ELECTROMAGNETIC FLUX CONTROLLING MEMBER AND MOLD

The present invention relates to an electromagnetic flux controlling member including a plurality of protrusions that can be easily molded in a shape matching a mold. An electromagnetic flux controlling member of an embodiment of the present invention is an electromagnetic flux controlling member including a plurality of protrusions. At least one of the plurality of protrusions includes a piece parting transfer line.

TECHNICAL FIELD

The present invention relates to an electromagnetic flux controlling member, and a mold.

BACKGROUND ART

In wireless communications, the use of lens antennas is known as a means of transmitting more information over long distances with high efficiency. Lens antennas have the ability to control the direction of travel of electromagnetic waves, including radio waves, by converting spherical waves into plane waves, etc., and recently, they have begun to be used for electromagnetic waves with shorter wavelengths such as quasi-millimeter waves, millimeter waves and terahertz waves.

In the related art, electromagnetic flux controlling members (lenses) such as the the above-described lens antennas contain a dielectric medium such as ceramics or resin. Therefore, when electromagnetic waves are incident on the lens, they have a strong tendency to be reflected due to the difference in refractive index between air and lens.

Lenses having a structure to soften the change in refractive index are known as lenses to reduce the reflection of such electromagnetic waves. Specifically, such a lens has a plurality of protrusions protruding from the lens surface. Preferably, the plurality of protrusions has a structure such that they taper as they protrude from the surface. This allows the formation of a layer on the surface of the lens in which the ratio of air to convexity (ceramic or resin) changes gradually, i.e., a layer in which the refractive index changes gradually on the surface of the lens, thereby reducing the reflection of electromagnetic waves.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

PTL 1 discloses an antireflection structure having a plurality of protrusions as described above. Such structures are often manufactured by filling a mold with material having multiple concavities. However, because protrusions for preventing such reflections are thin, they may not match the mold when manufactured using the mold (which may result in poor transferability).

An object of the present invention is to provide an electromagnetic flux controlling member including a plurality of protrusions that can be easily molded to match the mold. In addition, another object of the present invention is to provide a mold for molding the electromagnetic flux controlling member.

Solution to Problem

An electromagnetic flux controlling member according to an embodiment of the present invention includes a plurality of protrusions. At least one of the plurality of protrusions includes a piece parting transfer line.

A mold according to an embodiment of the present invention is configured to mold an electromagnetic flux controlling member including a plurality of protrusions. At least one of a plurality of recesses corresponding to the plurality of protrusions includes two or more pieces.

Advantageous Effects of Invention

According to the present invention, it is possible to provide an electromagnetic flux controlling member including a plurality of protrusions that can be easily molded to match the mold. In addition, it is possible to provide a mold for molding the electromagnetic flux controlling member.

DESCRIPTION OF EMBODIMENTS

Electromagnetic Flux Controlling Member

FIG.1Ais a photograph showing electromagnetic flux controlling member100according to an embodiment of the present invention,FIG.1Bis a sectional view of electromagnetic flux controlling member100, andFIG.1Cis a partially enlarged bottom view of electromagnetic flux controlling member100. Note that hatching is omitted inFIG.1B. Note that inFIG.1A, electromagnetic flux controlling member100is captured diagonally above.

As illustrated inFIGS.1A and1B, electromagnetic flux controlling member100includes a plurality of protrusions110. In the present embodiment, electromagnetic flux controlling member100includes incidence surface120for entering electromagnetic waves, and emission surface130for emitting, to the outside, electromagnetic waves entered from incidence surface120.

Preferably, the material of electromagnetic flux controlling member100is resin. In addition, preferably, the material of electromagnetic flux controlling member100contains an inorganic filler in order to increase the refractive index. Preferably, the inorganic filler is 10 vol. % or greater.

In the present embodiment, each of incidence surface120and emission surface130includes the plurality of protrusions110. In addition, in the present embodiment, the plurality of protrusions110is disposed on the flat surface in incidence surface120, and the plurality of protrusions110is disposed on the convex surface in emission surface130as illustrated inFIG.1B. That is, in the present embodiment, electromagnetic flux controlling member100has a structure with protrusion110provided in incidence surface120and emission surface130of a planoconvex lens. Note that the shape of the lens provided with protrusion110is not limited to a planoconvex lens. For example, the shape of the lens provided with protrusion110may be a biconvex lens and the like. In addition, the shapes of incidence surface120and emission surface130may be appropriately set depending on how the electromagnetic waves should be controlled. For example, the curvatures of incidence surface120and emission surface130and the like may be appropriately set.

The portion where protrusion110is provided is a layer where air and the material such as the resin making up protrusion110are mixed. In this manner, the layer functions as a layer with a refractive index between the refractive index of the air and the refractive index of the material. Therefore, with protrusion110, the electromagnetic waves incident on incidence surface120and the electromagnetic waves emitted from emission surface130can be prevented from being reflected due to abrupt change of the refractive index.

The shape of protrusion110is not limited as long as the above-mentioned function can be ensured. The shape of protrusion110may be a shape (such as a columnar shape) whose size does not change even when it is separated away from the surface (the incidence surface or the emission surface) of electromagnetic flux controlling member100, or a shape whose size changes (such as a conical shape or a frustum shape). Preferably, protrusion110has a shape that becomes thinner as the distance from the surface of electromagnetic flux controlling member100increases, from a view point of softening the variation of the refractive index.

Examples of the shape of protrusion110include a rectangular shape, a columnar shape, a pyramidal shape, a conical shape, a truncated pyramidal shape, a truncated conical shape and the like. Among them, a pyramidal shape, a conical shape, a truncated pyramidal shape, and a truncated conical shape are preferable from a view point of softening the variation of the refractive index.

The size of protrusion110may be appropriately selected in accordance with the wavelength of the electromagnetic waves for which reflection is to be prevented. For example, in the case of a frequency of 300 GHz band, it suffices that in plan view, the maximum length of protrusion110is approximately 200 to 500 μm and the height of protrusion110is approximately 200 to 500 μm. In addition, in the case of a frequency of 100 GHz band, for example, it suffices that in plan view, the maximum length of protrusion110is approximately 600 to 1500 μm, and the height of protrusion110is approximately 600 to 1500 μm. In addition, preferably, the size of protrusion110is half the wavelength of the electromagnetic waves or smaller, and is the processing limit or greater.

In addition, preferably, protrusion110has a shape that does not have sides where the angle between two surfaces is 90° or smaller from a view point of increasing the mold releasability. From this view point, the protrusion preferably has a chamfered rectangular prism shape, a chamfered pyramidal trapezoidal shape, a chamfered pyramidal shape or the like. Preferably, the top surface and/or the bottom of protrusion110is chamfered. Examples of the chamfer include C-chamfer and R-chamfer.

Note that in the present embodiment, protrusion110is a quadrangular prism with chamfered eight sides as illustrated inFIGS.1A to1C.

As illustrated inFIG.1C, protrusion110includes piece parting transfer line111. Piece parting transfer line111is a line generated by transferring piece parting boundary line211provided at recess210of mold200with a shape complementary to protrusion110(seeFIG.2). Piece parting boundary line211is a boundary of a plurality of pieces200amaking up mold200. During the molding, piece parting boundary line211of mold200serves as an entrance of a loophole through which the molding material cannot pass while the gas generated from the molding material and the air in recess210and the like can pass. Note that the air and/or the gas entered from the entrance is ejected to the outside through a part between a plurality of pieces (the loophole).

Recess210corresponding to protrusion110provided with piece parting boundary line211, i.e., protrusion110provided with piece parting transfer line111, means that electromagnetic flux controlling member100has been molded without affected by the air or gas. That is, this means that protrusion110has been molded to match the shape of mold200.

It suffices that piece parting transfer line111is disposed in any of the location in protrusion110. More specifically, preferably, in plan view of protrusion110, at least a part of piece parting transfer line111is disposed inside the outer edge of protrusion110. In addition, preferably, at least a part of piece parting transfer line111is disposed at the top surface or the end of protrusion110from a view point of suppressing the influence of the air and the gas. In addition, in the case where piece parting transfer line111is disposed at the top surface of protrusion110, it is preferable that piece parting transfer line111be disposed to pass through the topmost part of the top surface.

InFIGS.1A to1C, all (100%) of the plurality of protrusions110provided in electromagnetic flux controlling member100(incidence surface120and emission surface130) include piece parting transfer line111, but electromagnetic flux controlling member100of the present embodiment is not limited to this. 80% or more of the plurality of protrusions110provided in electromagnetic flux controlling member100may include piece parting transfer line111, or 50% or more of the plurality of protrusions110may include piece parting transfer line111. Alternatively, at least one of the plurality of protrusions110may include piece parting transfer line111. Even when all of the plurality of protrusions110do not include piece parting transfer line111, a plurality of protrusions can be molded to match the mold in such a manner as to achieve the effect of preventing the reflection by reducing the influence of the air and the gas. Note that from a view point of molding protrusion110to match mold200, the larger the ratio of protrusions110including piece parting transfer line111, the more preferable.

It suffices to appropriately adjust the thickness (width) of piece parting transfer line111such that during the molding, the molding material does not escape from piece parting boundary line211while the air, the gas and the like escape. More specifically, the thickness of piece parting transfer line111may span from a visually recognizable thickness to a thickness that can be observed using devices such as optical microscopes and electron microscopes.

In the present embodiment, piece parting transfer line111extends from the end to end of electromagnetic flux controlling member100in plan view of electromagnetic flux controlling member100. In addition, in the present embodiment, in plan view, a plurality of piece parting transfer lines111parallel to each other is provided.

In electromagnetic flux controlling member100, it is preferable that one piece parting transfer line111is shared by a large number of protrusions110. Specifically, it is preferable that the plurality of protrusions110be disposed such that they are at least partially located on one piece parting transfer line111in plan view of electromagnetic flux controlling member100. In the present embodiment, in plan view, the plurality of protrusions110is disposed in a grid, and a plurality of piece parting transfer lines111parallel to each other is disposed to pass through the plurality of protrusions110.

FIG.2is a plan view of second mold230, which is a mold on incidence surface120side.FIG.3is a sectional view of recess210of second mold230. Note thatFIG.3also illustrates a cross section of protrusion110, which is formed by recess210of second mold230.FIG.4is a schematic cross-sectional view illustrating first mold220(upper side), which is a mold on the emission surface side, and second mold230(lower side), which is a mold on the incidence surface side. InFIG.4, the size of recess210and the like are increased, and hatching is omitted. Mold200is configured for molding the above-mentioned electromagnetic flux controlling member100, and has a shape complementary to electromagnetic flux controlling member100.

The material of mold200is not limited as long as it has a rigidity with which the molding material can be supplied and electromagnetic flux controlling member100can be molded, and may be appropriately selected from publicly known materials. Examples of the material of mold200include metal.

In the present embodiment, first mold220includes a curved concave surface of a shape corresponding to emission surface130. A plurality of recesses210is disposed in this curved concave surface.

In the present embodiment, second mold230includes a flat surface of a shape corresponding to incidence surface120. The plurality of recesses210is disposed at this flat surface.

The plurality of recesses210have shapes complementary to the plurality of protrusions110. Examples of the shape of recess210include a rectangular prism shape, a columnar shape, a pyramidal shape, a conical shape, a truncated pyramidal shape, a truncated conical shape and the like. In addition, the plurality of pieces200ais formed with recess210.

The size of recess210may be appropriately selected in accordance with the wavelength of the electromagnetic waves for which reflection is to be prevented. In the case of a frequency of 300 GHz band, it suffices that in plan view, the maximum length of recess210is approximately 200 to 500 μm, and the depth of recess210is approximately 200 to 500 μm. In addition, in the case of a frequency of 100 GHz band, it suffices that in plan view, the maximum length of recess210is approximately 600 to 1500 μm, and the height of recess210is approximately 600 to 1500 μm, for example. In addition, preferably, the size of recess210is half the wavelength of the electromagnetic waves or smaller, and is the processing limit or greater.

In addition, preferably, recess210has a shape that does not have sides where the angle between two surfaces is 90° or smaller from a view point of increasing the mold releasability. From this view point, preferably, recess210has a chamfered rectangular prism shape, a chamfered pyramidal trapezoidal shape, a chamfered pyramidal shape or the like. The examples of the chamfer include C-chamfer and R-chamfer.

Note that in the present embodiment, recess210is a quadrangular prism with chamfered eight sides in plan view.

Recess210is composed of two or more pieces200a. The boundary line of two pieces200ais piece parting boundary line211. In the present embodiment, one recess210is composed of two pieces200a, and accordingly recess210includes one piece parting boundary line211.

As described above, piece parting boundary line211serves as an entrance of a loophole from which the gas generated from the molding material and the air in recess210can escape during the molding. Accordingly, the molding material is appropriately supplied into recess210, and protrusion110is molded into a shape matching mold200.

It suffices that piece parting boundary line211is disposed in any of the location in recess210. More specifically, preferably, at least a part of piece parting boundary line211is disposed inside the outer edge of recess210in plan view of recess210. In addition, preferably, at least a part of piece parting boundary line211is disposed at the most depth side end or the bottom surface of recess210from a view point of the suppressing the influence of the air and the gas. In addition, in the case where piece parting boundary line211is disposed at the bottom surface of recess210, it is preferable that piece parting boundary line211be disposed to pass through the most depth side part of the bottom surface.

InFIG.4, all (100%) of recesses210provided in mold200(first mold220and second mold230) include piece parting boundary line211, but mold200of the present embodiment is not limited to this. 80% or more of recesses210provided in mold200may include piece parting boundary line211, or 50% or more of recesses210may include piece parting boundary line211. In addition, at least one of the plurality of recesses may include piece parting boundary line211. Even when all recesses210do not include piece parting boundary line211, protrusion110can be molded in a shape matching the mold in such a manner as to achieve the effect of preventing the reflection by reducing the above-described influence of the air and the gas. Note that from a view point of molding protrusion110to match the mold200, the larger the ratio of recesses210including piece parting boundary line211, the more preferable.

It suffices that the thickness (width) of piece parting boundary line211is a size through which the molding material cannot pass while the air and the gas and the like can pass during the molding. More specifically, the thickness of piece parting boundary line211may span from a visually recognizable thickness to a thickness that can be observed using devices such as optical microscopes and electron microscopes.

In the present embodiment, piece parting boundary line211extends from the end to end of mold200in plan view of mold200. In addition, in the present embodiment, a plurality of piece parting boundary lines211are parallel to each other.

In mold200, it is preferable that a large number of recesses210share one piece parting boundary line211. That is, in plan view of mold200, the plurality of recesses210is disposed such that they are at least partially located on one piece parting boundary line211. In the present embodiment, in plan view, the plurality of recesses210is disposed in a grid, and a plurality of piece parting boundary lines211parallel to each other is disposed to pass through the plurality of recesses210.

Molding Procedure

An example of a procedure of molding electromagnetic flux controlling member100is described below.

First, mold200is prepared. More specifically, first mold220and second mold230are fixed at predetermined positions. Next, the molding material is emitted to the cavity between first mold220and second mold230. At this time, the gas generated from the molding material and the air in recess210are ejected from piece parting boundary line211. In this manner, protrusion110of electromagnetic flux controlling member100is easily molded to match mold200.

Next, the molding material is solidified by cooling it under pressure. Next, first mold220and second mold230are opened, and the molded electromagnetic flux controlling member100is removed. In this manner, electromagnetic flux controlling member100can be obtained.

Effects

The electromagnetic flux controlling member according to the present embodiment can easily mold a protrusion that can suppress the reflection of electromagnetic waves in a shape matching the mold. In addition, the mold according to the present embodiment can mold the above-mentioned electromagnetic flux controlling member.

INDUSTRIAL APPLICABILITY

The electromagnetic flux controlling member and the mold according to the present invention is suitable for performing communication using electromagnetic waves and the like while reducing the influence of the reflection.

REFERENCE SIGNS LIST