JP2009259470A - Key sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce radiation of electromagnetic waves from an electronic apparatus to the outside by absorbing the electromagnetic waves or reduce malfunction in a semiconductor element, relating to a key sheet comprising a base sheet to be placed on a circuit board while supporting a push operation part afloat. <P>SOLUTION: An electromagnetic wave absorbing part is provided which contains an electromagnetic wave absorbing material 13 over the entire base sheet 12, or at a floating support part 12b or a leg part 12d, or on the surface of the base sheet. Further, by employing a flat electromagnetic wave absorbing material 13 comprising powder, a frequency range which can be coped with is widened. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a key sheet for a push button switch used in various electronic devices such as a portable information terminal such as a mobile phone and a PDA, an in-vehicle AV device, a remote controller, and a personal computer, and more particularly to a key sheet that absorbs or reflects electromagnetic waves.

  2. Description of the Related Art Pushbutton switches of various electronic devices such as mobile phones and AV devices have a structure in which pushbuttons (key tops) for performing an input operation by pressing are exposed from an operation opening formed in the casing of the electronic device. Many. Specifically, a key sheet including a key top and a base sheet on which the key top is placed is placed on a circuit board on which a contact switch is arranged, and the casing is covered from the surface side of the key sheet, thereby the key sheet. It is customary to incorporate in the housing.

By the way, in an electronic device whose functionality is increasing, a structure is provided in which a conductive layer is provided inside a casing made of resin to reflect and shield electromagnetic waves (Patent Document 1). This structure prevents electromagnetic waves generated from semiconductor elements mounted on the circuit board from radiating to the outside of the electronic device, and prevents electromagnetic waves from entering the electronic device from the outside of the electronic device. A semiconductor element incorporated in an electronic device or a semiconductor element included in another electronic device outside the electronic device is prevented from malfunctioning.
Japanese Patent Laid-Open No. 2002-359489

However, in an electronic device including a key sheet, an operation opening is formed in the housing. Therefore, even if a conductive layer is provided in the housing, electromagnetic waves pass through the operation opening, so that the countermeasure against electromagnetic waves of the electronic device is insufficient.
In addition, semiconductor devices are more susceptible to electromagnetic waves generated with increased processing capacity and increased processing capacity, and there is a risk that semiconductor devices other than the source may malfunction due to electromagnetic waves generated inside electronic devices. It is growing.
Furthermore, the Voluntary Control Council for Interference from Information Processing Equipment (VCCI) cooperates in the self-regulation of jamming waves that are generated from information processing equipment and electronic office equipment and interfere with radio and television receivers. Looking for.

  The present invention has been made based on this background. That is, an object of the present invention is to provide a key sheet that reduces the radiation of electromagnetic waves to the outside of an electronic device or prevents malfunction of a semiconductor element.

  In order to achieve the above object, a key sheet having a base sheet that floats and supports the pressing operation unit and is placed on the circuit board, the key sheet comprising an electromagnetic wave absorbing unit containing an electromagnetic wave absorbing material in the base sheet Provide a sheet.

  Since the base sheet has an electromagnetic wave absorbing part containing an electromagnetic wave absorbing material, the electromagnetic wave generated from the semiconductor element mounted on the circuit board is absorbed by the electromagnetic wave absorbing part, and the electromagnetic wave is radiated to the outside of the electronic device or adjacent thereto. Radiation to the semiconductor element can be reduced or prevented, and an electronic device with improved electromagnetic wave countermeasures can be obtained.

  The key sheet of the present invention as described above can be roughly divided into four forms.

The form of the first key sheet is that the pressing operation portion is a resin key top, the base sheet is a translucent pedestal portion that fixes the resin key top, and a floating support portion that supports the pedestal portion so as to be capable of being pressed and displaced. And a leg portion that supports the floating support portion on the circuit board, and an electromagnetic wave absorbing portion is provided on the leg portion.
Since the electromagnetic wave absorbing portion is provided in the leg portion, the electromagnetic wave generated from the semiconductor element mounted on the circuit board can be reduced from being emitted to the outside of the electronic device through the leg portion. Further, the electromagnetic wave is absorbed by the leg part with respect to the semiconductor element adjacent to the electromagnetic wave generation source and the leg part, and malfunction of the semiconductor element can be made difficult to occur.

The form of the second key sheet is that the pressing operation portion is a resin key top, the base sheet is a translucent pedestal portion that fixes the resin key top, and a floating support portion that supports the pedestal portion so as to be capable of being pressed and displaced And a leg portion for supporting the floating support portion on the circuit board, and an electromagnetic wave absorbing portion is provided on the floating support portion.
Since the electromagnetic wave absorbing part is provided in the floating support part, the floating support part can absorb the electromagnetic wave generated from the semiconductor element mounted on the circuit board and reduce the emission of electromagnetic waves to the outside of the electronic device through the floating support part. can do.

In the third key sheet, the base sheet is formed of a rubber-like elastic body, and an electromagnetic wave absorbing portion is provided on the entire base sheet.
Since the electromagnetic wave absorbing portion is provided on the entire base sheet, the base sheet can absorb electromagnetic waves generated from the semiconductor elements mounted on the circuit board, and the base sheet covers the entire operation opening of the housing. Radiation of electromagnetic waves to the outside of the electronic device can be suppressed. In addition, if the base sheet has a portion that goes in the crossing direction with respect to the base sheet plane such as a leg portion, it is possible to suppress electromagnetic waves received by other semiconductor elements existing across the portion of the base sheet, It is possible to prevent malfunction of a semiconductor element different from the electromagnetic wave generation source inside the electronic device.

In the fourth key sheet, the pressing operation part is a resin key top, the base sheet is a rubber-like elastic body, and a coating layer is provided on the surface, and the electromagnetic wave absorbing part is provided in the coating layer. It is what.
Since the base sheet is provided with a coating layer having an electromagnetic wave absorbing portion on the surface of the rubber-like elastic body, the coating layer provided on the surface of the base sheet can absorb electromagnetic waves generated from a semiconductor element mounted on a circuit board. It is possible to reduce the emission of electromagnetic waves from the operation opening of the housing to the outside of the electronic device.

For such a key sheet, a layered electromagnetic wave reflecting portion can be provided on the surface side of the base sheet. Since the layered electromagnetic wave reflection part is provided on the surface side of the base sheet, even if there is an electromagnetic wave that cannot be absorbed by the electromagnetic wave absorption part, it can be reflected by the electromagnetic wave reflection part, further suppressing the emission of electromagnetic waves to the outside of electronic equipment can do.
The electromagnetic wave reflecting portion can be provided directly or indirectly with respect to the surface of the electromagnetic wave absorbing portion, and when the key sheet is provided with a key top, it can be provided on the bottom surface of the key top. The electromagnetic wave reflection part can be formed of a conductive material, for example, a metal, a composite oxide conductor, a conductive polymer, a conductive powder-containing resin, or the like. These volume resistivity is preferably 1.0 Ω · cm or less.
If the electromagnetic wave reflection part is a metal thin plate, not only can the electromagnetic wave be reliably reflected, but the electromagnetic wave absorption part can be protected. The thickness of the metal thin plate is preferably 50 μm to 2000 μm.
If the electromagnetic wave reflection part is made of a metal mesh, the electromagnetic wave shielding effect is relatively weaker than that of a metal thin plate, but it has a sufficient shielding effect practically and can transmit light. An illuminated key sheet can be obtained.

In addition, the electromagnetic wave reflecting portion may include a complex oxide conductor and be translucent. Since “electromagnetic waves” are classified into radio waves, light, X-rays, and γ rays from the longer wavelength, if the electromagnetic wave reflection part is made translucent, it should be an electromagnetic wave reflection part that reflects radio waves and transmits light. Can do.
Therefore, when the entire surface of the base sheet is covered with a translucent radio wave reflection layer, the radio wave can be reflected and illuminated by the surface of the base sheet.

  About the electromagnetic wave reflection part, the surface of the surface facing the circuit board may be an uneven surface. Since the surface on the side facing the circuit board is an uneven surface, electromagnetic waves generated from the semiconductor elements mounted on the circuit board can be made difficult to be regularly reflected toward the circuit boards, and electromagnetic waves transmitted to the semiconductor elements can be reduced. Can do.

  The base sheet can be provided with a through hole through which light from an illumination light source mounted on the circuit board is passed, and an electromagnetic wave reflecting portion filled with a translucent resin containing a composite oxide conductor can be provided in the through hole. The base sheet is provided with a through-hole that allows light from the illumination light source mounted on the circuit board to pass therethrough, and an electromagnetic wave reflecting portion filled with a translucent resin containing a composite oxide conductor is provided in the through-hole. In addition, since the electromagnetic waves are reflected by the through holes, it is possible to prevent the electromagnetic waves from being emitted to the outside through the through holes.

  Alternatively, the base sheet can be provided with a through hole through which light from the illumination light source mounted on the circuit board is passed, and a metal mesh that closes the through hole can be provided. The base sheet is provided with a through hole that allows light from the illumination light source mounted on the circuit board to pass through, and a metal mesh that closes the through hole is provided, so that the light can be illuminated through the through hole. Since the light is reflected, it is possible to prevent electromagnetic waves from being emitted to the outside through the through holes.

A polymer coating layer can be further provided on at least either the front surface side or the back surface side of the base sheet.
Since the electromagnetic wave absorbing part has a property of becoming brittle when the filling amount of the electromagnetic wave absorbing material is increased, if a polymer coating layer is provided on at least one of the front side and the back side of the base sheet, the electromagnetic wave absorbing material is prevented from falling off. The electromagnetic wave absorbing part can be protected. And the mechanical strength of a base sheet can be raised. Such a polymer coating layer can be formed of a resin film or a coating layer. In particular, if it is a resin film, it can be made difficult to break even if the polymer coating layer is repeatedly deformed.

Furthermore, a light guide plate can be provided on the outermost surface of the base sheet. When an electromagnetic wave absorbing material is contained, the translucency deteriorates and it becomes difficult to illuminate the key sheet with backlight light. However, by providing a light guide plate, the light can be guided by the light guide plate to illuminate the key sheet. .
A low refractive layer can be provided between the base sheet and the light guide plate. By providing a low refraction layer, light incident from the side surface can be totally reflected at the interface between the light guide plate and the low refraction layer, and the light is guided to a location farther away from the light source than when no low refraction layer is provided. be able to. In addition, even in the vicinity of the light source, light leakage can be reduced and the degree of illumination can be increased.

The electromagnetic wave absorbing material is a flat powder, and a key sheet having an electromagnetic wave absorbing portion in which the flat powder is oriented along the surface direction of the base sheet can be obtained.
Since the flat powder of the electromagnetic wave absorber is oriented along the surface direction of the base sheet, it is easy to absorb the electromagnetic wave propagating in the direction perpendicular to the surface of the base sheet. Electromagnetic waves radiated to the outside of the device can be reduced. Furthermore, the frequency band of the electromagnetic wave to be absorbed can be expanded, and the magnetic permeability and magnetic loss of the electromagnetic wave absorbing portion can be increased. Therefore, electromagnetic waves can be efficiently absorbed, radiation of electromagnetic waves to the outside of the electronic device can be reduced, and malfunction of semiconductor elements inside the electronic device can be made difficult to occur.

  In the key sheet of the present invention, the electromagnetic wave absorbing material can be a soft magnetic powder. This is because the soft magnetic material has a high magnetic permeability and a large magnetic loss, so that it can efficiently absorb electromagnetic waves. For example, Mn-Zn ferrite powder, Fe-Si alloy powder, Fe-Si-Al alloy (Sendust) powder, Fe-Ni alloy (Permalloy) powder, Mn-Zn ferrite powder, Ni-Zn ferrite powder Fe-Si-Cr alloy (electromagnetic stainless steel) powder or the like can be used.

  According to the key sheet of the present invention, the electromagnetic wave absorbing portion provided in the base sheet absorbs the electromagnetic wave generated from the semiconductor element mounted on the circuit board, and the electromagnetic wave is radiated from the operation opening of the housing to the outside of the electronic device. Can be reduced. In addition, electromagnetic waves radiated inside the electronic device can be reduced, and malfunction of the semiconductor element inside the electronic device can be prevented.

  Further, by mounting the key sheet of the present invention on an electronic device, it is not necessary to attach another electromagnetic wave absorbing component on the key sheet, and an electromagnetic wave countermeasure can be taken without increasing the bulk capacity of the electronic device.

The present invention will be described for each of various embodiments with reference to the drawings. In each embodiment, as shown in FIG. 1, the present invention is applied to a key sheet that is incorporated into a housing 2 of a mobile phone 1.
In addition, about the structure which is common in each embodiment, the same code | symbol is attached | subjected and duplication description about a common structure, an effect, a manufacturing method, a raw material, etc. is abbreviate | omitted.

First Embodiment [FIGS. 1 and 2]:
FIG. 1 is a plan view of a mobile phone 1 including the key sheet 3 of the first embodiment, and FIG. As shown in FIG. 2, the key sheet 3 is attached with its outer edge sandwiched in a pressed state between the holding portion 2 a protruding from the inner surface of the housing 2 in the mobile phone 1 and the circuit board 4. The key sheet 3 includes a plurality of key top portions 5 and a base sheet portion 6 as “pressing operation portions”. That is, the key top part 5 is a key operation part 3 which is a pressing operation part, and the base sheet part 6 is a base sheet.

  An operation opening 2b that exposes the key top portion 5 of the key sheet 3 is formed in the casing 2, and the operation opening 2b is partitioned for each key top portion 5 by a partition bar 2c.

  The circuit board 4 includes a metal disc spring 7 as a contact switch on the surface facing the key sheet 3, and a semiconductor element 8 is mounted on the front and back surfaces.

  The key top portion 5 is formed of a rubber-like elastic body filled with an electromagnetic wave absorbing material 9 in the form of a bulk powder as an “electromagnetic wave absorbing portion”, and is projected in a long cylindrical shape with respect to the operation surface side of the base sheet portion 6. Yes. On the surface of the key top portion 5, a print layer (not shown) representing display elements such as numbers and characters is applied.

  The base sheet portion 6 is also formed of a rubber-like elastic body filled with the electromagnetic wave absorbing material 9 as an “electromagnetic wave absorbing portion”. Around the key top portion 5 in the base sheet portion 6, a floating support portion 6 a that allows the key top portion 5 to be displaced by pressing is provided. On the back surface facing the circuit board 4, a pusher portion 6 b is formed in a columnar shape for each key top portion 5, and this pusher portion 6 b is a portion that presses the metal disc spring 7 of the circuit board 4. Further, on the back surface, a leg portion 6 c is projected from the entire outer periphery and between the adjacent key top portions 5, and the tip of the leg portion 6 c is in contact with the surface of the circuit board 4.

Here, the material of each member constituting the key sheet 3 will be described.
The material of the rubber-like elastic body is preferably rubber having high resilience or a thermoplastic elastomer. For example, for rubber, natural rubber, silicone rubber, ethylene propylene rubber, butadiene rubber, isoprene rubber, chloroprene rubber, urethane rubber, etc. can be used. , Ester thermoplastic elastomer, urethane thermoplastic elastomer, amide thermoplastic elastomer, butadiene thermoplastic elastomer, ethylene-vinyl acetate thermoplastic elastomer, fluororubber thermoplastic elastomer, isoprene thermoplastic elastomer, chlorinated polyethylene A thermoplastic elastomer can be used. Of these, silicone rubber is preferable in consideration of the low temperature dependence, and styrene-based thermoplastic elastomer and ester-based thermoplastic elastomer are preferable in consideration of durability.

The material of the electromagnetic wave absorber 9 is preferably soft magnetic powder. For example, Mn-Zn ferrite powder, Fe-Si alloy powder, Fe-Si-Al alloy (Sendust) powder, Fe-Ni alloy (Permalloy) powder, Mn-Zn ferrite powder, Ni-Zn ferrite powder Fe-Si-Cr alloy (electromagnetic stainless steel) powder or the like can be used. Among these, the Fe—Ni-based alloy (permalloy) powder is preferable because the alloy is sticky, and thus a powder with high flatness can be easily produced, so that high electromagnetic wave absorption characteristics can be obtained. From the balance of cost and characteristics, it is preferable to use Fe—Si—Cr alloy (electromagnetic stainless steel) powder or Fe—Si—Al alloy (Sendust) powder.
The content ratio of such an electromagnetic wave absorbing material to the rubber-like elastic body is preferably 5 vol% to 80 vol% from the thermal characteristics and flexibility of the molded body. If the content of the electromagnetic wave absorbing material is less than 5 vol%, the dispersed state is too discrete to effectively absorb the electromagnetic wave, and if it exceeds 80 vol%, the flexibility of the rubber-like elastic body is lost and the key top portion 5 is pressed. It may be difficult to operate. A more preferable content ratio is 30 vol% to 60 vol%. If it is 30% or more, the electromagnetic wave absorption characteristics can be improved, and if it is 60 vol% or less, the rubber-like elastic body can have good moldability.

Next, a method for manufacturing the key sheet 3 will be described.
First, the electromagnetic wave absorbing material 9 is added and kneaded to an uncured rubber composition using a kneader to obtain a rubber composition in which the electromagnetic wave absorbing material 9 is uniformly dispersed. Next, when this rubber composition is molded and cured with a molding die for the key sheet 3, a rubber molded body in which the key top portion 5 and the base sheet portion 6 are integrated and the electromagnetic wave absorbing material 9 is uniformly dispersed is obtained. Finally, a key layer 3 can be obtained by applying a printed layer representing a display element on the surface of the key top portion 5.

The operation and effect of the key sheet 3 of this embodiment will be described.
According to the key sheet 3, since the base sheet portion 6 is an “electromagnetic wave absorbing portion”, the base sheet portion 6 absorbs electromagnetic waves generated from the semiconductor element 8 mounted on the circuit board 4, and the operation opening of the housing 2 is performed. It is possible to reduce the emission of electromagnetic waves from 2b to the outside of the mobile phone 1. Furthermore, internal electromagnetic waves in the mobile phone 1 can also be reduced, and malfunction of other semiconductor elements 8 mounted on the circuit board 4 can be made difficult to occur. Therefore, it can be set as the mobile telephone 1 which improved the electromagnetic wave countermeasure.

  Moreover, it is not necessary to attach an electromagnetic wave absorbing member in addition to the key sheet 3, and an electromagnetic wave countermeasure can be taken without increasing the bulk capacity of the mobile phone 1.

Second Embodiment [FIG. 3]:
A cross-sectional view of the key sheet 10 of the second embodiment is shown in FIG. The key sheet 10 of the second embodiment is different from the key sheet 3 of the first embodiment in that it includes a resin key top 11 as a “pressing operation unit”, and a base sheet 12 made of a material different from that of the resin key top 11. It is a point equipped with.

  The resin key top 11 is made of a hard resin and is formed in a long cylindrical shape. An annular flange that protrudes outward is provided at the bottom end. On the bottom surface of the resin key top 11, a print layer (not shown) representing the display element is applied.

The base sheet 12 is formed of a rubber-like elastic body filled with a flat powder electromagnetic wave absorbing material 13, and the whole is an “electromagnetic wave absorbing portion”. On the surface of the base sheet 12, a pedestal portion 12a is projected, and the resin key top 11 is fixed to the pedestal portion 12a by an adhesive not shown. A floating support portion 12b is provided around the pedestal portion 12a to support the pedestal portion 12a so as to be capable of being pressed and displaced. On the back surface of the base sheet 12, a pusher portion 12 c is formed in a columnar shape for each pedestal portion 12 a, and this pusher portion 12 c is a portion that presses the metal disc spring 7 of the circuit board 4. Further, a leg portion 12 d is projected between the entire outer periphery and adjacent pedestal portions 12 a, and the tip of the leg portion 12 d is in contact with the surface of the circuit board 4.
Unlike the electromagnetic wave absorber 9 of the first embodiment, the electromagnetic wave absorber 13 is a flat powder. The electromagnetic wave absorber 13 filled in the pedestal portion 12a and the floating support portion 12b is oriented along the surface direction of the base sheet 12, and the electromagnetic wave absorber 13 filled in the leg portion 12d is the surface of the base sheet 12. It is oriented in the straight direction, that is, toward the tip of the leg 12d.

Next, a method for manufacturing the key sheet 10 will be described.
First, the electromagnetic wave absorber 13 is added and kneaded to an uncured rubber composition using a kneader to obtain a rubber composition in which the electromagnetic wave absorber 13 is uniformly dispersed. Next, when this rubber composition is molded and cured with a molding die of the base sheet 12, the base sheet 12 in which the electromagnetic wave absorber 13 is uniformly dispersed is obtained. Finally, the key sheet 14 can be obtained by fixing the resin key top 11 separately injection-molded and having a printed layer representing the display element on the back surface to the pedestal portion 12a with an adhesive.
The molding die of the base sheet 12 is provided with a relief groove on the tip end side of the cavity for molding the leg portion 12d. When the rubber composition is molded and cured, the rubber composition is removed from the cavity of the leg portion 12d. By utilizing the flow into the clearance groove, the flat powder electromagnetic wave absorbing material 13 filled in the leg portion 12d can be oriented along the tip direction of the leg portion 12d. Further, by utilizing the fact that the rubber composition flows in the surface direction of the base sheet 12, the flat powder electromagnetic wave absorbing material 13 filled in the pedestal portion 12 a and the floating support portion 12 b is arranged along the surface direction of the base sheet 12. Can be oriented.

According to the key sheet 10, the base sheet 12 absorbs electromagnetic waves generated from the semiconductor elements 8 mounted on the circuit board 4 because the base sheet 12 is an “electromagnetic wave absorber”, as in the key sheet 3 of the first embodiment. Thus, the emission of electromagnetic waves from the operation opening 2b of the housing 2 to the outside of the mobile phone 1 can be reduced. Furthermore, internal electromagnetic waves in the mobile phone 1 can also be reduced, and malfunction of other semiconductor elements 8 mounted on the circuit board 4 can be made difficult to occur. Therefore, it can be set as the mobile telephone 1 which improved the electromagnetic wave countermeasure.
Moreover, it is not necessary to attach an electromagnetic wave absorbing member in addition to the key sheet 10, and an electromagnetic wave countermeasure can be taken without increasing the bulk capacity of the mobile phone 1.

In the key sheet 10, the characteristics of the flat powder can be utilized to the maximum by using the electromagnetic wave absorber 13 that is a flat powder. That is, when a soft magnetic metal powder is used for the electromagnetic wave absorber 13, the electromagnetic wave absorber contributes to the absorption of the electromagnetic wave because the electromagnetic wave is incident only on the surface of the soft magnetic metal powder due to the skin effect due to the eddy current when the electromagnetic wave is incident. This is because the volume ratio of 13 is relatively low, but electromagnetic waves can be efficiently absorbed by setting the thickness of the soft magnetic metal powder to the skin effect or less. Further, by using the flat electromagnetic wave absorbing material 13, a frequency range that can be taken can be broadened. In other words, in addition to the magnetic loss due to the crystal structure of the magnetic powder, there is a magnetic loss due to the magnetic anisotropy due to the shape anisotropy of the powder. This is because the frequency can be widened.
Thus, the key sheet 10 can efficiently absorb electromagnetic waves, and the semiconductor elements 8 and 8 mounted close to each other with the legs 12d sandwiched on the surface of the circuit board 4 are also affected by the electromagnetic waves. It can be made difficult to receive.

  Further, since the key sheet 10 is provided with the resin key top 11 made of hard resin, the operation load during the pressing operation is not alleviated, and the accurate operation load of the metal disc spring 7 can be transmitted to the operator. Can get a clear click feeling. Further, the resin key top 11 can be provided with a decorative layer such as a metal plating layer or a coating layer, so that the key sheet 10 with high design can be realized.

First Modification of Second Embodiment [FIG. 4]:
FIG. 4 shows a cross-sectional view of a key sheet 14 that is a first modification of the second embodiment. In the key sheet 14, a polymer coating layer 15 made of an insulating coating layer is provided on the back surface of the base sheet 12.
The material of the polymer coating layer 15 is preferably excellent in bending resistance, and in addition to the coating layer used in this modification, a resin film is preferable. For example, in the case of a coating layer, urethane paint, epoxy paint, imide paint, acrylic paint, fluorine paint, silicone paint, etc. can be used. For resin films, for example, polyethylene terephthalate film, polybutylene terephthalate film Polycarbonate film, polyimide film, polyurethane film, polyethylene film, polypropylene film and the like can be used.
In this way, the back surface of the base sheet 12 that has become brittle due to the filling of the electromagnetic wave absorbing material 13 can be protected, and the back surface of the base sheet 12 can be made difficult to chip. Furthermore, it is possible to prevent the electromagnetic wave absorber 13 from dropping on the circuit board 4, and an accurate pressing operation can be realized.
Further, since the insulating polymer coating layer 15 covers the back surface of the base sheet 12, even if the base sheet 12 is conductive and filled with the conductive electromagnetic wave absorber 13, the base sheet 12 Contact with the circuit on the circuit board 4 can be prevented, and circuit leakage due to the conductive base sheet 12 can be prevented.

Second Modification of Second Embodiment [FIG. 5]:
FIG. 5 shows a cross-sectional view of a key sheet 16 which is a second modification of the second embodiment. In the key sheet 16, a polymer coating layer 17 made of a translucent coating layer is provided on the surface of the base sheet 12.
If it does in this way, the surface of the base sheet 12 which became weak by filling of the electromagnetic wave absorber 13 can be protected, and the surface of the base sheet 12 can be made difficult to chip.
Moreover, since the translucent polymer coating layer 17 covers the surface of the base sheet 12, the polymer coating layer 17 can be used as the light guide layer of the base sheet 12. For example, if a light source is provided on the side surface of the base sheet 12, light can be guided to the surface side of the base sheet 12 by the polymer coating layer 17, and the surface of the base sheet 12 and the resin key top 11 can be illuminated.

Third modification of the second embodiment (FIG. 6):
FIG. 6 shows a cross-sectional view of a key sheet 18 that is a third modification of the second embodiment. In the key sheet 18, a polymer coating layer 19 made of a resin film is provided on the surface of the base sheet 12, and a polymer coating layer 20 made of a resin film is provided on the back surface, and the entire base sheet 12 is covered from the front and back by the polymer coating layers 19 and 20. It has a sandwich structure.
In this way, the front and back surfaces of the base sheet 12 can be made difficult to chip, and the mechanical strength of the base sheet 12 can be increased. Further, the entire base sheet 12 can be sealed with the polymer coating layers 19 and 20, and the electromagnetic wave absorber 13 can be completely prevented from falling off from the base sheet 12. Since the polymer coating layers 19 and 20 are made of a resin film, even if the polymer coating layers 19 and 20 are repeatedly deformed during the pressing operation, the polymer coating layers 19 and 20 are hardly damaged and can be made to have high durability.
Further, if the polymer coating layer 20 covering the back surface of the base sheet 12 is made insulating like the key sheet 14 of the first modification, circuit leakage due to the conductive base sheet 12 can be prevented, and the second modification If the polymer coating layer 19 covering the surface of the base sheet 12 is made translucent in the same manner as the key sheet 16 of the example, the surface of the base sheet 12 and the resin key top 11 can be illuminated.

Third Embodiment [FIGS. 7 and 8]:
A sectional view of the key sheet 21 according to the third embodiment is shown in FIG. 7, and an exploded plan view thereof is shown in FIG. The key sheet 21 according to the third embodiment is different from the key sheet 10 according to the second embodiment in that the base sheet 22 is not the entirety but a part thereof is provided with an “electromagnetic wave absorber”.

  In the base sheet 22, a pedestal portion 22a for fixing the resin key top 11 and a pusher portion 22c for pressing the metal disc spring 7 of the circuit board 4 are formed of a translucent rubber-like elastic body. And the floating support part 22b which supports the base part 22a so that a press displacement is possible, and the leg part 22d which contact | connects the circuit board 4 are formed with the rubber-like elastic body with which the electromagnetic wave absorption material 9 was filled, and become an "electromagnetic wave absorption part."

Next, a method for manufacturing the key sheet 21 will be described.
First, the electromagnetic wave absorbing material 9 is added and kneaded to an uncured rubber composition using a kneader to obtain a rubber composition in which the electromagnetic wave absorbing material 9 is uniformly dispersed. Next, this rubber composition is molded and cured by a molding die for molding the floating support portion 22b and the leg portion 22d of the base sheet 22. After that, the molded floating support portion 22b and the leg portion 22d are inserted into the molding die of the base sheet 22, and the base portion 22a and the pusher portion 22c are molded and cured with a light-transmitting rubber composition portion to obtain the base sheet 22. . Finally, the key sheet 21 can be obtained by fixing the resin key top 11 separately injection-molded and having a printed layer representing the display element on the back surface to the pedestal portion 22a with an adhesive.

According to the key sheet 21, since the floating support portion 22 b and the leg portion 22 d of the base sheet 22 are “electromagnetic wave absorbing portions”, electromagnetic waves generated from the semiconductor element 8 mounted on the circuit board 4 are transmitted to the floating support portion 22 b and the leg portions. It is possible to reduce the electromagnetic wave radiated from the operation opening 2b of the housing 2 to the outside of the mobile phone 1 by being absorbed by the portion 22d. Furthermore, internal electromagnetic waves in the mobile phone 1 can also be reduced, and malfunction of other semiconductor elements 8 mounted on the circuit board 4 can be made difficult to occur. Therefore, it can be set as the mobile telephone 1 which improved the electromagnetic wave countermeasure.
Moreover, it is not necessary to attach an electromagnetic wave absorbing member in addition to the key sheet 21, and an electromagnetic wave countermeasure can be taken without increasing the bulk capacity of the mobile phone 1.

  Since the pedestal portion 22a of the base sheet 22 is translucent, the backlight light from the light source mounted on the circuit board 4 can pass through the pedestal portion 22a and reach the resin key top 11, and the resin key top 11 is backed. It can be illuminated by light.

Fourth Embodiment [FIGS. 9 and 10]:
FIG. 9 shows a cross-sectional view of the key sheet 23 of the fourth embodiment, and FIG. 10 shows an exploded plan view thereof. The key sheet 23 of the fourth embodiment is different from the key sheet 10 of the second embodiment in the configuration of the base sheet 24. The remaining configuration is the same as that of the key sheet 10.

  The base sheet 24 includes a pedestal portion 24 a that fixes the resin key top 11, a floating support portion 24 b that supports the pedestal portion 24 a so that it can be pressed and displaced, and a pusher portion 24 c that presses the metal disc spring 7 of the circuit board 4. It is made of a light rubber-like elastic body. The leg portion 24 d in contact with the circuit board 4 is formed of a rubber-like elastic body filled with the electromagnetic wave absorbing material 9 as an “electromagnetic wave absorbing portion”.

Next, a method for manufacturing the key sheet 23 will be described.
First, the electromagnetic wave absorbing material 9 is added and kneaded to an uncured rubber composition using a kneader to obtain a rubber composition in which the electromagnetic wave absorbing material 9 is uniformly dispersed. Next, this rubber composition is molded and cured in a molding die for molding the leg portions 24 d of the base sheet 24. Thereafter, the molded leg portion 22d is inserted into a molding die of the base sheet 24, and the base portion 24a, the floating support portion 24b, and the pusher portion 24c are molded and cured with a light-transmitting rubber composition portion to obtain the base sheet 24. . Finally, the key sheet 23 can be obtained by fixing the resin key top 11 separately injection-molded and having a printed layer representing a display element on the back surface to the pedestal portion 24a with an adhesive.

According to the key sheet 23, since the leg portion 24 d of the base sheet 24 is an “electromagnetic wave absorbing portion”, the leg portion 24 d absorbs electromagnetic waves generated from the semiconductor element 8 mounted on the circuit board 4, and Radiation of electromagnetic waves from the operation opening 2b to the outside of the mobile phone 1 can be reduced. Furthermore, internal electromagnetic waves in the mobile phone 1 can also be reduced, and malfunction of other semiconductor elements 8 mounted on the circuit board 4 can be made difficult to occur. Therefore, it can be set as the mobile telephone 1 which improved the electromagnetic wave countermeasure.
Further, it is not necessary to attach an electromagnetic wave absorbing member in addition to the key sheet 23, and the electromagnetic wave countermeasure can be taken without increasing the bulk capacity of the mobile phone 1.

  Since the pedestal 24a and the floating support 24b of the base sheet 24 are translucent, the backlight can pass through the pedestal 24a and the floating support 24b to reach the key sheet 11, and the resin key top 11 Can be brightly illuminated.

  Since the electromagnetic wave absorber 9 is not filled in the floating support portion 24b, the pressing load can be reduced compared with the key sheet constituting the floating support portion by the electromagnetic wave absorption portion, and the press operability of the resin key top 11 is improved. Can do.

Fifth Embodiment (FIG. 11):
A cross-sectional view of the key sheet 25 of the fifth embodiment is shown in FIG. The key sheet 25 of the fifth embodiment is different from the key sheet 10 of the second embodiment in a configuration including a thin metal plate 26. The remaining configuration is the same as that of the key sheet 10.

  The metal thin plate 26 has a property of reflecting electromagnetic waves and functions as an “electromagnetic wave reflecting portion”. The thin metal plate 26 is adhered and fixed so as to follow the surface of the base sheet 12. The thickness of the thin metal plate 26 is preferably 50 μm to 2000 μm.

The material of the metal thin plate 26 is preferably a conductive metal. For example, gold, silver, copper, iron, stainless steel, nickel, aluminum, chromium, tin, zinc and the like can be used. These metals can be used in the form of a metal thin film or a wire mesh, in addition to the metal thin plate used in this embodiment.
In the present embodiment, the metal thin plate 26 is used as the “electromagnetic wave reflecting portion” for reflecting the electromagnetic wave. However, other members than the metal thin plate 26 may have a property of reflecting the electromagnetic wave. Can be used.
Such other members need to have a volume resistivity of 1.0 Ω · cm or less, and other than metals, composite oxide conductors, conductive polymers, conductive powder-containing resins, and the like are suitable. . An example of the composite oxide conductor is indium-tin oxide (ITO). Examples of the conductive polymer include polyacetylene, polypyrrole, polythiophene, polyaniline, poly (paraphenylene), poly (paraphenylenevinylene), and derivatives thereof. Examples of the conductive powder-containing resin include those in which an insulating resin is filled with a powder made of the aforementioned metal or composite oxide conductor, carbon, or the like. The powder may be in the form of fibers or lumps.

Next, a method for manufacturing the key sheet 25 will be described.
First, the electromagnetic wave absorber 13 is added and kneaded to an uncured rubber composition using a kneader to obtain a rubber composition in which the electromagnetic wave absorber 13 is uniformly dispersed. Next, the metal thin plate 26 is drawn into the same shape as the surface of the base sheet 12 using a jig or a mold, and an adhesive is applied to the fixing surface of the base sheet 12. Then, the metal thin plate 26 is inserted into the molding die of the base sheet 12, and the rubber composition to which the electromagnetic wave absorbing material 13 is added is molded and cured by the molding die of the base sheet 12. In this way, the base sheet 12 in which the metal thin plate 26 is integrated and the electromagnetic wave absorber 13 is uniformly dispersed is obtained. Finally, the key sheet 25 can be obtained by fixing the resin key top 11 separately molded by injection molding and having the printed layer representing the display element on the back surface to the metal thin plate 26 covering the pedestal portion 12a with an adhesive.

According to the key sheet 25, electromagnetic waves that cannot be absorbed by the base sheet 12 can be reflected to the circuit board 4 side by the metal thin plate 26, and electromagnetic waves generated from the semiconductor elements 8 mounted on the circuit board 4 are reflected in the housing 2. Radiation from the operation opening 2b to the outside of the mobile phone 1 can be prevented.
Further, it is not necessary to attach an electromagnetic wave absorbing member in addition to the key sheet 25, and an electromagnetic wave countermeasure can be taken without increasing the bulk capacity of the mobile phone 1.

  Since the metal thin plate 26 is provided on the surface of the base sheet 12, the surface of the base sheet 12 can be reinforced.

Sixth Embodiment [FIGS. 12 and 13]:
A sectional view of the key sheet 27 of the sixth embodiment is shown in FIG. 12, and a plan view of the base sheet 28 is shown in FIG. The key sheet 27 of the sixth embodiment is different from the key sheet 25 of the fifth embodiment in that the base sheet 28 having the through holes 28e is provided and the radio wave reflection sheet 29 is provided.

  The base sheet 28 is formed of a rubber-like elastic body filled with a flat powdered electromagnetic wave absorber 13 as an “electromagnetic wave absorber”. Similarly to the base sheet 12 of the fifth embodiment, the base sheet 28 includes a pedestal portion 28a to which the resin key top 11 is fixed, a floating support portion 28b that supports the pedestal portion 28a so as to be capable of being pressed and displaced, and a metal dish for the circuit board 4. A pusher portion 28c that presses the spring 7 and a leg portion 28d that contacts the circuit board 4 are formed. The difference from the base sheet 12 is that a pedestal 28a is provided with a through hole 28e penetrating its thickness (FIG. 13).

  The radio wave reflection sheet 29 is an “electromagnetic wave reflection portion” that reflects radio waves, and is formed by providing the translucent resin film 29 a with the above-described translucent radio wave reflection layer 29 b made of the composite oxide conductor. Yes. The radio wave reflection sheet 29 is adhered and fixed so that the radio wave reflection layer 29 b side faces the base sheet 28 and follows the surface of the base sheet 28.

Next, a method for manufacturing the key sheet 27 will be described.
First, the electromagnetic wave absorber 13 is added and kneaded to an uncured rubber composition using a kneader to obtain a rubber composition in which the electromagnetic wave absorber 13 is uniformly dispersed. Next, a radio wave reflection sheet 29 is obtained by providing a light transmission layer 29b made of a composite oxide conductor by sputtering or vacuum deposition on the resin film 29a to obtain a radio wave reflection sheet 29, and then this radio wave reflection sheet using a jig or a mold. 29 is drawn into the same shape as the surface of the base sheet 28, and an adhesive is applied to the surface of the radio wave reflection layer 29b. The radio wave reflection sheet 29 is inserted into the molding die of the base sheet 28 so that the resin film 29a side is in contact with the molding die surface of the base sheet 28, and a rubber composition to which the electromagnetic wave absorbing material 13 is added is used as the base sheet 28. It is molded and cured with a molding die. In this way, the base sheet 28 in which the radio wave reflection sheet 29 is integrated and the electromagnetic wave absorber 13 is uniformly dispersed is obtained. Finally, the resin key top 11 which is separately injection-molded and provided with a printed layer representing the display element on the back surface is fixed to the radio wave reflection sheet 29 covering the pedestal portion 28a with an adhesive, whereby the key sheet 27 can be obtained.

According to the key sheet 27, the remaining electromagnetic wave that cannot be absorbed by the base sheet 28 can be reflected to the circuit board 4 side by the radio wave reflection sheet 29, and the electromagnetic wave generated from the semiconductor element 8 mounted on the circuit board 4 is Radiation from the operation opening 2b of the body 2 to the outside of the mobile phone 1 can be prevented.
Further, it is not necessary to attach an electromagnetic wave absorbing member in addition to the key sheet 27, and an electromagnetic wave countermeasure can be taken without increasing the bulk capacity of the mobile phone 1.

Since the base sheet 28 is provided with a through hole 28e that penetrates the thickness of the pedestal portion 28a, the through hole 28e can pass light from an illumination light source mounted on the circuit board. Therefore, the backlight light is transmitted to the radio wave reflection sheet 29 through the through hole 28e, can pass through the radio wave reflection sheet 29 and reach the resin key top 11, and the resin key top 11 can be illuminated by the backlight light. it can.
As described above, the radio wave that has passed through the hole of the through hole 28e from the circuit board 4 side is reflected by the radio wave reflection layer 29b, and the backlight light that has also passed through the hole of the through hole 28e passes through the radio wave reflection layer 29b. be able to. Therefore, radio waves generated on the circuit board 4 side are not emitted on the surface side of the key sheet 27, and the surface side of the key sheet 27 can be illuminated with backlight light.

  Since the radio wave reflection sheet 29 composed of the resin film 29a and the radio wave reflection layer 29b covers the surface of the base sheet 28, the surface of the base sheet 28 that has become brittle due to the filling of the electromagnetic wave absorber 13 can be protected. The surface of the sheet 28 can be made difficult to chip. Further, since the translucent resin film 29 a covers the surface side of the base sheet 28, the resin film 29 a can be used as the light guide layer of the base sheet 28.

Seventh Embodiment [FIG. 14]:
A cross-sectional view of the key sheet 30 of the seventh embodiment is shown in FIG. The key sheet 30 of the seventh embodiment is different from the key sheet 27 of the sixth embodiment in the configuration of the radio wave reflection sheet 31. The remaining configuration is the same as that of the key sheet 27.

  The radio wave reflection sheet 31 is an “electromagnetic wave reflection part” that reflects radio waves. Like the radio wave reflection sheet 29, the translucent resin film 31a is provided with a translucent radio wave reflection layer 31b made of a composite oxide conductor. Is formed. The radio wave reflection sheet 31 is adhered and fixed so that the radio wave reflection layer 31 b side faces the base sheet 28 and follows the surface of the base sheet 28. The difference from the radio wave reflection sheet 29 is that the surface of the base sheet 28 that covers the through-hole 28e is the uneven surface 31c that irregularly reflects radio waves.

Next, a method for manufacturing the key sheet 30 will be described.
First, the electromagnetic wave absorber 13 is added and kneaded to an uncured rubber composition using a kneader to obtain a rubber composition in which the electromagnetic wave absorber 13 is uniformly dispersed. Next, a radio wave reflecting sheet 31 is obtained by providing a translucent radio wave reflecting layer 31b made of a composite oxide conductor by sputtering or vacuum deposition on a resin film 31a having an uneven surface formed in a predetermined portion by embossing. . Thereafter, the radio wave reflection sheet 31 is drawn into the same shape as the surface of the base sheet 28 using a jig or a mold, and an adhesive is applied to the surface of the radio wave reflection layer 31b. The radio wave reflection sheet 31 is inserted into the molding die of the base sheet 28 so that the resin film 31a side is in contact with the molding die surface of the base sheet 28, and the rubber composition to which the electromagnetic wave absorbing material 13 is added is used as the base sheet 28. It is molded and cured with a molding die. In this way, the base sheet 28 in which the radio wave reflection sheet 31 is integrated and the electromagnetic wave absorbing material 13 is uniformly dispersed is obtained. Finally, the resin key top 11 which is separately injection-molded and provided with a printed layer representing a display element on the back surface is fixed to the radio wave reflection sheet 31 covering the pedestal portion 28a with an adhesive, whereby the key sheet 30 can be obtained.

According to the key sheet 30, the remaining electromagnetic waves that cannot be absorbed by the base sheet 28 can be reflected to the circuit board 4 side by the radio wave reflection sheet 31, and electromagnetic waves generated from the semiconductor elements 8 mounted on the circuit board 4 can be reflected. Radiation from the operation opening 2b of the body 2 to the outside of the mobile phone 1 can be prevented.
In addition, it is not necessary to attach an electromagnetic wave absorbing member in addition to the key sheet 30, and electromagnetic wave countermeasures can be taken without increasing the bulk capacity of the mobile phone 1.

  The radio wave that has passed through the through hole 28e from the circuit board 4 side is irregularly reflected by the uneven surface 31c of the radio wave reflecting layer 31b and propagates to the hole wall of the through hole 28e. That is, it is possible to make it difficult to regularly reflect the radio wave generated from the semiconductor element 8 mounted on the circuit board 4 toward the circuit board 4, and to reduce the radio wave transmitted to the semiconductor element 8. Similarly, the backlight light that has passed through the hole of the through hole 28e can pass through the radio wave reflection layer 31b. Therefore, radio waves generated on the circuit board 4 side are not emitted on the surface side of the key sheet 30, and the surface side of the key sheet 30 can be illuminated with backlight light.

  Since the radio wave reflection sheet 31 composed of the resin film 31a and the radio wave reflection layer 31b covers the surface of the base sheet 28, the surface of the base sheet 28 that has become brittle due to the filling of the electromagnetic wave absorber 13 can be protected. The surface of the sheet 28 can be made difficult to chip. Moreover, since the translucent resin film 31a covers the surface side of the base sheet 28, the resin film 31a can be used as the light guide layer of the base sheet 28. In this case, the light transmitted through the light guide layer is uneven. It is reflected toward the resin key top 11 by the surface 31c, and the resin key top 11 can be illuminated brightly.

Eighth Embodiment [FIGS. 15 and 16 (A)]:
A sectional view of the key sheet 32 of the eighth embodiment is shown in FIG. 15, and a perspective view of the pedestal portion 33a is shown in FIG. The key sheet 32 according to the eighth embodiment is different from the key sheet 27 according to the sixth embodiment in that the base sheet 33 includes a metal mesh 34 instead of the radio wave reflection sheet 29. The remaining configuration is the same as that of the key sheet 27.

  The base sheet 33 is formed of a rubber-like elastic body filled with a flat powdered electromagnetic wave absorber 13 as an “electromagnetic wave absorber”. Similarly to the base sheet 28 of the sixth embodiment, the base sheet 33 includes a pedestal portion 33a to which the resin key top 11 is fixed, a floating support portion 33b that supports the pedestal portion 33a so as to be capable of being pressed and displaced, and a metal dish for the circuit board 4. A pusher portion 33c that presses the spring 7, a leg portion 33d that contacts the circuit board 4, and a through hole 33e that penetrates the thickness of the pedestal portion 33a are formed. The difference from the base sheet 28 is that a recess 33f is provided for each through-hole 33e on the surface of the pedestal 33a (FIG. 16A).

  The metal mesh 34 reflects radio waves as an “electromagnetic wave reflection part”. It is attached to the concave portion 33f on the surface of the pedestal portion 33a and covers the surface side of the through hole 33e. Even with such a metal mesh, it is relatively weaker than a metal thin plate, but a high transmittance can be obtained while having a sufficient shielding effect. As for the wire diameter of the metal wire which comprises a mesh, 5 micrometers-100 micrometers are preferable. If it is less than 5 μm, the conductivity is insufficient and the shielding effect may be low. If it is larger than 100 μm, the transmitted light may be weakened. The distance between the metal wires is preferably 70 μm to 700 μm. If it is less than 70 μm, it is difficult for light to pass therethrough and the transmitted light may be weakened. If it is larger than 700 μm, the conductivity is insufficient and the shielding effect may be low.

Next, a method for manufacturing the key sheet 32 will be described.
First, the electromagnetic wave absorber 13 is added and kneaded to an uncured rubber composition using a kneader to obtain a rubber composition in which the electromagnetic wave absorber 13 is uniformly dispersed. Next, when this rubber composition is molded and cured with a molding die of the base sheet 33, the base sheet 33 in which the electromagnetic wave absorbing material 13 is uniformly dispersed is obtained. Thereafter, the metal mesh 34 is attached to the concave portion 33f provided on the surface of the pedestal portion 33a. Finally, the key sheet 32 can be obtained by fixing the resin key top 11 separately injection-molded and having a printed layer representing a display element on the back surface to the pedestal portion 33a with an adhesive.

According to the key sheet 32, the base sheet 33 absorbs electromagnetic waves generated from the semiconductor element 8 mounted on the circuit board 4, and the electromagnetic waves are radiated from the operation opening 2 b of the housing 2 to the outside of the mobile phone 1. Can be reduced. Furthermore, internal electromagnetic waves in the mobile phone 1 can also be reduced, and malfunction of other semiconductor elements 8 mounted on the circuit board 4 can be made difficult to occur. Therefore, it can be set as the mobile telephone 1 which improved the electromagnetic wave countermeasure.
In addition, it is not necessary to attach an electromagnetic wave absorbing member in addition to the key sheet 32, and an electromagnetic wave countermeasure can be taken without increasing the bulk capacity of the mobile phone 1.

  The radio wave that has passed through the through hole 33e from the circuit board 4 side is reflected by the metal mesh 34, and the backlight light that has also passed through the through hole 33e passes through the opening of the mesh of the metal mesh 34. Can do. Therefore, radio waves generated on the circuit board 4 side are not emitted on the front surface side of the key sheet 32, and the front surface side of the key sheet 32 can be illuminated with backlight light.

  In the key sheet 32 of the eighth embodiment, an example is shown in which the concave portion 33f is provided for each of the two through holes 33e formed in the pedestal portion 33a, and the metal mesh 34 is attached to each of the through holes 33e. As described above, two through holes 33e 'can be formed in one recess 33f' provided in the pedestal 33a ', and the two through holes 33e' can be covered with one metal mesh attached to the recess 33f '. .

Ninth Embodiment [FIG. 17]:
A key sheet 35 of the ninth embodiment is shown in FIG. The key sheet 35 of the ninth embodiment is different from the key sheet 27 of the sixth embodiment in that a radio wave reflector 36 is provided instead of the radio wave reflection sheet 29. The remaining configuration is the same as that of the key sheet 27.

  The radio wave reflector 36 reflects the radio wave as an “electromagnetic wave reflection part”, and is formed of a translucent resin filled with powder of a composite oxide conductor. It is embed | buried in the hole of the through-hole 28e in the base part 28a.

Next, a method for manufacturing the key sheet 35 will be described.
First, the electromagnetic wave absorber 13 is added and kneaded to an uncured rubber composition using a kneader to obtain a rubber composition in which the electromagnetic wave absorber 13 is uniformly dispersed. Next, when this rubber composition is molded and cured by a molding die of the base sheet 28, the base sheet 28 in which the electromagnetic wave absorbing material 13 is uniformly dispersed is obtained. Thereafter, a radio wave reflector 36 made of a translucent resin, which is filled with powder of a composite oxide conductor and separately molded, is fitted into the through hole 28e of the base sheet 28 and fixed with an adhesive or the like. Finally, the key sheet 35 can be obtained by fixing the resin key top 11 separately injection-molded and having a printed layer representing the display element on the back surface to the pedestal portion 28a with an adhesive.

According to the key sheet 35, the base sheet 28 absorbs electromagnetic waves generated from the semiconductor element 8 mounted on the circuit board 4, and the electromagnetic waves are radiated from the operation opening 2 b of the housing 2 to the outside of the mobile phone 1. Can be reduced. Furthermore, internal electromagnetic waves in the mobile phone 1 can also be reduced, and malfunction of other semiconductor elements 8 mounted on the circuit board 4 can be made difficult to occur. Therefore, it can be set as the mobile telephone 1 which improved the electromagnetic wave countermeasure.
In addition, it is not necessary to attach an electromagnetic wave absorbing member in addition to the key sheet 32, and an electromagnetic wave countermeasure can be taken without increasing the bulk capacity of the mobile phone 1.

  The electromagnetic wave generated from the semiconductor element 8 mounted on the circuit board 4 is reflected by the radio wave reflector 36 embedded in the through hole 28e and cannot pass through the through hole 28e, and the backlight light is transmitted through the through hole 28e. The electromagnetic wave reflector 36 embedded in the hole can be transmitted. Therefore, radio waves generated on the circuit board 4 side are not radiated on the surface side of the key sheet 35, and the surface side of the key sheet 35 can be illuminated with the backlight.

  In the key sheet 35 of the ninth embodiment, an example is shown in which the radio wave reflector 36 completely fills the hole of the through hole 28e and the front and back surfaces of the pedestal portion 28a and the front and back surfaces of the radio wave reflector 36 are flush with each other. However, the back surface of the radio wave reflector 36 may be recessed from the back surface of the pedestal portion 28a. Further, the back surface of the radio wave reflector 36 can be an uneven surface.

Tenth Embodiment [FIG. 18]:
A key sheet 37 of the tenth embodiment is shown in FIG. The key sheet 37 of the tenth embodiment is different from the key sheet 27 of the sixth embodiment in that the radio wave reflection sheet 29 is removed and a radio wave reflection layer 38 is provided. The remaining configuration is the same as that of the key sheet 27.

  The radio wave reflection layer 38 is an “electromagnetic wave reflection portion” that reflects radio waves, and is formed of a translucent resin filled with powder of a composite oxide conductor. The back surface of the resin key top 11 is applied.

Next, a method for manufacturing the key sheet 37 will be described.
First, the electromagnetic wave absorber 13 is added and kneaded to an uncured rubber composition using a kneader to obtain a rubber composition in which the electromagnetic wave absorber 13 is uniformly dispersed. Next, when this rubber composition is molded and cured by a molding die of the base sheet 28, the base sheet 28 in which the electromagnetic wave absorbing material 13 is uniformly dispersed is obtained. Finally, the resin key top 11 is separately mounted by injection molding, which is separately injection-molded and sequentially provided with a printed layer representing a display element on the back surface and a radio wave reflecting layer 38 made of a translucent resin filled with powder of a composite oxide conductor. The key sheet 37 can be obtained by being fixed to the portion 28a.

According to the key sheet 37, the remaining electromagnetic waves that cannot be absorbed by the base sheet 28 can be reflected to the circuit board 4 side by the radio wave reflection layer 38, and the electromagnetic waves generated from the semiconductor element 8 mounted on the circuit board 4 are Radiation from the operation opening 2b of the body 2 to the outside of the mobile phone 1 can be prevented.
In addition, it is not necessary to attach an electromagnetic wave absorbing member in addition to the key sheet 37, and an electromagnetic wave countermeasure can be taken without increasing the bulk capacity of the mobile phone 1.

Since the base sheet 28 is provided with a through hole 28e that penetrates the thickness of the pedestal portion 28a, the through hole 28e can pass light from an illumination light source mounted on the circuit board. Therefore, the backlight light is transmitted to the radio wave reflection layer 38 through the through hole 28e, can pass through the radio wave reflection layer 38 and reach the resin key top 11, and the resin key top 11 can be illuminated by the backlight light. it can.
As described above, the radio wave that has passed through the through hole 28e from the circuit board 4 side is reflected by the radio wave reflecting layer 38, and the backlight light that has also passed through the through hole 28e passes through the radio wave reflecting layer 38. be able to. Therefore, radio waves generated on the circuit board 4 side are not emitted on the surface side of the key sheet 37, and the surface side of the key sheet 27 can be illuminated with backlight light.

Eleventh Embodiment (FIG. 19):
A key sheet 39 of the eleventh embodiment is shown in FIG. The key sheet 39 according to the eleventh embodiment is different from the key sheet 10 according to the second embodiment in that the structure of the base sheet 40 and the electromagnetic wave absorbing print layer 41 are provided. The remaining configuration is the same as that of the key sheet 10.

  The base sheet 40 is formed of a rubber-like elastic body that does not contain an electromagnetic wave absorber. On the surface of the base sheet 40, the resin key top 11 is fixed to a flat pedestal portion 40a with an adhesive not shown. A floating support portion 40b is provided around the pedestal portion 40a to support the pedestal portion 40a so as to be capable of being pressed and displaced. On the back surface of the base sheet 40, a cylindrical pusher portion 40c that presses the metal disc spring 7 of the circuit board 4 is formed for each pedestal portion 40a, and the leg portion between the entire outer periphery and adjacent pedestal portions 40a. The front end of the leg portion 40 d is in contact with the surface of the circuit board 4.

  The electromagnetic wave absorbing printing layer 41 is a coating layer made of a polymer composition containing the flat electromagnetic wave absorbing material 13 as an “electromagnetic wave absorbing portion”, and is applied to the surface of the flat base sheet 40. The flat electromagnetic wave absorbing material 13 contained in the electromagnetic wave absorbing printing layer 41 is oriented along the surface direction of the base sheet 40.

Next, a method for manufacturing the key sheet 39 will be described.
First, a rubber composition not containing an electromagnetic wave absorbing material is molded and cured with a molding die for the base sheet 40 to obtain the base sheet 40. Next, the electromagnetic wave absorbing material 9 is added and kneaded to the uncured liquid rubber composition using a kneader to obtain an ink in which the electromagnetic wave absorbing material 9 is uniformly dispersed. This ink is screen printed on the surface of the base sheet 40 to obtain the base sheet 40 having the electromagnetic wave absorbing print layer 41 on the surface. Finally, the key sheet 39 can be obtained by fixing the resin key top 11 separately molded by injection molding and having the printed layer representing the display element on the back surface to the electromagnetic wave absorbing printed layer 41 covering the pedestal portion 40a with an adhesive.

According to the key sheet 39, since the electromagnetic wave absorbing print layer 41 is provided on the surface of the base sheet 40, the electromagnetic wave absorbing print layer 41 absorbs electromagnetic waves generated from the semiconductor element 8 mounted on the circuit board 4, and the housing 2 It is possible to reduce the emission of electromagnetic waves from the operation opening 2b to the outside of the mobile phone 1. Furthermore, internal electromagnetic waves in the mobile phone 1 can also be reduced, and malfunction of other semiconductor elements 8 mounted on the circuit board 4 can be made difficult to occur. From the above, the mobile phone 1 with improved electromagnetic wave countermeasures can be obtained.
The electromagnetic wave absorbing printing layer 41 can have a higher degree of orientation than the radio wave absorbing portion formed by the molded body because the flat electromagnetic wave absorbing material 13 is oriented along the surface of the base sheet 40 in the process of solvent evaporation after application. For this reason, even if the electromagnetic wave absorption printing layer 41 is a thin layer, sufficient electromagnetic wave absorption performance can be exhibited, and the thin key sheet 39 can be realized.
Moreover, since the mixture of the electromagnetic wave absorbing material 13 and the resin used for printing contains a solvent and is adjusted to a viscosity suitable for relatively low viscosity printing, the electromagnetic wave absorbing material 13 is strong against the electromagnetic wave absorbing material 13 when mixed into the resin. Hard to apply force. Therefore, the electromagnetic wave absorbing material 13 can be prevented from being broken and broken, and the high aspect ratio electromagnetic wave absorbing material 13 having relatively low strength can be used.

Modified example of the eleventh embodiment (FIG. 20):
A sectional view of a key sheet 42 which is a modification of the eleventh embodiment is shown in FIG. In the key sheet 39, the example in which the electromagnetic wave absorbing print layer 41 is provided on the surface of the base sheet 40 has been shown, but in the key sheet 42, the low refractive layer 43 and the light guide plate 44 are sequentially provided on the surface of the electromagnetic wave absorbing print layer 41, A diffusion layer 45 is provided on the back surface of the resin key top 11.
By providing the low refraction layer 43, the light incident from the side surface can be totally reflected at the interface between the light guide plate 44 and the low refraction layer 43, and the light can be guided to a place away from the light source. For example, if a light source is provided on the side surface of the base sheet 40, light can be guided to the surface side of the base sheet 40 by the light guide plate 44, and the resin key top 11 can be illuminated by the diffusion layer 45. The key sheet 42 is obtained.

  For the light guide plate 44, a general transparent resin such as polycarbonate resin, acrylic resin, silicone, urethane, or the like can be used. The low refractive layer 43 uses a resin having a relatively low refractive index as compared with the light guide plate 44. This is because when the refractive index is the same or high, total reflection does not occur and bright illumination cannot be performed. As the low refraction layer 43, for example, a silicone-based adhesive material may be used to fix the light guide plate 44 and the electromagnetic wave absorbing member.

The refractive index difference between the low refractive layer 43 and the light guide plate 44 is preferably 0.1 or more, and more preferably 0.2 or more. For example, when the low refractive layer 43 with a refractive index of 1.49 is provided on the light guide plate 44 with a refractive index of 1.59, the total reflection angle is about 22 °. Further, when the low refractive layer 43 having a refractive index of 1.40 is provided on the light guide plate 44 having a refractive index of 1.59, the total reflection angle is about 31 °, and a distant place can be illuminated brightly. The refractive index of polycarbonate resin is about 1.59, the refractive index of acrylic resin is about 1.49, and the refractive index of dimethyl silicone is about 1.40.
The resin used for the light guide plate 44 is determined by the relationship with the resin that can be used for the low refractive layer 44. However, if the refractive index is too high, the light reflection coefficient at the interface between the air and the resin increases, which is efficient. If light cannot be taken into the light guide plate 44 and the refractive index is too low, the resin that can be used for the low refractive layer 43 is limited. Therefore, the refractive index of 1.45 or more and 1.9 or less is appropriate as the resin used for the light guide plate 44.

  The forms of the electromagnetic wave absorber and the electromagnetic wave reflector shown in the above embodiments can be used in appropriate combination. For example, in the fifth embodiment (FIG. 5), the entire base sheet 12 is an electromagnetic wave absorbing portion including an electromagnetic wave absorbing material, and a metal thin plate 26 is provided on the surface thereof. The base sheet 22 includes an electromagnetic wave absorbing material in the floating support portion 22b and the leg portion 22d used in the third embodiment (FIG. 7), and the structure is changed to a film containing a composite oxide conductor instead of the thin metal plate 26. Etc.

The external view which shows a mobile telephone provided with the key sheet of 1st Embodiment. The principal part enlarged view of the SA-SA line cross section of FIG. Sectional drawing which shows the key sheet of 2nd Embodiment. Sectional drawing which shows the 1st modification in the key sheet of 2nd Embodiment. Sectional drawing which shows the 2nd modification in the key sheet of 2nd Embodiment. Sectional drawing which shows the 3rd modification in the key sheet of 2nd Embodiment. Sectional drawing which shows the key sheet of 3rd Embodiment. The exploded plan view showing the key sheet of a 3rd embodiment. Sectional drawing which shows the key sheet of 4th Embodiment. The disassembled plan view which shows the key sheet of 4th Embodiment. Sectional drawing which shows the key sheet of 5th Embodiment. Sectional drawing which shows the key sheet of 6th Embodiment. The top view which shows the base sheet used for the key sheet of 6th Embodiment. Sectional drawing which shows the key sheet of 7th Embodiment. Sectional drawing which shows the key sheet of 8th Embodiment. It is expansion explanatory drawing of a base part, A part view (A) is a perspective view which shows the base part in the key sheet of 8th Embodiment, A part view (B) is the modification of the base part in the key sheet of 8th Embodiment. FIG. Sectional drawing which shows the key sheet of 9th Embodiment. Sectional drawing which shows the key sheet of 10th Embodiment. Sectional drawing which shows the key sheet | seat of 11th Embodiment. Sectional drawing which shows the modification in the key sheet of 11th Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cellular phone 2 Case 2a Holding part 2b Operation opening 2c Partition rail 3 Key sheet (1st Embodiment)
4 Circuit board 5 Key top part (electromagnetic wave absorption part)
6 Base sheet (electromagnetic wave absorber)
6a Floating support part 6b Pusher part 6c Leg part 7 Metal disc spring (contact switch)
8 Semiconductor Element 9 Electromagnetic Wave Absorbing Material 10 Key Sheet (Second Embodiment)
11 Resin key top 12 Base sheet (electromagnetic wave absorber)
12a Pedestal part 12b Floating support part 12c Pusher part 12d Leg part 13 Electromagnetic wave absorber 14 Key sheet (first modification of the second embodiment)
15 Polymer coating layer 16 Key sheet (second modification of the second embodiment)
17 Polymer coating layer 18 Key sheet (third modification of the second embodiment)
19 Polymer coating layer 20 Polymer coating layer 21 Key sheet (third embodiment)
22 Base sheet 22a Pedestal part 22b Floating support part (electromagnetic wave absorption part)
22c Pusher part 22d Leg part (electromagnetic wave absorption part)
23 Key sheet (fourth embodiment)
24 base sheet 24a pedestal 24b floating support 24c pusher 24d leg (electromagnetic wave absorber)
25 Key sheet (fifth embodiment)
26 Metal thin plate (electromagnetic wave reflection part)
27 Key sheet (sixth embodiment)
28 Base sheet (electromagnetic wave absorber)
28a Pedestal part 28b Floating support part 28c Pusher part 28d Leg part 28e Through hole 29 Radio wave reflection sheet (electromagnetic wave reflection part)
29a Resin film 29b Radio wave reflection layer 30 Key sheet (seventh embodiment)
31 Radio wave reflection sheet (electromagnetic wave reflection part)
31a Resin film 31b Radio wave reflection layer 31c Uneven surface 32 Key sheet (8th Embodiment)
33 Base sheet (electromagnetic wave absorber)
33a, 33a ′ pedestal portion 33b, 33b ′ floating support portion 33c pusher portion 33d leg portion 33e, 33e ′ through hole 33f, 33f ′ concave portion 34 metal mesh (electromagnetic wave reflection portion)
35 Key sheet (9th embodiment)
36 Radio wave reflector (electromagnetic wave reflector)
37 Key sheet (10th embodiment)
38 Radio wave reflection layer (electromagnetic wave reflection part)
39 Key sheet (11th embodiment)
40 Base sheet 40a Pedestal part 40b Floating support part 40c Pusher part 40d Leg part 41 Electromagnetic wave absorption printing layer (electromagnetic wave absorption part)
42 Key sheet (modified example of the eleventh embodiment)
43 Low refractive layer 44 Light guide plate 45 Diffusion layer

Claims (17)

In a key sheet having a base sheet that floats and supports the pressing operation unit and is placed on the circuit board,
A key sheet comprising an electromagnetic wave absorbing portion containing an electromagnetic wave absorbing material in a base sheet. The pressing operation part is a resin key top,
The base sheet has a translucent pedestal portion that fixes the resin key top, a floating support portion that supports the pedestal portion so that it can be pressed and displaced, and a leg portion that supports the floating support portion on the circuit board. Made of rubber-like elastic body,
The key sheet according to claim 1, wherein an electromagnetic wave absorbing portion is provided on the leg portion. The pressing operation part is a resin key top,
The base sheet has a translucent pedestal portion that fixes the resin key top, a floating support portion that supports the pedestal portion so that it can be pressed and displaced, and a leg portion that supports the floating support portion on the circuit board. Made of rubber-like elastic body,
The key sheet according to claim 1, wherein an electromagnetic wave absorbing portion is provided on the floating support portion.   The key sheet according to any one of claims 1 to 3, wherein the base sheet is formed of a rubber-like elastic body, and an electromagnetic wave absorbing portion is provided on the entire base sheet. The pressing operation part is a resin key top,
The base sheet is a rubber-like elastic body provided with a coating layer on its surface,
The key sheet according to claim 1, wherein an electromagnetic wave absorbing portion is provided in the coating layer.   The key sheet according to claim 1, wherein a layered electromagnetic wave reflecting portion is provided on the surface side of the base sheet.   The key sheet according to claim 6, wherein the electromagnetic wave reflecting portion is a thin metal plate.   The key sheet according to claim 6, wherein the electromagnetic wave reflection portion is a metal mesh.   The key sheet according to claim 6, wherein the electromagnetic wave reflection part includes a complex oxide conductor and is translucent.   The key sheet according to any one of claims 6 to 9, wherein a surface of the electromagnetic wave reflecting portion facing the circuit board is an uneven surface.   The base sheet is provided with a through hole through which light from an illumination light source mounted on a circuit board is passed, and an electromagnetic wave reflecting portion filled with a translucent resin containing a composite oxide conductor is provided in the through hole. The key sheet according to any one of 10.   The key sheet according to any one of claims 1 to 11, wherein the base sheet is provided with a through hole through which light from an illumination light source mounted on a circuit board is passed, and a metal mesh that closes the through hole is provided.   The key sheet according to any one of claims 1 to 12, wherein a polymer coating layer is further provided on at least either the front surface side or the back surface side of the base sheet.   The key sheet according to claim 1, wherein a light guide plate is provided on the outermost surface of the base sheet.   The key sheet according to claim 14, wherein a low refractive layer is provided between the base sheet and the light guide plate.   The key sheet according to any one of claims 1 to 15, wherein the electromagnetic wave absorbing material is a flat powder and has an electromagnetic wave absorbing portion in which the flat powder is oriented along the surface direction of the base sheet.   The key sheet according to any one of claims 1 to 16, wherein the electromagnetic wave absorbing material is a soft magnetic powder.

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