Electromagnetic wave absorber, article with electromagnetic wave absorber, and method for manufacturing electromagnetic wave absorber

Patent metadata

Field	Value
Publication number	US-11266048-B2
Application number	US-201816957885-A
Country	US
Kind code	B2
Filing date	Dec 28, 2018
Priority date	Dec 28, 2017
Publication date	Mar 1, 2022
Grant date	Mar 1, 2022

Abstract

An electromagnetic wave absorber (1a) includes a resistive layer (10), an electrically conductive layer (20) and a dielectric layer (30). The electrically conductive layer (20) has a sheet resistance lower than a sheet resistance of the resistive layer (10). The dielectric layer (30) is disposed between the resistive layer (10) and the electrically conductive layer (20). The electromagnetic wave absorber (1a) has a first slit (15). The first slit (15) extends, in the resistive layer (10), from a first principal surface (10a) distal to the dielectric layer (30) toward the dielectric layer (30) in a direction perpendicular to the first principal surface (10a) and divides the resistive layer (10) into a plurality of first blocks (17). Each of the first blocks (17) has a minimum dimension (D1) of 2 mm or more at the first principal surface (10a).

First claim

The invention claimed is:

1. An electromagnetic wave absorber comprising:
a resistive layer;
an electrically conductive layer having a sheet resistance lower than a sheet resistance of the resistive layer; and
a dielectric layer disposed between the resistive layer and the electrically conductive layer, wherein
the electromagnetic wave absorber has at least one of a first slit and a second slit,
the first slit extends, in the resistive layer, from a first principal surface distal to the dielectric layer toward the dielectric layer in a direction perpendicular to the first principal surface and divides the resistive layer into a plurality of first blocks,
the second slit extends, in the electrically conductive layer, from a second principal surface distal to the dielectric layer toward the dielectric layer in a direction perpendicular to the second principal surface and divides the electrically conductive layer into a plurality of second blocks,
each of the first blocks has a minimum dimension of 2 mm or more at the first principal surface
each of the second blocks has a minimum dimension of 1 mm or more at the second principal surface,
the electromagnetic wave absorber is a λ/4 electromagnetic wave absorber, and
the electromagnetic wave absorber satisfies at least one of the following conditions (I), (II) and (III),
(I) the electromagnetic wave absorber has the second slit, and
when the second principal surface is level, an area of the plurality of second blocks at the second principal surface is 90% or more of a sum of the area of the plurality of second blocks and an area of an opening of the second slit,
(II) the electromagnetic wave absorber has a plurality of the first slits,
the plurality of the first slits include a first slit group composed of a plurality of the first slits parallel to each other at the first principal surface,
the minimum dimension of the first blocks at the first principal surface is 20 mm or less, and
the plurality of the first slits include a second slit group composed of a plurality of the first slits that are parallel to each other at the first principal surface and that intersect the plurality of the first slits included in the first slit group,
(III) the electromagnetic wave absorber has a plurality of the second slits,
the plurality of the second slits include a third slit group composed of a plurality of the second slits parallel to each other at the second principal surface,
the minimum dimension of the second blocks at the second principal surface is 20 mm or less, and
the plurality of the second slits include a fourth slit group composed of a plurality of the second slits that are parallel to each other at the second principal surface and that intersect the plurality of the second slits included in the third slit group.

2. The electromagnetic wave absorber according to claim 1 , wherein
the electromagnetic wave absorber has the second slit, and
when the second principal surface is level, the area of the plurality of second blocks at the second principal surface is 90% or more of the sum of the area of the plurality of second blocks and the area of the opening of the second slit.

3. The electromagnetic wave absorber according to claim 1 , wherein
the electromagnetic wave absorber has the plurality of the first slits,
the plurality of the first slits include the first slit group composed of the plurality of the first slits parallel to each other at the first principal surface, and
the minimum dimension of the first blocks at the first principal surface is 20 mm or less.

4. The electromagnetic wave absorber according to claim 3 , wherein the plurality of the first slits include the second slit group composed of the plurality of the first slits that are parallel to each other at the first principal surface and that intersect the plurality of the first slits included in the first slit group.

5. The electromagnetic wave absorber according to claim 1 , wherein
the electromagnetic wave absorber has the plurality of the second slits,
the plurality of the second slits include the third slit group composed of the plurality of the second slits parallel to each other at the second principal surface, and
the minimum dimension of the second blocks at the second principal surface is 20 mm or less.

6. The electromagnetic wave absorber according to claim 5 , wherein the plurality of the second slits include the fourth slit group composed of the plurality of the second slits that are parallel to each other at the second principal surface and that intersect the plurality of the second slits included in the third slit group.

7. The electromagnetic wave absorber according to claim 1 , wherein the resistive layer has a sheet resistance of 120 to 800 Ω/□.

8. An article with an electromagnetic wave absorber, comprising:
an article having a curved face or a corner; and
the electromagnetic wave absorber according to claim 1 that is adhered to the curved face or adhered to across the corner.

9. A method for manufacturing an electromagnetic wave absorber, comprising;
providing a resistive layer;
providing an electrically conductive layer having a sheet resistance lower than a sheet resistance of the resistive layer;
disposing a dielectric layer between the resistive layer and the electrically conductive layer; and
forming at least one of a first slit and a second slit, wherein
the first slit extends, in the resistive layer, from a first principal surface distal to the dielectric layer toward the dielectric layer in a direction perpendicular to the first principal surface and divides the resistive layer into a plurality of first blocks,
the second slit extends, in the electrically conductive layer, from a second principal surface distal to the dielectric layer toward the dielectric layer in a direction perpendicular to the second principal surface and divides the electrically conductive layer into a plurality of second blocks,
each of the first blocks has a minimum dimension of 2 mm or more at the first principal surface,
each of the second blocks has a minimum dimension of 1 mm or more at the second principal surface,
the electromagnetic wave absorber is a λ/4 electromagnetic wave absorber, and
the electromagnetic wave absorber satisfies at least one of the following conditions (I), (II) and (III),
(I) the electromagnetic wave absorber has the second slit, and
when the second principal surface is level, an area of the plurality of second blocks at the second principal surface is 90% or more of a sum of the area of the plurality of second blocks and an area of an opening of the second slit,
(II) the electromagnetic wave absorber has a plurality of the first slits,
the plurality of the first slits include a first slit group composed of a plurality of the first slits parallel to each other at the first principal surface,
the minimum dimension of the first blocks at the first principal surface is 20 mm or less, and
the plurality of the first slits include a second slit group composed of a plurality of the first slits that are parallel to each other at the first principal surface and that intersect the plurality of the first slits included in the first slit group,
(III) the electromagnetic wave absorber has a plurality of the second slits,
the plurality of the second slits include a third slit group composed of a plurality of the second slits parallel to each other at the second principal surface,
the minimum dimension of the second blocks at the second principal surface is 20 mm or less, and
the plurality of the second slits include a fourth slit group composed of a plurality of the second slits that are parallel to each other at the second principal surface and

Assignees

• Nitto Denko Corp

Inventors

• Yamagata Kazuto
• Machinaga Hironobu
• Ukei Hiroichi
• Ui Takehiro

Classifications

• B32B27/304

  comprising vinyl halide (co)polymers, e.g. PVC, PVDC, PVF, PVDF · CPC title

• B32B2264/108

  Carbon, e.g. graphite particles · CPC title

• B32B15/18

  comprising iron or steel {(B32B15/011, B32B15/012 and B32B15/013 take precedence)} · CPC title

• B32B3/14

  characterised by a face layer formed of separate pieces of material {which are juxtaposed side-by-side (B32B5/02 takes precedence)} · CPC title

• B32B27/365

  comprising polycarbonates · CPC title