Iambda/4 TYPE RADIO WAVE ABSORBER

Abstract

The present invention aims to provide a /4 type radio wave absorber having excellent durability. Provided is a /4 type radio wave absorber including: a resistive film containing molybdenum; a resistive film; a dielectric layer; and a reflective layer, in the stated order.

Claims

1. A /4 type radio wave absorber comprising: a resistive film containing molybdenum; a dielectric layer; and a reflective layer, in the stated order.

2. The /4 type radio wave absorber according to claim 1, wherein the resistive film comprises a barrier layer on at least one surface.

3. The /4 type radio wave absorber according to claim 2, wherein the barrier layer has a thickness of 9 nm or less.

4. The /4 type radio wave absorber according to claim 2, wherein the barrier layer contains an oxide or nitride of silicon, titanium, and copper.

5. The /4 type radio wave absorber according to claim 1, wherein the resistive film further contains nickel and chromium.

6. The /4 type radio wave absorber according to claim 5, wherein the resistive film contains molybdenum in an amount of 5% by weight or more, nickel in an amount of 40% by weight or more, and chromium in an amount of 1% by weight or more.

7. The /4 type radio wave absorber according to claim 3, wherein the barrier layer contains an oxide or nitride of silicon, titanium, and copper.

8. The /4 type radio wave absorber according to claim 2, wherein the resistive film further contains nickel and chromium.

9. The /4 type radio wave absorber according to claim 3, wherein the resistive film further contains nickel and chromium.

10. The /4 type radio wave absorber according to claim 7, wherein the resistive film further contains nickel and chromium.

11. The /4 type radio wave absorber according to claim 4, wherein the resistive film further contains nickel and chromium.

12. The /4 type radio wave absorber according to claim 8, wherein the resistive film contains molybdenum in an amount of 5% by weight or more, nickel in an amount of 40% by weight or more, and chromium in an amount of 1% by weight or more.

13. The /4 type radio wave absorber according to claim 9, wherein the resistive film contains molybdenum in an amount of 5% by weight or more, nickel in an amount of 40% by weight or more, and chromium in an amount of 1% by weight or more.

14. The /4 type radio wave absorber according to claim 10, wherein the resistive film contains molybdenum in an amount of 5% by weight or more, nickel in an amount of 40% by weight or more, and chromium in an amount of 1% by weight or more.

15. The /4 type radio wave absorber according to claim 11, wherein the resistive film contains molybdenum in an amount of 5% by weight or more, nickel in an amount of 40% by weight or more, and chromium in an amount of 1% by weight or more.

Description

DESCRIPTION OF EMBODIMENTS

[0035] Embodiments of the present invention are more specifically described in the following with reference to, but not limited to, examples.

EXAMPLE 1

[0036] A polyethylene terephthalate (PET) film having a thickness of 75 m was provided as a substrate. On the PET film was formed a resistive film having a thickness of 9.9 nm by DC pulsed sputtering. The sputtering was carried out using an alloy having a composition as shown in Table 1 as a target at an output of 0.4 kW with introduction of Ar gas at a flow rate of 100 sccm and at a pressure adjusted to 0.12 Pa. Next, on the formed resistive film was laminated a polycarbonate dielectric layer having a thickness of 300 m via an adhesive tape (707#4 available from Teraoka Seisakusho Co., Ltd., thickness of 30 m). Further, on the dielectric layer was laminated an aluminum reflective layer having a thickness of 2 mm via an adhesive tape. Thus, a /4 type radio wave absorber was obtained.

[0037] The thickness of the resistive film was measured in the same manner as in the case of the barrier layer.

EXAMPLE 2

[0038] A polyethylene terephthalate (PET) film having a thickness of 75 m was provided as a substrate. On the PET film was formed a barrier layer 1 having a thickness of 3.4 nm by DC pulsed sputtering using silicon as a target at an output of 1.0 kW with introduction of Ar gas at a flow rate of 100 sccm and oxygen gas at a flow rate of 10 sccm and at a pressure adjusted to 0.12 Pa. Next, on the barrier layer 1 was formed a resistive film having a thickness of 9.1 nm by DC pulsed sputtering. The sputtering was carried out using an alloy having a composition as shown in Table 1 as a target at an output of 0.4 kW with introduction of Ar gas at a flow rate of 100 sccm and at a pressure adjusted to 0.12 Pa. Then, on the resistive film were laminated a dielectric layer and a reflective layer in the same manner as in Example 1. Thus, a /4 type radio wave absorber was obtained.

EXAMPLE 3

[0039] A polyethylene terephthalate (PET) film having a thickness of 75 m was provided as a substrate. On the PET film was formed a resistive film having a thickness of 9.1 nm by DC pulsed sputtering. The sputtering was carried out using an alloy having a composition as shown in Table 1 as a target at an output of 0.4 kW with introduction of Ar gas at a flow rate of 100 sccm and at a pressure adjusted to 0.12 Pa. Next, on the resistive film was formed a silicon dioxide barrier layer 2 having a thickness of 2.2 nm by DC pulsed sputtering under the conditions of using silicon as a target at an output of 1.0 kW with introduction of Ar gas at a flow rate of 100 sccm and oxygen gas at a flow rate of 10 sccm and at a pressure of 0.12 Pa. Then, on the barrier layer 2 were laminated a dielectric layer and a reflective layer in the same manner as in Example 1. Thus, a /4 type radio wave absorber was obtained.

EXAMPLE 4

[0040] A polyethylene terephthalate (PET) film having a thickness of 75 m was provided as a substrate. On the PET film was formed a barrier layer 1 having a thickness of 3.4 nm by DC pulsed sputtering under the conditions of using silicon as a target at an output of 1.0 kW with introduction of Ar gas at a flow rate of 100 sccm and oxygen gas at a flow rate of 10 sccm at a pressure of 0.12 Pa. Next, on the barrier layer 1 was formed a resistive film having a thickness of 9.2 nm by DC pulsed sputtering. The sputtering was carried out using an alloy having a composition as shown in Table 1 as a target at an output of 0.4 kW with introduction of Ar gas at a flow rate of 100 sccm and at a pressure adjusted to 0.12 Pa. Next, on the resistive film was formed a silicon dioxide barrier layer 2 having a thickness of 2.2 nm by DC pulsed sputtering under the conditions of using silicon as a target at an output of 1.0 kW with introduction of Ar gas at a flow rate of 100 sccm and oxygen gas at a flow rate of 10 sccm at a pressure of 0.12 Pa. Then, on the barrier layer 2 were laminated a dielectric layer and a reflective layer in the same manner as in Example 1. Thus, a /4 type radio wave absorber was obtained.

EXAMPLES 5 AND 6

[0041] A /4 type radio wave absorber was obtained in the same manner as in Example 4, except that the thicknesses of the resistive film and the barrier layers 1 and 2 were changed as shown in Table 1.

EXAMPLE 7

[0042] A /4 type radio wave absorber was obtained in the same manner as in Example 2, except that the thickness of the barrier layer 1 was changed as shown in Table 1.

EXAMPLE 8

[0043] A /4 type radio wave absorber was obtained in the same manner as in Example 3, except that the thickness of the barrier layer 2 was changed as shown in Table 1.

EXAMPLES 9 TO 12

[0044] A /4 type radio wave absorber was obtained in the same manner as in Example 4, except that the composition of the alloy used as a sputtering target and the thickness of the resistive film were changed as shown in Table 1.

COMPARATIVE EXAMPLE

[0045] A /4 type radio wave absorber was obtained in the same manner as in Example 1, except that the composition and the thickness of the resistive film were changed as shown in Table 1.

COMPARATIVE EXAMPLE 2

[0046] A /4 type radio wave absorber was obtained in the same manner as in Example 4, except that the composition and thickness of the resistive film and the thicknesses of the barrier layers 1 and 2 were changed as shown in Table 1.

<Evaluation>

[0047] The /4 type radio wave absorbers obtained in the examples and comparative examples were evaluated by the following methods.

[0048] Table 1 shows the results.

(Evaluation on Electromagnetic Wave Absorption Performance)

[0049] A PNA microwave network analyzer N5227A (available from Keysight Technologies), a PNA-X series 2-port millimeter-wave controller N5261A (available from Keysight Technologies), and a horn antenna FSS-07 (available from HVS Technologies, Inc.) were used to set up a radio wave absorption measuring device. Using this radio wave absorption measuring device, the radio wave absorption at W band (75 to 110 GHz) by the obtained /4 type radio wave/electromagnetic wave absorbers was measured in conformity with JIS R1679. The /4 type radio wave absorbers were set in such a manner that the radio wave was incident in a normal direction from the substrate side. The electromagnetic wave absorption performance was evaluated based on the obtained absorption amounts. Cases where the maximum radio wave absorption within the measurement range was 20 dB or more were rated A. Cases where the maximum radio wave absorption within the measurement range was less than 20 dB were rated B.

(Evaluation on Retention of Electromagnetic Wave Absorption Performance)

[0050] On each end of the resistive film in each of the examples and comparative examples was formed an electrode using silver paste. Between the electrodes were laminated a dielectric layer and a reflective layer in the same manner as in Example 1. Thus, a test /4 type radio wave absorber corresponding to each of the examples and comparative examples was prepared. The resistance value was measured after the preparation (resistance before a high-temperature high-humidity test). Next, the test /4 type radio wave absorber was subjected to a high-temperature high-humidity test in which the test /4 type radio wave absorber is left to stand at a temperature of 85 C. and a humidity of 85% for 500 hours. Then, the resistance was measured. The change rate (resistance after the test/resistance before the test) of the resistance before and after the test was calculated from the obtained resistance values, and the retention of the electromagnetic wave absorption performance was evaluated.

TABLE-US-00001 TABLE 1 Example 1 2 3 4 5 6 7 Resistive Composition Mo 16.4 16.4 16.4 16.4 16.4 16.4 16.4 film (wt %) Ni 51.2 51.2 51.2 51.2 51.2 51.2 51.2 Cr 17.5 17.5 17.5 17.5 17.5 17.5 17.5 Fe 11.1 11.1 11.1 11.1 11.1 11.1 11.1 W 3.2 3.2 3.2 3.2 3.2 3.2 3.2 Mn Co Si 0.6 0.6 0.6 0.6 0.6 0.6 0.6 Thickness (nm) 10.7 9.8 9.8 10.0 10.5 9.8 9.8 Barrier layer 1 Composition SiO.sub.2 SiO.sub.2 SiO.sub.2 SiO.sub.2 SiO.sub.2 Thickness (nm) 3.4 3.4 0.8 9.3 9.3 Barrier layer 2 Composition SiO.sub.2 SiO.sub.2 SiO.sub.2 SiO.sub.2 Thickness (nm) 2.2 2.2 0.8 9.3 Reflective layer Composition Al Thickness (mm) 2 Evaluation Electromagnetic wave A A A A A B B absorption performance Retention of electromagnetic 2.24 1.35 1.35 1.19 1.43 1.79 2.01 wave absorption performance (Change rate, %) Comparative Example Example 8 9 10 11 12 1 2 Resistive Composition Mo 16.4 5.5 28.0 13.0 film (wt %) Ni 51.2 43.0 68.5 56.0 47.0 87.2 87.2 Cr 17.5 30.0 1.0 22.0 22.0 8.9 8.9 Fe 11.1 15.0 1.0 3.0 18.0 3.9 3.9 W 3.2 2.5 3.0 0.5 Mn 1.5 0.5 0.5 1.0 Co 2.0 0.5 2.4 1.5 Si 0.6 0.5 0.5 0.1 1.0 Thickness (nm) 9.8 10.1 9.9 10.3 10.1 7.3 7.3 Barrier layer 1 Composition SiO.sub.2 SiO.sub.2 SiO.sub.2 SiO.sub.2 SiO.sub.2 Thickness (nm) 3.4 3.4 3.4 3.4 3.2 Barrier layer 2 Composition SiO.sub.2 SiO.sub.2 SiO.sub.2 SiO.sub.2 SiO.sub.2 SiO.sub.2 Thickness (nm) 9.3 2.2 2.2 2.2 2.2 3.2 Reflective layer Composition Al Thickness (mm) 2 Evaluation Electromagnetic wave B A A A A A A absorption performance Retention of electromagnetic 1.94 1.72 1.69 1.14 1.45 wave absorption performance (Change rate, %)

INDUSTRIAL APPLICABILITY

[0051] The present invention can provide a /4 type radio wave absorber having excellent durability.