting easily*, and curling work is also possible.
    *Die-cutting is possible up to a board thickness of 1.5 mm depending on the product shape.
    Please contact us for more details as some products may be difficult to process due to the shape.


  • (1) Heaters, heater elements, resistors, coil layers, etc.
  • (2) The D581A also has light blocking effect, and is used as a peripheral insulation part for a projector’s optical source.

In addition to supplying materials, we provide secondary processing, and can suggest a variety of shapes according to customer’s specification environment.
The D581A is used as various types of thermal insulation parts from electronics appliances to factory automation systems.
Also, we always have boards with various thickness in stock to mass-produce parts in a short period of time.

These products have obtained the UL94 V-0 standard, as well as UL thermal index 746B (D581: Electrical properties 750℃, mechanical properties 450℃, D581A: Electrical properties 760℃, mechanical properties 600℃. (UL File No.E58537)

Composition and standard dimensions

D581 D581A
Mica Mica paper based on uncalcined muscovite Mica paper based on phlogopite
Binder Silicone
Standard thickness (mm) 0.15 to 1.2
Width × length (mm) 1000×1100 / 1000×1200


D581 D581A
Nominal thickness mm 0.5 0.5
Apparent density kg/m3 2.1× 103 2.0× 103
Loss of mass by heating (550℃ × 2 hr) wt% 0.50 0.47
Flexural strength MPa 254 167
Tensile strength MPa 237 178
Insulation resistance Normal state 2000 or more 2000 or more
At high temperature 370 280
Dielectric breakdown strength kV/mm 28 30
Compressive strength MPa 386 269
Young's modulus GPa 74 61
Linear expansion coefficient 1/K 9 to 12 × 106 9 to 12 × 106
Thermal conductivity W/m·K 0.23 0.20
Arc resistance sec 420 or more 420 or more
Comparative tracking index (CTI) V 600 or more 600 or more
UL 94V-0

*Measured in compliance with JIS C 2116 and JIS K 6911.
*The above values are examples from tests, and are not guaranteed values.