KR20060044518A - Electric wave absorption sheet material and electric wave absorber using the same - Google Patents

Abstract

The present invention provides a radio wave absorbing sheet material excellent in isotropy with respect to dielectric loss characteristics and a radio wave absorber using the same.

A corrugated structure is formed by laminating a planar liner and a center in which a corrugated sheet containing an electrical loss material containing electrical loss material is processed, wherein the electrical loss material containing sheet has the largest dielectric constant in a plane shape plane. the dielectric loss (ε _"(v between the ratio _{(ε" p / ε "v} ) p) and the direction (v) the dielectric loss ε) in perpendicular to the direction" according to the direction (p) indicates a loss 1.2 An electromagnetic wave absorbing sheet member having anisotropy of 4 to 4 and formed by wave-processing the electrical loss material-containing sheet so that the direction showing the maximum dielectric loss is substantially orthogonal to the ridge line of the top of the waveform.

Electromagnetic wave absorber, electromagnetic wave absorber sheet material, electrical loss material containing sheet

Description

Electric wave absorbing sheet material and electric wave absorber using same {Electric Wave Absorption Sheet Material and Electric Wave Absorber Using the Same}

[Document 1] Japanese Unexamined Patent Application Publication No. 11-87978

[Document 2] Japanese Unexamined Patent Publication No. 2000-216584

[Document 3] Japanese Unexamined Patent Publication No. 2004-253760

The present invention relates to a radio wave absorbing sheet material and a radio wave absorber using the same.

Radio darkrooms are used for measurement tests of various characteristics of antennas and radio wave measurement tests of electronic devices. Radio wave absorbers are mounted on the walls, ceilings, floors, and the like of radio wave darkrooms to shield the intrusion of radio waves from the outside and to prevent radio waves generated from the device under measurement from being radiated to the outside.

Many of the radio wave absorbers used for this purpose were molded of resin foams such as foamed urethane and foamed styrene impregnated with carbon black, which is a conductive material. However, since the radio wave absorber molded from the resin foam is large in volume and weak, the leading edge of the molded body may be damaged by vibration during transportation or collision with other objects. As a result, the storage space is increased, so that the storage cost is increased, and a large volume is required for packing to protect from damage during transportation, which causes a high transportation cost and a cost increase.

As a countermeasure for such a problem, it is disclosed to carry in as a carbon black containing board | plate material to a construction site, and to assemble it into the electromagnetic wave absorber, such as a hollow pyramid shape, at the construction site (refer documents 1, 2 etc.). However, if the carbon black-containing sheet material is too thin, it causes distortion and shape instability in the radio wave absorber after assembly due to lack of rigidity. Therefore, it is necessary to increase the thickness of the plate material to about 5 to 20 mm. However, as a result of the thickening of the sheet, the weight of the sheet increases, resulting in deterioration in field workability, incurring a low transportation cost, and a large amount of carbon black.

In view of such a problem, the present inventors have invented a radio wave absorbing sheet member including a corrugated plate structure in which a center line processed into a wave shape and a planar liner are laminated (see Document 3 as a prior application). Since the said electromagnetic wave absorption sheet | seat material is based on a corrugated-board structure, it is lightweight, including a hollow part inside, and can convey | laugh and carry | assemble well in the field. Especially, in order to protect the electrical loss material used as an essential part of absorption characteristics, and to acquire the stable characteristic in a long term, it is more preferable to use the sheet | seat containing an electrical loss material in a center part of a wave shape.

However, if the radio wave absorbing sheet material has the anisotropy in its dielectric loss characteristics including the above technique, it takes time for the radio wave absorber to be designed, or a problem such as a decrease in yield in order to align the mold against the sheet occurs. Therefore, it was a subject to solve the said anisotropy.

An object of the present invention is to provide a radio wave absorbing sheet material excellent in isotropy with respect to dielectric loss characteristics and a radio wave absorber using the same.

That is, this invention includes the following structures.

[1] An electrical loss material-containing sheet includes a corrugated board structure in which a center line formed by corrugating a sheet containing an electrical loss material and a planar liner are laminated, and the electrical loss material-containing sheet is in planar shape. the dielectric loss (ε _"(v between the ratio _{(ε" p / ε "p} ) and dielectric loss ε) in the direction (v) perpendicular to the direction" _v in a direction (p) represents the maximum dielectric loss of ) Is an anisotropy having 1.2 to 4, and the electrical wave absorbing sheet member is wave-formed so that the electrical loss material-containing sheet is subjected to wave processing so that the direction showing the maximum dielectric loss is substantially orthogonal to the ridge of the top of the waveform.

[2] The radio wave absorbing sheet member according to claim 1, wherein the electrical loss material-containing sheet is kneaded paper containing conductive fibers.

[3] The radio wave absorption sheet member according to claim 2, wherein a fiber length of the conductive fiber is in a range of 2 mm to 20 mm.

[4] The radio wave absorption sheet member according to claim 2 or 3, wherein a content of the conductive fiber is 0.1 to 10% by mass.

[5] The radio wave absorbing sheet member according to any one of claims 2 to 4, wherein the electrical loss material-containing sheet further comprises a flame retardant fiber.

[6] The radio wave absorbing sheet member according to any one of claims 2 to 5, wherein the electrical loss material-containing sheet further comprises 11 to 63.9 mass% of cellulose fibers and 36 to 88.9 mass% of a hydrous inorganic compound.

[7] The radio wave absorbing sheet member according to any one of Claims 2 to 6, wherein the kneaded paper is wetted by a wet papermaking method using water as a medium.

[8] The radio wave absorbing sheet member according to any one of claims 1 to 7, wherein a basis weight of the electrical loss member-containing sheet is 120 to 200 g / m ² .

[9] The gap between the tops of any one of claims 1 to 8, wherein the peak height of the center in which the electrical loss material-containing sheet is processed into waves is 2 to 5 mm. The electromagnetic wave absorption sheet material which is 4-15 mm.

[10] The radio wave absorption sheet member according to claim 9, wherein an acid height of the center is 2.5 to 5 mm.

[11] The radio wave absorbing sheet member according to any one of claims 1 to 10, wherein the planar liner comprises 12 to 60 mass% of cellulose fibers and 40 to 88 mass% of a hydrous inorganic compound.

[12] The radio wave absorption sheet material according to any one of claims 1 to 11, wherein a basis weight of the planar liner is 120 to 400 g / m ² .

[13] The radio wave absorbing sheet member according to any one of claims 1 to 12, wherein the corrugated sheet has a structure in which a plurality of center sheets are laminated.

[14] The center of claim 13, wherein the plurality of stacked centers includes a center including the electrical loss material-containing sheet and a center containing no electrical loss material. Electromagnetic wave absorption sheet material comprising a.

[15] The radio wave absorption sheet material according to any one of claims 1 to 14, wherein the planar compressive strength is 40 to 250 kPa.

[16] The radio wave absorption sheet member according to any one of claims 1 to 15, wherein the vertical compressive strength is 1.5 to 8 kN / m.

[17] A radio wave absorber comprising the radio wave absorption sheet member according to any one of items 1 to 16.

[18] The electromagnetic wave absorber according to claim 17, wherein a plurality of electromagnetic wave absorbing sheet materials are laminated.

[19] The radio wave absorber according to claim 17, wherein the radio wave absorbing sheet member is assembled from a hollow three-dimensional structure having a shape selected from a wedge shape, a polygon weight, and a polygonal column shape.

[20] The radio wave absorber according to claim 19, wherein the hollow solid structure is provided on a sintered ferrite plate.

[21] The radio wave absorber according to claim 19, wherein the hollow solid structure is provided on a plate-like body formed by laminating a plurality of the radio wave absorption sheet members.

Best Mode for Carrying Out the Invention

The electromagnetic wave absorbing sheet member of the present invention includes a corrugated board structure in which a center lined with a planar liner and a center of a sheet containing an electrical loss member are processed in a wave form.

The electrical loss material converts radio wave energy into a small current and also attenuates radio waves by converting it into thermal energy. As such an electrical loss material, conductive powders, such as carbon black, carbon micro coil powder, and graphite powder, and conductive fibers, such as carbon fiber, silicon carbide fiber, a metal fiber, and metal plating fiber, are mentioned, for example. Moreover, the semiconductor fiber obtained by making baking temperature into the low temperature of 50-700 degreeC with respect to normal baking temperature 1000 degreeC or more of carbon fiber and silicon carbide fiber may be sufficient.

As the form of an electrical loss material in an electrical loss material containing sheet, it is especially preferable to set it as the conductive fiber in blend paper. It is because the anisotropy of the dielectric loss characteristic of an electrical loss material containing sheet | seat becomes easy to control by orienting conductive fiber in kneaded paper. In other words, if the degree of orientation of the conductive fibers is low, the anisotropy of the dielectric loss characteristics of the electrical loss material-containing sheet is low. If the degree of orientation of the conductive fibers is high, the anisotropy of the dielectric loss characteristics of the electrical loss material-containing sheet is increased. Among these conductive fibers, carbon fibers are preferred because of their low specific gravity and easy mixing, and because the fibers themselves are rigid, the fibers are easily oriented.

In addition, the fiber length of the conductive fiber is preferably 2 to 20 mm. By setting it as 2 mm or more, it becomes easy to control the orientation of a fiber by making it random, and also by setting it as 20 mm or less, the fiber is prevented from becoming entangled and also control of orientation becomes easy.

As for the compounding quantity of a conductive fiber, 0.1-10 mass% is preferable. By setting it as 0.1 mass% or more, sufficient radio wave absorption effect can be expressed, and by setting it as 10 mass% or less, since there is no excessive conductive fiber powder, orientation becomes easy to control.

In addition, the honcho paper also preferably contains flame retardant fibers. It is because it is preferable to provide flame retardancy as a radio wave absorption sheet from a viewpoint of safety since radio wave absorption is conversion of radio wave energy into heat energy as mentioned above.

Examples of such flame retardant fibers include glass fibers, aromatic polyamide fibers, polyether ether ketone fibers, polyparaphenylene benzobisoxazole fibers, polyphenylene sulfide fibers, and the like. Moreover, what impregnated the resin mixture containing a flame retardant with the fiber containing nonflammable resin, and impregnated it, and also made it into a flame retardant fiber can be used preferably. As such a flame retardant, it is preferable not to contain a halogen element with a large environmental load, and if it is one or more types selected from condensation phosphate ester, phosphate ester, aromatic diphosphate, magnesium hydroxide, aluminum hydroxide, and red phosphorus, the amount of addition of at least high flame retardancy may be improved. It is preferable because an effect is obtained.

It is also preferable that the mixed paper of the electrical loss material-containing sheet contains 11 to 63.9 mass% of cellulose fibers and 36 to 88.9 mass% of a hydrous inorganic compound in addition to the conductive fibers. Since cellulose fiber is hydrophilic and has a property of heat shrinking, appropriate rigidity can be imparted to the sheet by the action of heat in the bonding of the bone and moisture contained in the grass. However, since cellulose fiber has the weakness which is easy to burn, it is preferable to provide flame retardance by using together with a hydrous inorganic compound. As such a hydrous inorganic compound, aluminum hydroxide etc. can be used preferably. By making cellulose fiber 11 mass% or more, appropriate rigidity can be provided. In addition, the upper limit of content of a cellulose fiber is determined by the lower limit of content of the conductive fiber and hydrous inorganic compound used together. Moreover, flame retardance can be provided by making a hydrous inorganic compound into 36 mass% or more. In addition, the upper limit of content of a hydrous inorganic compound is determined by the lower limit of content of the cellulose fiber used together.

As a manufacturing method of a honcho paper, the wet papermaking method which raises and raises the slurry which mixed the fiber and water, and the dry papermaking method which stir-mixes fiber in air, and collects this in a sheet form are mentioned. In either of the wet papermaking method and the dry papermaking method, the orientation of the fibers in the blended paper can be controlled by the traveling speed of the net conveyor continuously moving to the lifting and raising means. In other words, if the running speed of the net conveyor is increased, the orientation of the conductive fibers proceeds. If the running speed is slowed, the orientation of the conductive fibers tends to be suppressed. It is considered that the cause of such a tendency is that the resistance of a medium such as water with respect to the conductive fiber changes depending on the traveling speed of the net conveyor.

In addition, the wet papermaking method and the dry papermaking method are more preferable in that the wet papermaking method can be uniformly floated while maintaining its properties without damaging the conductive fiber.

Moreover, in these papermaking methods, it is also preferable to add an inorganic binder and organic binders, such as starch, polyvinyl alcohol, polyethylene, paraffin, and acrylic fiber. By adding the binder, the paper can be peeled off from the paper network.

Moreover, as a basis weight of the electrical loss material containing sheet used for a center, 120-200 g / m <^2> is preferable. By setting it as 120 g / m <^2> or more, it can prevent that a sheet tear etc. generate | occur | produce when processing into a wave shape and adhere | attaching to a planar liner. Moreover, waveform processing becomes easy by setting it as ²⁰ g / m <^2> or less.

The electrical loss material-containing sheet used as the electromagnetic wave absorbing sheet member of the present invention has a dielectric loss ε &_quot; _p in the direction p showing the largest dielectric loss in the plane-shaped plane and a direction perpendicular to this direction (v). It is important that the ratio (ε &_quot; _p / ε " _v ) to the dielectric loss (ε " _v ) in N) is 1.2 to 4 for propagation in the frequency range of 3 to 18 GHz. Radio waves in the frequency range of 3 to 18 GHz have a suitable length of several tens of cm to several mm, are relatively easy to handle, and a sample size necessary for measurement is also easy to handle at about 30 cm x 30 cm. As a result, it is possible to precisely measure ε &quot;. In addition, ε &_quot; _p / ε " _v measured in other frequency ranges has a certain degree of correlation (however, resonance occurs specifically at a specific frequency). Even if it is desired to obtain an electromagnetic wave absorbing sheet having an absorption in the frequency range other than that, the purpose is to adjust the ε " _p / ε" _v measured at 3 to 18 GHz to the above range. Here, the dielectric loss is one of the indexes indicating the magnitude of the damping action by the energy conversion as described above, and is defined as the imaginary part ε "of the relative dielectric constant ε in the following equation.

ε = ε'-jε "

The anisotropy is essential for the electrical loss material-containing sheet used in the present invention in order to offset the anisotropy of the dielectric loss due to the shape, i.e., processing by the waveform as the center of the corrugated plate.

Further, when ε &_quot; _p / ε " _v is smaller than 1.2, it is difficult to fully absorb the anisotropy of the dielectric loss due to the shape, and when it is larger than 4, it is not completely absorbed by the anisotropy of the dielectric loss due to the shape. ε " _p / ε" _v can be adjusted by controlling the orientation state of the conductive fiber in papermaking as mentioned above.

A means for canceling the anisotropy of dielectric loss due to the intrinsic dielectric loss and shape of the dielectric loss-containing sheet, the direction (p) showing the maximum dielectric loss in the planar plane of the electrical loss-containing sheet. It is important to wave form so that the ridge of the top of the wave shape is approximately orthogonal.

That is, the present inventors found that in the anisotropy of the dielectric loss resulting from the wave shape, the dielectric loss becomes smaller in the wavelength direction of the center wave, and larger in the ridge direction of the top of the waveform directly parallel thereto. The combination of the large and small directions of the dielectric loss of each of the anisotropy due to intrinsic anisotropy and shape was derived to counterbalance the anisotropy.

From the viewpoint of canceling the intrinsic anisotropy due to the intrinsic anisotropy and the shape, the direction p showing the maximum dielectric loss in the planar plane of the sheet containing the electrical loss material and the ridgeline at the top of the waveform need not be orthogonal to each other. It can be crossed (approximately orthogonal) in the direction of the degree to which none of the above cancellation effects are obtained.

The shape of the wave shape at the center of the electrical loss material-containing sheet is formed between the top portions of which the height of the wave absorbing sheet material of the present invention forms a sieve as a corrugated plate (ie, twice the amplitude) of 1 mm or more and adjacent tops. It is preferable that the space | interval is 1 mm or more. Moreover, it is more preferable that acid height is 2-5 mm from a viewpoint of the above-mentioned offset effect, More preferably, it is 2.5-5 mm. Further, it is more preferable that the spacing between adjacent tops is 4 to 15 mm. The anisotropy resulting from a shape can be prevented from becoming large too much by making a height of 2 mm or more and a space | interval between adjacent top parts 4 mm or more. Moreover, the effect of canceling the intrinsic anisotropy of the electrical loss material containing sheet | seat as mentioned above becomes easy to be obtained by setting an acid height of 5 mm or less and the space | interval between adjacent top parts to 15 mm or less. From the standpoint of the corrugated plate member, the acid height is preferably within the above ranges in consideration of both the bonding strength and the joining workability, and the interval between adjacent tops is also determined by the number of steps and the strength required for the bonding step. In consideration of both, it is preferable to carry out in said range.

The electromagnetic wave absorbing sheet member of the present invention includes a corrugated board structure in which a corrugated center and a planar liner are laminated. For the reason described above, in the radio wave absorption sheet material of the present invention, it is important to use an electrical loss material-containing sheet for at least a part of the center processed into a wave shape, but use the electrical loss material-containing sheet as a center, By protecting with a liner, it is possible to avoid the dropping and deterioration of the electrical loss material due to the impact from the outside, and to maintain a stable radio wave absorbency for a long time. Moreover, by having a corrugated board structure, a hollow part can be contained and lightweight, and it is easy to carry. Moreover, since it has appropriate rigidity by embedding a center, the range of application to various electromagnetic wave absorbers is also wide.

The structure of the corrugated sheet is preferably selected from single sided corrugated board, double sided corrugated board, double sided corrugated board or triple wall to obtain as thin, light and strong sheet material as possible. Here, the single-sided corrugated board refers to a corrugated board structure in which a corrugated center is bonded to one liner, and the double-sided corrugated board refers to a corrugated board structure in which a corrugated center is joined between two liners. Plate refers to the structure of the bone plate bonded to one side of the double-sided corrugated plate, and triple wall refers to the structure of the three-layer structure by bonding the one-sided bone plate to the double-sided bone plate. Among them, the double-sided corrugated board is particularly preferred because it has both thinness and moderate rigidity.

In addition, in the case of satisfying the desired radio wave absorption characteristics as a center including one sheet containing the electrical loss material per sheet of the electromagnetic wave absorbing sheet, the center including the sheet containing the electrical loss material and the electrical loss member are not contained. Laminating | stacking and centering the center containing a sheet is preferable at the point which can improve strength, without raising manufacturing cost.

As a raw material of a planar liner, it is preferable that it is papermaking, and it is preferable that 12-60 mass% of cellulose fibers and 40-88 mass% of hydrous inorganic compounds are included. Since cellulose fibers are hydrophilic and have heat-shrinkable properties, proper stiffness can be imparted to the sheet by the action of heat contained in the glue and moisture contained in the glue. However, since cellulose fiber has the weakness which is easy to burn, it is preferable to provide flame retardance by using together with a hydrous inorganic compound. By making cellulose fiber 12 mass% or more, rigidity as a sheet can be provided. In addition, the upper limit of content of a cellulose fiber is determined by the lower limit of content of the hydrous inorganic compound used together. Moreover, flame retardance can be provided by making a hydrous inorganic compound into 40 mass% or more. In addition, the upper limit of content of a hydrous inorganic compound is determined by the lower limit of content of the cellulose fiber used together.

Moreover, as a basis weight of a planar liner, 120-400 g / m <^2> is preferable. By setting it as 120 g / m <^2> or more, it can prevent that a sheet tearing etc. generate | occur | produce at the time of adhesion | attachment with a center. On the other hand, if the basis weight is too large, the cost will increase, so it may be about 400 g / m ² .

In the radio wave absorbing sheet material of the present invention, as an example of a method for obtaining a corrugated board structure, a known paper corrugated board manufacturing method can be used at a high speed and at a low manufacturing cost. Specifically, a corrugated machine creates a corrugation in the center and pastes it on the outer or inner liner to make a single-sided corrugated sheet. In addition, the same collator may be heated while bringing the one-side corrugated board and the liner into close contact with each other, and may be used as a double-sided or double-sided corrugated board and sent to a cutter to cut to a predetermined dimension.

Well-known adhesive agents, such as starch paste, can be used as an adhesive agent which adhere | attaches the members which comprise a corrugated board, such as a center and a planar liner.

It is preferable that the electromagnetic wave absorption sheet material of this invention is 40-250 kPa of planar compressive strength. When the plane compressive strength is 40 kPa or more, the surface is hardly scratched even when subjected to impact during transportation or assembly, and the handling properties are excellent. From this point of view, it is preferable that the planar compressive strength is larger, but the weight tends to increase even if it is too large, so that it may be about 250 kPa so as not to impair handling property.

Moreover, it is preferable that the electromagnetic wave absorption sheet | seat material of this invention is 1.5-8 kN / m of vertical compressive strength. By setting the vertical compressive strength to 1.5 kN / m or more, good dimensional stability is obtained even when a large structure is obtained. From this point of view, the higher the vertical compressive strength is, the more the weight tends to increase even if it is too large, so that the handling property may be about 8 kN / m so as not to impair handling.

Next, the electromagnetic wave absorber of the present invention includes the electromagnetic wave absorbing sheet member of the present invention.

As a form of the electromagnetic wave absorber of this invention, what is obtained by laminating | stacking a several sheets the electromagnetic wave absorption sheet material of this invention, for example is preferable. This is because the frequency of radio waves that can be absorbed can be adjusted by adjusting the number of laminated sheets and the amount of electrical loss material included in the center. Moreover, in such a laminated structure, it is also preferable to mix the corrugated board which does not contain an electrical loss material containing sheet in adjusting the frequency of the radio wave which can be absorbed.

Moreover, as another aspect, it is also preferable to be assembled to the hollow three-dimensional structure which is wedge shape, polygonal cone shape, or polygonal columnar shape. Such a hollow structure is preferable from the viewpoint of saving transportation and storage costs because the hollow structure can be transported in a state of being folded or in a folded state and can be assembled near an installation site. In addition, since the corrugated plate has an appropriate rigidity, the shape retention of the radio wave absorber after assembly can be improved.

Moreover, it is also preferable to provide the said hollow three-dimensional structure by standing on a sintered ferrite board. By combining with the sintered ferrite plate, low frequency radio waves of about 30 MHz to 300 GHz can be absorbed.

Moreover, it is also preferable to provide the said hollow three-dimensional structure on the flat electromagnetic wave absorber of this invention formed by laminating | stacking the several electromagnetic wave absorption sheet material of this invention. By combining with the radio wave absorber of the present invention on a flat plate, it is possible to absorb radio waves of about 1 to 100 GHz.

In this way, the electromagnetic wave absorbing sheet member of the present invention can be made into a radio wave absorber according to a desired frequency, depending on the form of the electromagnetic wave absorber and the material used in combination.

The electromagnetic wave absorbing sheet member of the present invention can be used as a structural member of a radio wave absorber constituting the wall surface of a radio wave dark room. Moreover, it can be used also as interior materials, such as moving objects, such as a ship and an aircraft, bridges, structures, such as a steel tower, the apparatus and facilities for wireless communication, buildings, such as buildings, and office supplies. Moreover, it can also be used as an electromagnetic wave shield wallpaper used for a simple shield room, and the unnecessary wave suppression sheet mounted around an electronic circuit. In this way, it can be used as an electronic environmental countermeasure material of various forms for absorbing unnecessary reflection waves and preventing radio interference.

<Example>

The present invention is explained in more detail by the following examples. In addition, the performance value shown in the Example was measured with the following method.

[How to measure]

(1) dielectric loss

Samples were placed on the front of an aluminum plate 30 cm long x 30 cm wide by 1 mm thick, using a double ridge guide horn antenna mounted on an arch measuring instrument, and a network analyzer manufactured by Azirent Technologies. Input impedance at 3 to 18 GHz was measured. Thereafter, the sample was removed and the input impedance at 3 to 18 GHz was measured with the spacer alone, and the relative dielectric constant of the sample was obtained by inversion from the difference between the impedances with and without the samples.

The direction p indicating the maximum dielectric loss of the sample was determined by defining a linear axis on the sample plane, and rotating the determined linear axis to 90 ° at 10 ° intervals to determine the 10-direction linear axis. Ten samples were selected so that one side of a 30 cm × 30 cm sample was parallel to each of the linear axes. Then, the propagation is made so that the direction of electric field oscillation of the radio wave irradiated from the double ridge guide horn antenna is parallel to each direction axis, and the input impedance is measured and the linear axis direction of the largest sample of the relative dielectric constant is measured. p).

(2) radio wave absorbency

The reflection level when the radio wave was vertically applied to an aluminum plate having a height of 60 cm x 60 cm x 1 mm in thickness was measured using the network analyzer, and then the same was applied to the radio wave absorber having the same area. It calculated | required from the difference of the reflection level shown by a formula.

Radio wave absorption (dB) = reflection level of radio wave absorber (dB)-reflection level of aluminum plate (dB)

(3) flame retardant

It measured according to UL 94 "Combustibility test of plastic material for component parts of equipment".

(4) flat compressive strength

It measured according to JIS Z 0403-1 "Corrugate-Part 1: Plane compressive strength test method".

(5) vertical compressive strength

It measured according to JIS Z 0403-2 "Corrugate-Part 2: Vertical compressive strength test method."

<Example 1>

(Center sheet)

The following fibers and hydrous inorganic compounds were mixed as media as water at the ratio of the corresponding substrates respectively, wet paper-making at a winding speed of 100 m / min, and an electrical loss material having a thickness of 0.1 mm and a basis weight of 100 g / m ² . Sheet A containing was obtained.

PAN carbon fiber having an average fiber length of 6 mm and a fiber diameter of 7 µm: 0.8 mass%

Chopped glass fibers with a fiber length of 6 mm and a fiber diameter of 7 μm: 29.2 mass%

Aramid pulp with an average fiber length of 1 mm: 10 mass%

Aluminum hydroxide: 60 mass%

The direction showing the maximum dielectric loss in the plane of this sheet A was the papermaking flow direction, and the direction showing the minimum dielectric loss was the paper width direction. Table 1 shows the dielectric losses (ε " _p , ε" _v ) and their ratios (ε " _p / ε" _v ) in these two directions.

Frequency (GHz) Center Sheet A Dielectric loss ratio ε " _p ε " _v ε " _p / ε" _v 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 346 300 271 277 249 214 169 149 132 120 119 118 117 103 100 90 189 164 148 145 130 114 94 83 80 79 78 70 64 58 56 50 1.8 1.8 1.8 1.9 1.9 1.9 1.8 1.8 1.7 1.5 1.5 1.7 1.8 1.8 1.8 1.8

As shown in Table 1, ε &_quot; _p / ε " _v was 1.5 to 1.9 for radio waves of 3 to 18 GHz.

(Sheet for flat liner)

The following fibers and hydrous inorganic compounds were mixed as media as water at the ratio of the corresponding substrates respectively, wound up and wet paper-wound at a speed of 100 m / min, with an electrical loss of 0.12 mm in thickness and 100 g / m ² basis weight. A sheet B containing no ash was obtained.

Red glass fiber with a fiber length of 6 mm and a fiber diameter of 7 μm: 30 mass%

Aramid pulp with an average fiber length of 1 mm: 10 mass%

Aluminum hydroxide: 60 mass%.

(Electric wave absorption sheet material)

The center sheet A is processed into a corrugator so that the direction showing the maximum dielectric loss in the plane of the sheet and the ridge of the top of the waveform are orthogonal, and the peak height of 2.5 mm and the distance between the adjacent tops A center of 5 mm was made.

Subsequently, the center and the planar liner sheet B were bonded together with a starch-based adhesive having a coating amount of 5 g / m ² , using the same collator, to produce a radio wave absorbing sheet member C having a double-sided corrugated board structure. At this time, the sending direction (length direction) of the manufacture of the corrugated board was made to be orthogonal to the ridgeline direction of the top of the center.

Table 2 shows the dielectric loss of the electromagnetic wave absorption sheet member C between the case where an electric field was applied in parallel to the longitudinal direction of the corrugated plate and the case where an electric field was applied in parallel to the width direction.

Frequency (GHz) Radio wave absorption sheet material C ratio Longitudinal direction Width direction 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 5.3 4.9 4.3 3.6 2.9 2.9 2.4 1.9 1.8 1.5 1.4 1.6 1.6 1.5 1.1 1 3.6 3.6 3.4 3.5 2.7 2.8 2.2 1.8 1.7 1.5 1.3 1.6 1.6 1.4 1.1 1 1.5 1.4 1.3 1.0 1.1 1.0 1.1 1.1 1.1 1.0 1.1 1.0 1.0 1.1 1.0 1.0

The electromagnetic wave absorbing sheet member C obtained as shown in Table 2 had very low anisotropy of dielectric loss. Moreover, the said electromagnetic wave absorption sheet | seat material C had flame retardance equivalent to UL94 V-0, planar compressive strength was 65 kPa, and the vertical compressive strength was 2 kN / m.

<Example 2>

(Wave absorber)

Two electromagnetic wave absorbing sheet members C obtained in Example 1 were laminated in the direction of the center, and the layers were bonded together with a starch-based adhesive, cut into dimensions of 60 cm x 60 cm, thereby producing a radio wave absorber.

Table 3 shows the radio wave absorption properties of the electromagnetic wave absorber when the electric field is applied in parallel to the longitudinal direction of the corrugated plate and when the electric field is applied in the width direction.

Frequency (GHz) Radio wave absorber Radio wave absorption amount (dB) ratio Longitudinal direction Width direction 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 10 15 17 30 7 8 5 4 3 2 2 2 2 2 2 1 9 14 18 25 7 8 4 4 3 2 2 2 2 1 1 1 1.1 1.1 0.9 1.2 1.0 1.0 1.3 1.0 1.0 1.0 1.0 1.0 1.0 2.0 2.0 1.0

As shown in Table 3, the obtained radio wave absorber was very small in the anisotropy of radio wave absorbency.

<Example 3>

(Center sheet)

The following fibers and hydrous inorganic compounds were respectively mixed in the ratio of the corresponding base material with water as a medium, wet papermaking at a winding speed of 60 m / min, and containing an electrical loss material of 0.15 mm thickness and basis weight 120 g / m ² . Sheet D was obtained.

PAN carbon fiber having an average fiber length of 12 mm and a fiber diameter of 7 µm: 0.4 mass%

Cellulose fibers with an average fiber length of 2 mm: 20 mass%

Acrylic short fiber of 6 mm of fiber length and 20 micrometers of fiber diameters: 4.6 mass%

Aluminum hydroxide: 75 mass%.

The direction showing the maximum dielectric loss in the plane of this sheet D was the paper flow direction, and the direction showing the minimum dielectric loss was the paper width direction. The dielectric losses of these two directions (ε " _p , ε" _v ) and their ratios (ε " _p / ε" _v ) are shown in Table 4.

Frequency (GHz) Central Sheet Dielectric loss ratio ε " _p ε " _v ε " _p / ε" _v 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 171 154 132 115 106 91 80 80 76 69 62 55 48 45 38 35 110 95 82 72 65 56 50 52 50 46 50 40 35 32 25 25 1.6 1.6 1.6 1.6 1.6 1.6 1.6 1.5 1.5 1.5 1.2 1.4 1.4 1.4 1.5 1.4

As shown in Table 4, ε " _p / ε" _v was 1.2 to 1.6 for radio waves of 3 to 18 GHz.

(Sheet for flat liner)

The following fiber and water-containing inorganic compounds were mixed as media as water, respectively, as a medium, wet papermaking at a winding speed of 100 m / min, and an electric loss material having a thickness of 0.18 mm and a basis weight of 160 g / m ² . Sheet E which does not contain was obtained.

Cellulose fibers with an average fiber length of 2 mm: 20 mass%

Acrylic short fiber of 6 mm of fiber length and 20 micrometers of fiber diameters: 5 mass%

Aluminum hydroxide: 75 mass%.

(Electric wave absorption sheet material)

With respect to the center sheet D, the sheet is processed into a corrugator so that the direction showing the greatest dielectric loss in the sheet surface and the ridge of the top of the waveform are orthogonal, and the peak height 3.5 mm and the distance between neighboring tops A center of 8.8 mm was made.

Subsequently, the center and the planar liner sheet E were bonded together with a starch-based adhesive agent having a coating amount of 5 g / m ² , using the same collider, thereby producing a radio wave absorbing sheet member F having a double-sided corrugated board structure. At this time, the sending direction (length direction) of the manufacture of the corrugated board was made to be orthogonal to the ridgeline direction of the top of the center.

Table 5 shows the dielectric loss of the electromagnetic wave absorbing sheet member F between the case where an electric field was applied parallel to the longitudinal direction of the corrugated plate and the case where an electric field was applied parallel to the width direction.

Frequency (GHz) Electric wave absorption sheet material F ratio Longitudinal direction Width direction 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 4.2 4 3.8 3.5 3.1 2.8 2.3 1.2 1.8 1.2 1.1 1.2 1.3 1.2 1.1 1 4.5 4 4 3.5 3 2.6 2.4 1.1 1.7 1.3 1.3 1.2 1.4 1.3 1.1 1 0.9 1.0 1.0 1.0 1.0 1.1 1.0 1.1 1.1 0.9 0.8 1.0 0.9 0.9 1.0 1.0

The radio wave absorption sheet member F obtained as shown in Table 5 had very low anisotropy of dielectric loss. Moreover, the said electromagnetic wave absorption sheet | seat material F had flame retardance equivalent to UL 94 VTM-1, planar compressive strength was 85 kPa, and the vertical compressive strength was 25 kN / m.

<Example 4>

(Wave absorber)

From the radio wave absorption sheet | seat material F obtained in Example 3, 4 sheets of equilateral triangles of the base 60cm and the height 150cm were cut out. At this time, the cutting was performed so that the height direction of the equilateral triangle and the longitudinal direction of the corrugated plate were parallel.

The equilateral sides of these two isosceles triangular 4 sheets were bonded together with an adhesive tape to produce a hollow pyramidal structure having a hollow pyramid shape of 60 cm × 60 cm.

This radio wave absorber was also mounted on a sintered ferrite tile having a dimension of 60 cm x 60 cm.

As a result of measuring the radio wave absorption characteristics of the radio wave absorber of 30 MHz to 18 GHz, good absorption characteristics of 20 dB or more were obtained over the entire frequency range. In addition, since the radio wave absorber has appropriate rigidity, the dimensions of the structure were maintained well even when the place was moved.

Example 5

(Wave absorber)

In the radio wave absorption sheet | seat material F obtained in Example 3, four isosceles triangles of 60 cm in base and 150 cm in height were cut out. At that time, cutting was carried out so that the height direction of the equilateral triangle and the longitudinal direction of the corrugated plate became vertical.

The equilateral sides of these two isosceles triangular 4 sheets were bonded together with an adhesive tape to produce a hollow pyramidal structure having a hollow pyramid shape of 60 cm × 60 cm.

Further, this radio wave absorber was mounted on a sintered ferrite tile having a dimension of 60 cm x 60 cm.

As a result of measuring the radio wave absorption characteristics of the radio wave absorber of 30 MHz to 18 GHz, good absorption characteristics of 20 dB or more were obtained over the entire frequency range.

Examples 4 and 5 show that using the radio wave absorption sheet member of the present invention can produce a radio wave absorber having the same performance even when the cutting direction is different.

<Example 6>

(Corrugated board containing no electrical loss material)

The same sheet B as obtained for the planar liner in Example 1 was corrugated with a corrugator to produce a center with a height of 2.5 mm and a spacing between adjacent tops of 5 mm.

Subsequently, the same planar liner sheet B as obtained in the center and in Example 1 was bonded with a starch-based adhesive having a coating amount of 5 g / m ² , using the same collider, to prepare a single-sided corrugated sheet.

(Wave absorber)

The radio wave absorbing sheet member C obtained in Example 1 and the single-sided corrugated sheet were bonded together with a starch-based adhesive having a coating amount of 5 g / m ² so that the central side of the single-sided corrugated sheet was an adhesive portion to prepare a radio wave absorbing sheet member G.

With respect to the electromagnetic wave absorption sheet member G, the dielectric loss in the case where an electric field was applied in parallel to the longitudinal direction of the corrugated plate and when the electric field was applied in parallel to the width direction has the same measurement result as that of the electromagnetic wave absorption sheet material C obtained in Example 1. The anisotropy of the dielectric loss was very small. Moreover, this electromagnetic wave absorption sheet | seat G had flame retardance equivalent to UL94 VTM-1, and the vertical compressive strength was 3.2 kN / m.

<Example 7>

(Electric wave absorption sheet)

The sheet A of Example 1 was corrugated with a corrugator so that the direction showing the maximum dielectric loss in the plane of the sheet and the ridge of the top of the waveform were orthogonal, and the height between the height of 1 mm and the adjacent top was A 4 mm center was made.

Subsequently, the center and the planar liner sheet B of Example 1 were bonded to each other with a starch-based adhesive having a coating amount of 5 g / m ^{2 using} the same collider to prepare a radio wave absorbing sheet member H having a double-sided corrugated board structure. At this time, the sending direction (length direction) of the manufacture of the corrugated board was made to be orthogonal to the ridgeline direction of the top of the center. Table 6 shows the dielectric loss of the electromagnetic wave absorbing sheet member H when an electric field was applied in parallel to the longitudinal direction of the corrugated plate and when an electric field was applied in parallel to the width direction.

Frequency (GHz) Electric wave absorption sheet material H ratio Longitudinal direction Width direction 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 4 3.7 3.9 2.4 4.8 5 4 3.7 3.5 3.2 3.3 3.4 3.6 3.8 3.6 3.7 8.5 8.8 8.6 8 10 10 8.2 8.1 7.1 7.2 7.2 6.9 6.8 6.6 6.5 6.4 0.5 0.4 0.5 0.3 0.5 0.5 0.5 0.5 0.5 0.4 0.5 0.5 0.5 0.6 0.6 0.6

The radio wave absorption sheet | seat material H obtained as shown in Table 6 had a small anisotropy of dielectric loss. Moreover, this electromagnetic wave absorption sheet | seat H had flame retardance equivalent to UL94 V-0, planar compressive strength was 40 kPa, and the vertical compressive strength was 1.5 kN / m.

Comparative Example 1

(Center sheet)

The same sheet A as obtained in Example 1 was used as the central sheet.

(Sheet for flat liner)

The same sheet B as obtained in Example 1 was used as a sheet for planar liners.

(Electric wave absorption sheet material)

The corrugator is processed with a corrugator so that the direction showing the largest dielectric loss in the plane of the sheet with respect to the center sheet A is parallel to the ridge line of the top of the waveform, and the peak height of 2.5 mm and the distance between the neighboring tops are A 5 mm center was made.

Subsequently, the center and the planar liner sheet B were bonded to each other with a starch-based adhesive having a coating amount of 5 g / m ^{2 using} a copper collider to prepare a radio wave absorbing sheet member I having a double-sided corrugated structure. At this time, the sending direction (length direction) of the manufacture of the corrugated board was made to be orthogonal to the ridgeline direction of the top of the center.

Table 7 shows the results of measuring the dielectric loss with respect to the electromagnetic wave absorbing sheet member I when an electric field was applied in parallel to the longitudinal direction of the corrugated plate and when an electric field was applied in parallel to the width direction.

Frequency (GHz) Radio Wave Absorption Sheet Material I ratio Longitudinal direction Width direction 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 326 280 251 257 229 194 149 129 112 100 99 98 97 83 80 70 189 164 148 145 130 114 94 83 75 65 54 67 64 58 53 40 1.7 1.7 1.7 1.8 1.8 1.7 1.6 1.6 1.5 1.5 1.8 1.5 1.5 1.4 1.5 1.8

The difference in the dielectric losses in both directions was more than 30, resulting in a very large and large anisotropy.

According to the present invention, a radio wave absorbing sheet material excellent in isotropy with respect to dielectric loss characteristics can be obtained.

Moreover, the electromagnetic wave absorption sheet | seat body which can absorb the radio wave which arrives in all directions by a design of short time can be obtained.

Claims (21)

A corrugated structure in which a center and a planar liner are formed by laminating an electrical loss material-containing sheet containing an electrical loss material into a wave shape, and the electrical loss material-containing sheet has the largest dielectric strength in a plane shape plane. the dielectric loss (ε _"p) and dielectric loss (ε in the direction (v) perpendicular to the direction" ratio (ε _"p / ε" _v) of _v) in the direction (p) representing a loss of 1.2 to 4 A radio wave absorbing sheet member having phosphorus anisotropy and wave-processing the electrical loss material-containing sheet so that the direction showing the maximum dielectric loss is substantially orthogonal to the ridge line of the top of the waveform. The electromagnetic wave absorbing sheet member according to claim 1, wherein the electrical loss material-containing sheet is kneaded paper containing conductive fibers. The radio wave absorption sheet material according to claim 2, wherein the fiber length of the conductive fiber is in the range of 2 mm to 20 mm. The radio wave absorption sheet material according to claim 2, wherein the content of the conductive fiber is 0.1 to 10 mass%. The radio wave absorbing sheet material according to claim 2, wherein the electrical loss material-containing sheet further comprises a flame retardant fiber. The radio wave absorbing sheet member according to claim 2, wherein the electrical loss material-containing sheet further comprises 11 to 63.9 mass% of cellulose fibers and 36 to 88.9 mass% of a hydrous inorganic compound. The radio wave absorbing sheet member according to claim 2, wherein the kneaded paper is water-laid by a wet papermaking method using water as a medium. The radio wave absorbing sheet member according to claim 1, wherein a basis weight of the electrical loss member-containing sheet is 120 to 200 g / m ² . The radio wave absorbing sheet member according to claim 1, wherein a center height of the center of the sheet containing the electrical loss material containing sheets is 2 to 5 mm, and an interval between adjacent top portions is 4 to 15 mm. The radio wave absorption sheet member according to claim 9, wherein the center height of the center is 2.5 to 5 mm. The radio wave absorbing sheet member according to claim 1, wherein the planar liner comprises 12 to 60 mass% of cellulose fibers and 40 to 88 mass% of a hydrous inorganic compound. The radio wave absorbing sheet member according to claim 1, wherein a basis weight of said planar liner is 120 to 400 g / m ² . The radio wave absorbing sheet member according to claim 1, wherein the corrugated sheet has a structure in which a plurality of centers are laminated. The electromagnetic wave absorbing sheet member according to claim 13, wherein the plurality of laminated centers includes a center including the electrical loss material-containing sheet and a center including a sheet not containing the electrical loss material.  The radio wave absorption sheet member according to claim 1, wherein the planar compressive strength is 40 to 250 kPa.  The radio wave absorption sheet member according to claim 1, wherein the vertical compressive strength is 1.5 to 8 kN / m. An electromagnetic wave absorber comprising the electromagnetic wave absorbing sheet material according to claim 1. The electromagnetic wave absorber according to claim 17, wherein a plurality of electromagnetic wave absorbing sheet materials are laminated. The electromagnetic wave absorber according to claim 17, wherein the electromagnetic wave absorbing sheet member is assembled from a hollow three-dimensional structure having a shape selected from a wedge shape, a polygonal pyramid shape, and a polygonal column shape. 20. The radio wave absorber according to claim 19, wherein the hollow solid structure is provided on a sintered ferrite plate. The radio wave absorber according to claim 19, wherein the hollow three-dimensional structure is provided on a plate-like body formed by laminating a plurality of the radio wave absorption sheet members.