Multilayer sheet, multilayer substrate, electronic apparatus, soundboard, and musical instrument

Abstract

In this multilayer sheet including a liquid crystal polymer sheet, mechanical strength is improved and desired physical characteristics are achieved. A multilayer sheet (11) includes a first liquid crystal polymer sheet (12a), a second liquid crystal polymer sheet (13a), and a third liquid crystal polymer sheet (12b). The second liquid crystal polymer sheet (13a) includes a liquid crystal polymer as a material and is aligned in a first direction (D11) orthogonal to the thickness direction of the multilayer sheet (11). Each of the first liquid crystal polymer sheet (12a) and the third liquid crystal polymer sheet (12b) includes a liquid crystal polymer as a material, and has a degree of alignment lower than that of the second liquid crystal polymer sheet (13a). In the thickness direction of the multilayer sheet (11), the second liquid crystal polymer sheet (13a) is sandwiched between and in contact with the first liquid crystal polymer sheet (12a) and the third liquid crystal polymer sheet (12b).

Description

Multilayer Sheet, Multilayer Substrate, Electronic Device, Soundboard, and Musical Instrument

[0001] The present invention generally relates to a multilayer sheet, a multilayer substrate, an electronic device, a soundboard, and a musical instrument, and more particularly to a multilayer sheet including a liquid crystal polymer sheet, and a multilayer substrate, an electronic device, a soundboard, and a musical instrument including the multilayer sheet.

[0002] Patent Document 1 discloses an electronic circuit board having a liquid crystal polymer sheet.

[0003] Japanese Patent Application Laid-Open No. 2007-19338

[0004] In a liquid crystal polymer sheet, when the degree of orientation of the liquid crystal polymer is low, the anisotropy of physical properties such as the dielectric constant and Young's modulus of the multilayer substrate is low, so it is difficult to make the physical properties of the multilayer substrate the desired properties. On the other hand, in a liquid crystal polymer sheet, when the degree of orientation of the liquid crystal polymer is high, the tensile strength and peel strength are low in a specific direction, so sufficient mechanical strength may not be obtained.

[0005] An object of the present invention is to improve the mechanical strength and obtain desired physical properties in a multilayer sheet, a multilayer substrate, an electronic device, a soundboard, and a musical instrument including a liquid crystal polymer sheet.

[0006] The multilayer sheet according to one aspect of the present invention includes a first liquid crystal polymer sheet, a second liquid crystal polymer sheet, and a third liquid crystal polymer sheet. The second liquid crystal polymer sheet contains a liquid crystal polymer as a material and is oriented in a first direction orthogonal to the thickness direction of the multilayer sheet. Each of the first liquid crystal polymer sheet and the third liquid crystal polymer sheet contains a liquid crystal polymer as a material and has a lower degree of orientation than the second liquid crystal polymer sheet. In the thickness direction of the multilayer sheet, the second liquid crystal polymer sheet is sandwiched between and in contact with the first liquid crystal polymer sheet and the third liquid crystal polymer sheet.

[0007] The multilayer substrate according to one aspect of the present invention includes the multilayer sheet and a conductor layer disposed on a main surface of the multilayer sheet.

[0008] The multilayer substrate according to one aspect of the present invention includes the multilayer sheet and a signal line disposed on or inside a main surface of the multilayer sheet.

[0009] An electronic device according to one aspect of the present invention comprises the multilayer substrate and a signal processing circuit connected to the signal line.

[0010] A soundboard according to one aspect of the present invention comprises a support plate and the multilayer sheet. The multilayer sheet is arranged on the support plate.

[0011] An instrument according to one aspect of the present invention comprises a soundboard and a sound source. Sound emitted from the sound source propagates in the first direction.

[0012] In the multilayer sheets, multilayer substrates, electronic devices, soundboards, and musical instruments according to the above embodiment, it is possible to improve mechanical strength and obtain desired physical properties.

[0013] Figure 1 is a cross-sectional view taken along line I-I in Figure 2, relating to a multilayer substrate according to Embodiment 1. Figure 2 is a plan view showing the main part of the multilayer substrate. Figure 3 is a schematic diagram showing the orientation axis of the second liquid crystal polymer sheet with respect to the multilayer substrate. Figure 4 is a cross-sectional view of the main part of an electronic device equipped with the multilayer substrate. Figure 5 is a schematic diagram showing the orientation axis of the second liquid crystal polymer sheet with respect to a multilayer substrate according to Embodiment 2. Figure 6 is a cross-sectional view taken along line VI-VI in Figure 7, relating to a multilayer substrate according to Embodiment 3. Figure 7 is a plan view showing the main part of the multilayer substrate. Figure 8 is a schematic diagram showing the orientation axis of the second liquid crystal polymer sheet with respect to the multilayer substrate. Figure 9 is a schematic diagram of a multilayer substrate according to Embodiment 4. Figure 10 is a schematic diagram of a multilayer substrate according to a modified example of Embodiment 4. Figure 11 is a schematic diagram of a musical instrument according to Embodiment 5. Figure 12 is an exploded view of the soundboard of the musical instrument.

[0014] Embodiments 1 to 5 will be described below with reference to the drawings. The drawings referenced in Embodiments 1 to 5 below are schematic diagrams, and the size and thickness of the components shown in the drawings do not necessarily reflect the actual dimensions, nor do the ratios of size and thickness between components necessarily reflect the actual dimensional ratios. Furthermore, each drawing defines and represents a Cartesian coordinate system with three mutually orthogonal axes: the X, Y, and Z axes. The X, Y, and Z axes are all virtual axes, and the arrows indicating "X," "Y," and "Z" in the drawings are for illustrative purposes only and do not represent actual objects.

[0015] (Embodiment 1) The multilayer sheet 11, multilayer substrate 1, and electronic device 500 according to Embodiment 1 will be described with reference to Figures 1 to 4.

[0016] (1) Multilayer substrate embodiment 1, as shown in Figures 1 and 2, comprises a multilayer sheet 11, a signal line 2, a first ground electrode 31, a second ground electrode 32, a third ground electrode 33, and a fourth ground electrode 34.

[0017] The multilayer substrate 1 is housed in the casing 501 of the electronic device 500, for example, as shown in Figure 4. The electronic device 500 is, for example, a communication device. The communication device is, for example, a mobile phone (e.g., a smartphone), but is not limited to a mobile phone; it may also be, for example, a notebook personal computer, a wearable device (e.g., a smartwatch), etc.

[0018] Hereinafter, each component of the multilayer substrate 1 according to this embodiment will be described with reference to the drawings.

[0019] (1.1) Multilayer Sheet In this embodiment, as shown in Figure 2, the multilayer sheet 11 is elongated along the Y-axis direction which is perpendicular to the Z-axis direction, which is the thickness direction of the multilayer sheet 11.

[0020] The multilayer sheet 11 has a first main surface 14 and a second main surface 15.

[0021] As shown in Figure 1, the multilayer sheet 11 has multiple (three in the illustrated example) sheets 11a, 11b, and 11c, and the multiple sheets 11a, 11b, and 11c are stacked together. The thickness direction of the multilayer sheet 11 is the stacking direction of the multiple sheets 11a, 11b, and 11c.

[0022] The thickness of the multilayer sheet 11 is, for example, 10 μm or more and 120 μm or less.

[0023] Sheet 11a has a first main surface 111a and a second main surface 112a. The first main surface 111a is included in the first main surface 14 of the multilayer sheet 11. The second main surface 112a is in contact with sheet 11b.

[0024] Sheet 11a includes a first liquid crystal polymer sheet 12a, a second liquid crystal polymer sheet 13a, and a third liquid crystal polymer sheet 12b. The thicknesses of the first liquid crystal polymer sheet 12a and the third liquid crystal polymer sheet 12b are, for example, equal to each other. However, the thicknesses of the first liquid crystal polymer sheet 12a and the third liquid crystal polymer sheet 12b may be different. The thickness of the second liquid crystal polymer sheet 13a is, for example, twice the thickness of the first liquid crystal polymer sheet 12a and the third liquid crystal polymer sheet 12b, respectively.

[0025] Sheet 11b has a first main surface 111b and a second main surface 112b. The first main surface 111b is in contact with the second main surface 112a of sheet 11a. The second main surface 112b is in contact with sheet 11c.

[0026] The sheet 11b also includes a first liquid crystal polymer sheet 12c, a second liquid crystal polymer sheet 13b, and a third liquid crystal polymer sheet 12d. The thicknesses of the first liquid crystal polymer sheet 12c and the third liquid crystal polymer sheet 12d are, for example, equal to each other. The thickness of the second liquid crystal polymer sheet 13b is, for example, twice the thickness of the first liquid crystal polymer sheet 12c and the third liquid crystal polymer sheet 12d, respectively.

[0027] Sheet 11c has a first main surface 111c and a second main surface 112c. The first main surface 111c is in contact with the second main surface 112b of sheet 11b. The second main surface 112b is included in the second main surface 15 of the multilayer sheet 11.

[0028] Sheet 11c includes a first liquid crystal polymer sheet 12e, a second liquid crystal polymer sheet 13c, and a third liquid crystal polymer sheet 12f. The thicknesses of the first liquid crystal polymer sheet 12e and the third liquid crystal polymer sheet 12f are, for example, equal to each other. The thickness of the second liquid crystal polymer sheet 13c is, for example, twice the thickness of the first liquid crystal polymer sheet 12e and the third liquid crystal polymer sheet 12f, respectively.

[0029] In other words, the multilayer sheet 11 includes first liquid crystal polymer sheets 12a, 12c, and 12e, second liquid crystal polymer sheets 13a, 13b, and 13c, and third liquid crystal polymer sheets 12b, 12d, and 12f.

[0030] The material of the multiple first liquid crystal polymer sheets 12a, 12c, 12e and the multiple third liquid crystal polymer sheets 12b, 12d, 12f (hereinafter, when the six liquid crystal polymer sheets 12a, 12b, 12c, 12d, 12d, and 12f are not distinguished from each other, each will be referred to as "liquid crystal polymer sheet 12") includes a liquid crystal polymer. The liquid crystal polymer is, for example, a thermoplastic liquid crystal polymer.

[0031] The material of the multiple second liquid crystal polymer sheets 13a, 13b, and 13c (hereinafter, unless otherwise distinguished, each will be referred to as "liquid crystal polymer sheet 13") includes a liquid crystal polymer. The liquid crystal polymer is, for example, a thermoplastic liquid crystal polymer.

[0032] It is preferable that the first liquid crystal polymer sheet 12a, the second liquid crystal polymer sheet 13a, and the third liquid crystal polymer sheet 12b are made of the same material. This makes it less likely for the first liquid crystal polymer sheet 12a and the third liquid crystal polymer sheet 12b to peel off from the second liquid crystal polymer sheet 13a in sheet 11a.

[0033] It is preferable that the first liquid crystal polymer sheet 12c, the second liquid crystal polymer sheet 13b, and the third liquid crystal polymer sheet 12d are made of the same material. This makes it less likely for the first liquid crystal polymer sheet 12c and the third liquid crystal polymer sheet 12d to peel off from the second liquid crystal polymer sheet 13b in sheet 11b.

[0034] It is preferable that the first liquid crystal polymer sheet 12e, the second liquid crystal polymer sheet 13c, and the third liquid crystal polymer sheet 12f are made of the same material. This makes it less likely for the first liquid crystal polymer sheet 12e and the third liquid crystal polymer sheet 12f to peel off from the second liquid crystal polymer sheet 13c in sheet 11c.

[0035] The first liquid crystal polymer sheet 12a, the second liquid crystal polymer sheet 13a, and the third liquid crystal polymer sheet 12b are in close contact with each other in the Z-axis direction, for example, by thermocompression bonding. In other words, no adhesive layer or the like is provided between the first liquid crystal polymer sheet 12a and the second liquid crystal polymer sheet 13a, and between the second liquid crystal polymer sheet 13a and the third liquid crystal polymer sheet 12b.

[0036] The first liquid crystal polymer sheet 12c, the second liquid crystal polymer sheet 13b, and the third liquid crystal polymer sheet 12d are in close contact with each other in the Z-axis direction, for example, by thermocompression bonding. In other words, no adhesive layer or the like is provided between the first liquid crystal polymer sheet 12c and the second liquid crystal polymer sheet 13b, and between the second liquid crystal polymer sheet 13b and the third liquid crystal polymer sheet 12d.

[0037] The first liquid crystal polymer sheet 12e, the second liquid crystal polymer sheet 13c, and the third liquid crystal polymer sheet 12f are in close contact with each other in the Z-axis direction, for example, by thermocompression bonding. In other words, no adhesive layer or the like is provided between the first liquid crystal polymer sheet 12e and the second liquid crystal polymer sheet 13c, and between the second liquid crystal polymer sheet 13c and the third liquid crystal polymer sheet 12f.

[0038] Each of the multiple liquid crystal polymer sheets 13 is oriented in a first direction perpendicular to the thickness direction of the multilayer sheet 11. Here, "the liquid crystal polymer is oriented in the first direction" means that the longitudinal directions of the multiple rod-shaped molecules constituting the liquid crystal polymer are parallel to the first direction. "The longitudinal directions of the rod-shaped molecules are parallel to the first direction" includes not only cases where the longitudinal directions of the rod-shaped molecules and the first direction are strictly parallel, but also cases where the angle between the longitudinal direction of the rod-shaped molecules and the first direction is 45 degrees or less for 50% or more of the rod-shaped molecules.

[0039] As shown in Figure 3, in the second liquid crystal polymer sheet 13a, the liquid crystal polymer is oriented in the first direction, direction D11. Direction D11 is along the Y-axis. In the second liquid crystal polymer sheet 13b, the liquid crystal polymer is oriented in the first direction, direction D21. Direction D21 is along the Y-axis. In the second liquid crystal polymer sheet 13c, the liquid crystal polymer is oriented in the first direction, direction D31. Direction D31 is along the Y-axis.

[0040] In each of the multiple liquid crystal polymer sheets 12, the degree of orientation of the liquid crystal polymer is lower than the degree of orientation of the liquid crystal polymer in the multiple liquid crystal polymer sheets 13. "Degree of orientation of liquid crystal polymer" refers to the degree to which the longitudinal directions of the multiple rod-shaped molecules constituting the liquid crystal polymer are aligned. The degree of orientation of the liquid crystal polymer can be measured, for example, by analyzing the measurement results of X-ray diffraction. Specifically, the diffraction spectrum of liquid crystal polymer sheet 12 has more peaks than the diffraction spectrum of liquid crystal polymer sheet 13. In each of the multiple liquid crystal polymer sheets 12, it is preferable that the orientations of the multiple rod-shaped molecules are misaligned.

[0041] The second liquid crystal polymer sheet 13a is sandwiched between the first liquid crystal polymer sheet 12a and the third liquid crystal polymer sheet 12b, in contact with each other. The second liquid crystal polymer sheet 13b is sandwiched between the first liquid crystal polymer sheet 12c and the third liquid crystal polymer sheet 12d, in contact with each other. The second liquid crystal polymer sheet 13c is sandwiched between the first liquid crystal polymer sheet 12e and the third liquid crystal polymer sheet 12f, in contact with each other.

[0042] (1.2) Signal Line, Third Ground Electrode, and Fourth Ground Electrode As shown in FIGS. 1 and 2, the signal line 2 is disposed within the multilayer sheet 11. Also, the third ground electrode 33 and the fourth ground electrode 34 are disposed within the multilayer sheet 11. More specifically, the signal line 2, the third ground electrode 33, and the fourth ground electrode 34 are disposed on the first main surface 111b of the sheet 11b and are in contact with the second main surface 112a of the sheet 11a, as shown in FIG. 1. The signal line 2 is, for example, a signal line through which a high-frequency signal is transmitted. The frequency of the high-frequency signal is, for example, 1 GHz or higher, but is not limited to 1 GHz or higher and may be less than 1 GHz. The multilayer substrate 1 of the present embodiment is designed such that the impedance of the signal line 2 is 50 Ω.

[0043] The signal line 2 is disposed sandwiched between the first ground electrode 31 and the second ground electrode 32 in the Z-axis direction. In the present embodiment, a strip line is formed by the multilayer sheet 11, the signal line 2, the first ground electrode 31, and the second ground electrode. Also, the signal line 2 is disposed sandwiched between the third ground electrode 33 and the fourth ground electrode 34 in the X-axis direction.

[0044] Each of the signal line 2, the third ground electrode 33, and the fourth ground electrode 34 has conductivity. The material of the signal line 2 includes, for example, copper. Each of the signal line 2, the third ground electrode 33, and the fourth ground electrode 34 is formed in a predetermined pattern. The thickness of each of the signal line 2, the third ground electrode 33, and the fourth ground electrode 34 is, for example, 3 μm or more and 40 μm or less. Each of the signal line 2, the third ground electrode 33, and the fourth ground electrode 34 is formed, for example, by patterning a first copper foil attached to the multilayer sheet that is the base of the sheet 11b.

[0045] In a plan view of the multilayer sheet 11 from the thickness direction, the signal line 2, the third ground electrode 33, and the fourth ground electrode 34 are all straight. The signal line 2 has a length in the direction along the Y axis that is longer than its length in the direction along the X axis. In a plan view of the multilayer sheet 11 from the thickness direction, the signal line 2, the third ground electrode 33, and the fourth ground electrode 34 may have shapes other than straight lines, for example, they may be curved or bent.

[0046] The third ground electrode 33 has a length in the direction along the Y axis that is longer than its length in the direction along the X axis. The third ground electrode 33 is perpendicular to the thickness direction of the multilayer sheet 11 and is spaced away from the signal line 2 in the X axis direction that is perpendicular to the longitudinal direction of the signal line 2. The fourth ground electrode 34 has a length in the direction along the Y axis that is longer than its length in the direction along the X axis. The fourth ground electrode 34 is perpendicular to the thickness direction of the multilayer sheet 11 and is spaced away from the signal line 2 in the X axis direction that is perpendicular to the longitudinal direction of the signal line 2. The signal line 2 is located between the third ground electrode 33 and the fourth ground electrode 34 in the X axis direction that is perpendicular to the thickness direction of the multilayer sheet 11 and is perpendicular to the longitudinal direction of the signal line 2.

[0047] (1.3) First ground electrode The first ground electrode 31 is located on the first main surface 14 of the multilayer sheet 11. The first ground electrode 31 corresponds to the conductor layer of this disclosure. The first ground electrode 31 is in contact with the first main surface 14 of the multilayer sheet 11. In the thickness direction of the multilayer sheet 11, the first ground electrode 31 faces the signal line 2 and the second ground electrode 32.

[0048] The first ground electrode 31 has conductivity. The material of the first ground electrode 31 is, for example, copper. The thickness of the first ground electrode 31 is, for example, 3 μm or more and 40 μm or less. The first ground electrode 31 is formed in a predetermined pattern. In a plan view from the thickness direction of the multilayer sheet 11, the length of the first ground electrode 31 in the direction along the Y-axis is longer than the length in the direction along the X-axis, for example. The first ground electrode 31 is disposed on the first main surface 14 of the multilayer sheet 11 so as to cover most of the first main surface 14 of the multilayer sheet 11, for example. The first ground electrode 31 is formed, for example, by patterning a second copper foil attached to the multilayer sheet that becomes the sheet 11a.

[0049] (1.4) Second ground electrode The second ground electrode 32 is disposed on the second main surface 15 of the multilayer sheet 11. The second ground electrode 32 corresponds to the conductor layer of the present disclosure. The second ground electrode 32 is in contact with the second main surface 15 of the multilayer sheet 11. The second ground electrode 32 faces the signal line 2 and the first ground electrode 31 in the thickness direction of the multilayer sheet 11.

[0050] The second ground electrode 32 has conductivity. The material of the second ground electrode 32 is, for example, copper. The second ground electrode 32 is formed in a predetermined pattern. In a plan view from the thickness direction of the multilayer sheet 11, the length of the second ground electrode 32 in the direction along the Y-axis is longer than the length in the direction along the X-axis, for example. The second ground electrode 32 is disposed on the second main surface 15 of the multilayer sheet 11 so as to cover most of the second main surface 15 of the multilayer sheet 11, for example. The second ground electrode 32 is formed, for example, by patterning a third copper foil attached to the multilayer sheet that becomes the sheet 11c.

[0051] (1.5) Resist layer Although not shown in FIGS. 1 and 2, the multilayer substrate 1 may include a first resist layer that covers the first main surface 14 of the multilayer sheet 11 and the first ground electrode 31.

[0052] Similarly, the multilayer substrate 1 may include a second resist layer that covers the second main surface 15 of the multilayer sheet 11 and the second ground electrode 32.

[0053] The first resist layer and the second resist layer include, for example, a polyimide film and an adhesive layer. The material of the adhesive layer includes, for example, an acrylic resin, a silicone resin, an epoxy resin, or a urethane resin. Note that the first resist layer or the second resist layer is not limited to a configuration including a polyimide film and an adhesive layer; for example, it may be a resist layer without an adhesive layer. The resist layer is formed, for example, using spin coating technology and photolithography technology.

[0054] (2) Characteristics of the multilayer sheet In the multilayer substrate 1 according to this embodiment, the sheet 11a is arranged between the signal line 2 and the first ground electrode 31 in the Z-axis direction, which is the stacking direction of the multilayer sheet 11.

[0055] In the multilayer substrate 1 according to this embodiment, the signal line 2 is elongated along the Y-axis. Furthermore, in sheet 11a, the second liquid crystal polymer sheet 13a is oriented in direction D11 along the Y-axis. In other words, the elongated direction of the signal line 2 is parallel to the first direction D11, which is the orientation axis of the second liquid crystal polymer sheet 13a. Note that the statement that the elongated direction of the signal line 2 is parallel to the first direction D11 includes not only the case where the elongated direction of the signal line 2 and the first direction D11 are strictly parallel, but also the case where, for 50% or more of the rod-shaped molecules, the angle between the elongated direction of the signal line 2 and the orientation direction of the rod-shaped molecules is 45 degrees or less.

[0056] In the second liquid crystal polymer sheet 13a, the liquid crystal polymer is oriented in direction D11, resulting in anisotropy in the dielectric constant. More specifically, in the second liquid crystal polymer sheet 13a, the dielectric constant in the Z-axis direction perpendicular to the orientation axis D11 is lower than the dielectric constant in the Y-axis direction along direction D11. Furthermore, the degree of orientation in the first liquid crystal polymer sheet 12a and the third liquid crystal polymer sheet 12b is smaller than that of the second liquid crystal polymer sheet 13a. Therefore, the dielectric constant of the first liquid crystal polymer sheet 12a and the third liquid crystal polymer sheet 12b is lower than that of the second liquid crystal polymer sheet 13a. Consequently, the dielectric constant in the Z-axis direction of the first liquid crystal polymer sheet 12a and the third liquid crystal polymer sheet 12b is higher than that of the second liquid crystal polymer sheet 13a in the Z-axis direction, and lower than that of the second liquid crystal polymer sheet 13a in the Y-axis direction.

[0057] As a result, the equivalent dielectric constant of sheet 11a in the Z-axis direction is lower than that of the first liquid crystal polymer sheet 12a in the Z-axis direction. Therefore, in the multilayer substrate 1 according to this embodiment, the parasitic capacitance generated between the signal line 2 and the first ground electrode 31 is smaller compared to the case where the entire sheet 11a is composed of the first liquid crystal polymer sheet 12a. Consequently, in the multilayer substrate 1 according to this embodiment, it is possible to reduce the loss of high-frequency signals transmitted by the signal line 2.

[0058] Similarly, the equivalent dielectric constant of sheet 11b in the Z-axis direction is lower than that of the first liquid crystal polymer sheet 12c in the Z-axis direction. Also, the equivalent dielectric constant of sheet 11c in the Z-axis direction is lower than that of the first liquid crystal polymer sheet 12c in the Z-axis direction. Therefore, the equivalent dielectric constant in the Z-axis direction of the sheet formed by laminating sheet 11b and sheet 11c is lower than that of the first liquid crystal polymer sheet 12c. As a result, in the multilayer substrate 1 according to this embodiment, it is possible to reduce the parasitic capacitance that occurs between the signal line 2 and the second ground electrode 32. Therefore, in the multilayer substrate 1 according to this embodiment, it is possible to reduce the loss of high-frequency signals transmitted by the signal line 2.

[0059] Furthermore, in sheet 11a, the dielectric constant of the second liquid crystal polymer sheet 13a in the X-axis direction is lower than that of the third liquid crystal polymer sheet 12b in the X-axis direction. Therefore, in the multilayer substrate 1 according to this embodiment, it is possible to reduce the parasitic capacitance that occurs between the signal line 2 and the third ground electrode 33, and the parasitic capacitance that occurs between the signal line 2 and the fourth ground electrode 34.

[0060] On the other hand, in the second liquid crystal polymer sheet 13a, the liquid crystal polymer is oriented in direction D11, so there is anisotropy in both tensile strength and peel strength. More specifically, in the second liquid crystal polymer sheet 13a, the tensile strength in the X-axis and Z-axis directions perpendicular to the orientation axis direction D11 is lower than the tensile strength in the Y-axis direction along the orientation axis. Also, in the second liquid crystal polymer sheet 13a, the peel strength in the X-axis and Z-axis directions perpendicular to the orientation axis direction D11 is lower than the peel strength in the Y-axis direction along the orientation axis. Therefore, when the second liquid crystal polymer sheet 13a is used instead of sheet 11a, the first ground electrode 31 becomes easier to peel off from the second liquid crystal polymer sheet 13a, and the signal line 2 and sheet 11b also become easier to peel off from the second liquid crystal polymer sheet 13a.

[0061] In contrast, the first liquid crystal polymer sheet 12a and the third liquid crystal polymer sheet 12b have a lower degree of orientation than the second liquid crystal polymer sheet 13a. Therefore, the first liquid crystal polymer sheet 12a and the third liquid crystal polymer sheet 12b have lower anisotropy in terms of tensile strength than the second liquid crystal polymer sheet 13a. Consequently, the tensile strength of sheet 11a in the X-axis direction is higher than that of the second liquid crystal polymer sheet 13a in the X-axis direction. In other words, the physical strength of sheet 11a is greater than that of the second liquid crystal polymer sheet 13a. Furthermore, the first ground electrode 31 is difficult to peel off from sheet 11a, and the signal line 2 and sheet 11b are also difficult to peel off from sheet 11a.

[0062] Furthermore, if the materials of the first liquid crystal polymer sheet 12a and the third liquid crystal polymer sheet 12b are the same as the material of the second liquid crystal polymer sheet 13a, the second liquid crystal polymer sheet 13a adheres more easily to the first liquid crystal polymer sheet 12a and the third liquid crystal polymer sheet 12b. As a result, delamination between the liquid crystal polymer sheet 12 and the liquid crystal polymer sheet 13 within sheet 11a is less likely to occur, thus further improving the physical strength of sheet 11a. Also, if the materials of the first liquid crystal polymer sheet 12c and the third liquid crystal polymer sheet 12d are the same as the material of the second liquid crystal polymer sheet 13b, the physical strength of sheet 11b can be further improved. Similarly, if the materials of the first liquid crystal polymer sheet 12e and the third liquid crystal polymer sheet 12f are the same as the material of the second liquid crystal polymer sheet 13c, the physical strength of sheet 11c can be further improved.

[0063] (3) The electronic device 500 according to the first embodiment of the electronic device comprises a multilayer substrate module 400 and a housing 501 that houses the multilayer substrate module 400, as shown in Figure 4. The multilayer substrate module 400 comprises a multilayer substrate 1 and a plurality of connectors 410 (two in the example of Figure 4).

[0064] The electronic device 500 further comprises a first printed circuit board 504, a second printed circuit board 505, a connector 514 mounted on the first printed circuit board 504, and a connector 515 mounted on the second printed circuit board 505. A battery 503, which serves as the power source for the electronic device 500, is housed within the housing 501 of the electronic device 500.

[0065] In the electronic device 500, one of the two connectors 410 of the multilayer circuit board module 400 is connected to connector 514, and the other connector 410 is connected to connector 515. As a result, in the electronic device 500, the first printed circuit board 504 and the second printed circuit board 505 are connected via the multilayer circuit board module 400. In the electronic device 500, the multilayer circuit board 1 of the multilayer circuit board module 400 is housed in the housing 501 in a bent state.

[0066] A signal processing circuit for processing high-frequency signals is arranged on at least one of the first printed circuit board 504 and the second printed circuit board 505. That is, the electronic device 500 includes a signal processing circuit connected to the signal line 2 on at least one of the first printed circuit board 504 and the second printed circuit board 505.

[0067] (4) Effect The multilayer sheet 11 according to Embodiment 1 comprises first liquid crystal polymer sheets 12a, 12c, and 12e, second liquid crystal polymer sheets 13a, 13b, and 13c, and third liquid crystal polymer sheets 12b, 12d, and 12f. The second liquid crystal polymer sheets 13a, 13b, and 13c contain a liquid crystal polymer as a material and are oriented in first directions D11, D21, and D31 perpendicular to the thickness direction of the multilayer sheet 11. Each of the first liquid crystal polymer sheets 12a, 12c, and 12e and the third liquid crystal polymer sheets 12b, 12d, and 12f contains a liquid crystal polymer as a material and has a lower degree of orientation than the second liquid crystal polymer sheets 13a, 13b, and 13c. In the thickness direction of the multilayer sheet 11, each of the second liquid crystal polymer sheets 13a, 13b, and 13c is sandwiched between one of the first liquid crystal polymer sheets 12a, 12c, and 12e and one of the third liquid crystal polymer sheets 12b, 12d, and 12f.

[0068] According to the above configuration, it is possible to improve the physical strength and physical properties of the multilayer sheet 11 according to Embodiment 1. In the multilayer substrate 1 according to Embodiment 1, for example, it is possible to make the equivalent dielectric constant of sheet 11a of the multilayer sheet 11 greater than one of the dielectric constants of the second liquid crystal polymer sheet 13a and the dielectric constant of the first liquid crystal polymer sheet 12a and less than the other. In addition, in the multilayer substrate 1 according to Embodiment 1, for example, it is possible to make the equivalent dielectric constant of the multilayer sheet 11 different in a specific direction and in a direction orthogonal to that specific direction. Furthermore, in the multilayer sheet 11 according to Embodiment 1, it is possible to improve the mechanical strength of the multilayer sheet 11 compared to the case in which the first liquid crystal polymer sheets 12a, 12c, and 12e and the third liquid crystal polymer sheets 12b, 12d, and 12f are not included.

[0069] Furthermore, the multilayer substrate 1 according to Embodiment 1 comprises a multilayer sheet 11 and a first ground electrode 31 and a second ground electrode 32 which are conductive layers. The first ground electrode 31 is located on the first main surface 14 of the multilayer sheet 11. The second ground electrode 32 is located on the second main surface 15 of the multilayer sheet 11.

[0070] According to the above configuration, one or more of the first liquid crystal polymer sheets 12a, 12c, and 12e and the third liquid crystal polymer sheets 12b, 12d, and 12f are present between the first ground electrode 31 and the second ground electrode 32 and the second liquid crystal polymer sheets 13a, 13b, and 13c. Since the peel strength of the first liquid crystal polymer sheets 12a, 12c, and 12e and the third liquid crystal polymer sheets 12b, 12d, and 12f is higher than that of the second liquid crystal polymer sheets 13a, 13b, and 13c, the multilayer substrate 1 according to Embodiment 1 has high physical strength.

[0071] Furthermore, the multilayer substrate 1 according to Embodiment 1 comprises a multilayer sheet 11 and a signal line 2. The signal line 2 is arranged on the first main surface 14, the second main surface 15, or inside the multilayer sheet 11.

[0072] With the above configuration, it becomes easy to make the dielectric constant between the signal line 2 and the electrodes (for example, the first ground electrode 31) arranged inside the multilayer sheet 11 or on the first main surface 14 and the second main surface 15 greater than one of the dielectric constants of the second liquid crystal polymer sheets 13a, 13b, and 13c and less than the dielectric constants of the first liquid crystal polymer sheets 12a, 12c, and 12e.

[0073] Furthermore, in the multilayer substrate 1 according to Embodiment 1, the longitudinal direction of the signal line 2 is parallel to the first directions D11, D21, and D31, which are the orientation directions of the second liquid crystal polymer sheets 13a, 13b, and 13c.

[0074] According to the above configuration, the dielectric constant of the second liquid crystal polymer sheets 13a, 13b, and 13c is high in the longitudinal direction of the signal line 2 and low in the direction perpendicular to the longitudinal direction of the signal line 2. Therefore, it is possible to lower the dielectric constant between the signal line 2 and the electrodes (for example, the first ground electrode 31) located inside the multilayer substrate 1 or on the first main surface 14 and the second main surface 15. As a result, when the signal line 2 transmits a high-frequency signal, it is possible to reduce the loss of the high-frequency signal.

[0075] Furthermore, the electronic device 500 according to Embodiment 1 comprises a multilayer substrate 1 and a first printed circuit board 504 and a second printed circuit board 505, which are signal processing circuits connected to a signal line 2.

[0076] According to the above configuration, it becomes easier to reduce the loss of high-frequency signals in the signal line 2 in the electronic device 500.

[0077] (Embodiment 2) The multilayer substrate 1a according to Embodiment 2 will be described with reference to Figure 5. With respect to the multilayer substrate 1a according to Embodiment 2, components that are the same as those in the multilayer substrate 1 according to Embodiment 1 (see Figures 1 to 3) are denoted by the same reference numerals and their description is omitted.

[0078] (1) The multilayer substrate 1a according to the second embodiment differs from the multilayer substrate 1 according to the first embodiment (see Figure 3) in that, as shown in Figure 5, the orientation axis of the second liquid crystal polymer sheet is aligned with the X-axis direction which is perpendicular to the Y-axis direction which is the longitudinal direction of the signal line 2.

[0079] As shown in Figure 5, the multilayer substrate 1a according to Embodiment 2 includes sheets 11d, 11e, and 11f instead of sheets 11a, 11b, and 11c (see Figure 1). Sheet 11d includes a second liquid crystal polymer sheet 13d instead of a second liquid crystal polymer sheet 13a (see Figures 1 and 3). Sheet 11e includes a second liquid crystal polymer sheet 13e instead of a second liquid crystal polymer sheet 13b (see Figures 1 and 3). Sheet 11f includes a second liquid crystal polymer sheet 13f instead of a second liquid crystal polymer sheet 13c (see Figures 1 and 3).

[0080] As shown in Figure 5, the orientation axes of the second liquid crystal polymer sheets 13d, 13e, and 13f are different from those of the second liquid crystal polymer sheets 13a, 13b, and 13c (see Figure 3). The second liquid crystal polymer sheet 13d is oriented in direction D12 along the X-axis direction. The second liquid crystal polymer sheet 13e is oriented in direction D22 along the X-axis direction. The second liquid crystal polymer sheet 13f is oriented in direction D32 along the X-axis direction. That is, directions D12, D22, and D32 correspond to the first direction of this disclosure. In other words, in the multilayer substrate 1a according to Embodiment 2, the longitudinal direction of the signal line 2 is along the directions D12, D22, and D32, which are the orientation axes of the plurality of second liquid crystal polymer sheets 13d, 13e, and 13f, and along the Y-axis direction which is perpendicular to the Z-axis direction, which is the thickness direction of the multilayer sheet 11. "The longitudinal direction of the signal line 2 is aligned with the Y-axis direction which is perpendicular to the Z-axis direction, which is the thickness direction of the multilayer sheet 11, and is the orientation axis of the multiple second liquid crystal polymer sheets 13d, 13e, and 13f, respectively, which are directions D12, D22, and D32." This includes not only the case where the longitudinal direction of the signal line 2 and the Y-axis direction are strictly parallel, but also the case where the angle between the longitudinal direction of the signal line 2 and the Y-axis direction is 10 degrees or less.

[0081] In the multilayer substrate 1a according to this embodiment, the dielectric constant of the second liquid crystal polymer sheet 13a in the Y-axis direction and the Z-axis direction is lower than the dielectric constant of the second liquid crystal polymer sheet 13a in the X-axis direction. Similarly, the dielectric constant of the second liquid crystal polymer sheet 13b in the Y-axis direction and the Z-axis direction is lower than the dielectric constant of the second liquid crystal polymer sheet 13b in the X-axis direction. Similarly, the dielectric constant of the second liquid crystal polymer sheet 13c in the Y-axis direction and the Z-axis direction is lower than the dielectric constant of the second liquid crystal polymer sheet 13c in the X-axis direction.

[0082] Therefore, in the multilayer substrate 1a according to this embodiment, the parasitic capacitance between the signal line 2 and the first ground electrode 31 is larger compared to the case where a first liquid crystal polymer sheet 12a of the same thickness as sheet 11d is provided instead of sheet 11d. Similarly, in the multilayer substrate 1a according to this embodiment, the parasitic capacitance between the signal line 2 and the second ground electrode 32 is larger compared to the case where a first liquid crystal polymer sheet 12c of the same thickness as sheet 11e and a first liquid crystal polymer sheet 12e of the same thickness as sheet 11f are provided instead of sheets 11e and 11f. Similarly, in the multilayer substrate 1a according to this embodiment, the parasitic capacitance between the signal line 2 and the third ground electrode 33 is larger compared to the case where a first liquid crystal polymer sheet 12a of the same thickness as sheet 11d is provided instead of sheet 11d. Similarly, in the multilayer substrate 1a according to this embodiment, the parasitic capacitance between the signal line 2 and the fourth ground electrode 34 is larger compared to the case where a first liquid crystal polymer sheet 12a of the same thickness as sheet 11d is provided instead of sheet 11d.

[0083] On the other hand, in the multilayer substrate 1a according to this embodiment, each of the sheets 11d, 11e, and 11f has a lower equivalent dielectric constant in the Y-axis direction, which is the direction in which the high-frequency signal is transmitted through the signal line 2, compared to the case in which the first liquid crystal polymer sheet 12a, the first liquid crystal polymer sheet 12c, and the first liquid crystal polymer sheet 12e are provided.

[0084] In the multilayer substrate 1a according to this embodiment, the equivalent dielectric constant in the Y-axis direction along the direction in which the high-frequency signal is transmitted through the signal line 2 is low in the sheet 11d adjacent to the signal line 2, and the equivalent dielectric constant in the X-axis and Z-axis directions perpendicular to the direction in which the high-frequency signal is transmitted through the signal line 2 is high, thereby making it possible to improve the signal propagation speed.

[0085] (2) In the multilayer substrate 1a according to the second embodiment, the Y-axis direction, which is the longitudinal direction of the signal line 2, is aligned with directions D12, D22 and D32, which are the orientation axes of the plurality of second liquid crystal polymer sheets 13d, 13e and 13f, and directions perpendicular to the thickness direction of the multilayer sheet 11.

[0086] According to the above configuration, the equivalent dielectric constant of the multilayer sheet 11 is low in the direction along the longitudinal direction of the signal line 2 and high in the direction perpendicular to the longitudinal direction of the signal line 2. This makes it possible to improve the signal propagation speed of high-frequency signals when the signal line 2 transmits high-frequency signals.

[0087] (Embodiment 3) The multilayer substrate 1b according to Embodiment 3 will be described with reference to Figures 6 to 8. With respect to the multilayer substrate 1b according to Embodiment 3, components that are the same as those in the multilayer substrate 1 according to Embodiment 1 (see Figures 1 to 3) are denoted by the same reference numerals and their description is omitted.

[0088] (1) The multilayer substrate 1b according to the configuration embodiment 3 differs from the multilayer substrate 1 according to embodiment 1 (see Figure 1) in that, as shown in Figure 6, it is equipped with a signal line 35, a connecting conductor 36, and a radiating electrode 31a instead of the signal line 2 and the first ground electrode 31.

[0089] As shown in Figure 6, the multilayer substrate 1a according to Embodiment 3 comprises sheets 11g, 11h, and 11i instead of sheets 11a, 11b, and 11c (see Figure 1). Sheet 11g comprises a second liquid crystal polymer sheet 13g instead of a second liquid crystal polymer sheet 13a (see Figures 1 and 3). Sheet 11h comprises a second liquid crystal polymer sheet 13h instead of a second liquid crystal polymer sheet 13b (see Figures 1 and 3). Sheet 11i comprises a second liquid crystal polymer sheet 13i instead of a second liquid crystal polymer sheet 13c (see Figures 1 and 3).

[0090] As shown in Figure 8, the second liquid crystal polymer sheet 13g is oriented in direction D13 along the Y-axis. As shown in Figure 8, the second liquid crystal polymer sheet 13h is oriented in direction D23 along the Y-axis. As shown in Figure 8, the second liquid crystal polymer sheet 13i is oriented in direction D33 along the Y-axis. Directions D13, D23, and D33 correspond to the first direction of this disclosure. In other words, the orientation axes of the plurality of second liquid crystal polymer sheets 13d, 13e, and 13f, which are directions D13, D23, and D33, are all along the Y-axis.

[0091] The signal line 35 is located within the multilayer sheet 11. More specifically, as shown in Figure 6, the signal line 35 is located on the main surface of sheet 11h and is in contact with the main surface of sheet 11g. The signal line 35 has a length along the Y-axis that is longer than its length along the X-axis.

[0092] The radiating electrode 31a is positioned on the first main surface 14 (see Figure 1) of the multilayer sheet 11. The radiating electrode 31a corresponds to the conductive layer of this disclosure. The radiating electrode 31a is in contact with the first main surface 14 of the multilayer sheet 11. In the thickness direction of the multilayer sheet 11, the radiating electrode 31a faces the second ground electrode 32.

[0093] The radiating electrode 31a is conductive. As shown in Figures 6 and 7, the first ground electrode 31 has a slit 311. As shown in Figure 7, the length of the slit 311 in the direction along the X axis is longer than the length in the direction along the Y axis. In this embodiment, the radiating electrode 31a, the second ground electrode 32, and the multilayer sheet 11 constitute a slot antenna.

[0094] As shown in Figure 6, the connecting conductor 36 penetrates the sheet 11g and is connected to the radiating electrode 31a. The connecting conductor 36 connects the signal line 35 and the radiating electrode 31a.

[0095] In this embodiment, the orientation axes of the multiple second liquid crystal polymer sheets 13d, 13e, and 13f, which are directions D13, D23, and D33 respectively, are perpendicular to the longitudinal direction of the slit 311. "Directions D13, D23, and D33 are perpendicular to the longitudinal direction of the slit 311" includes not only cases where directions D13, D23, and D33 are strictly perpendicular to the longitudinal direction of the slit 311, but also cases where the angle between directions D13, D23, or D33 and the longitudinal direction of the slit 311 is 80 degrees or more and 100 degrees or less. Therefore, in the multilayer sheet 11, the equivalent dielectric constant in the X-axis direction, which is the longitudinal direction of the slit 311, is lower than the equivalent dielectric constant in the Y-axis direction, which is the width direction of the slit 311. Therefore, in the multilayer substrate 1b according to Embodiment 3, it is possible to shorten the length of the slit 311 in the X-axis direction. Therefore, it is possible to miniaturize the multilayer substrate 1b by reducing the area of ​​the radiating electrode 31a.

[0096] (2) The multilayer substrate 1b according to the third embodiment further comprises a radiating electrode 31a which is a conductive layer. The radiating electrode 31a is arranged on the first main surface 14 of the multilayer sheet 11.

[0097] According to the above configuration, one or more of the first liquid crystal polymer sheets 12a, 12c, and 12e and the third liquid crystal polymer sheets 12b, 12d, and 12f are present between the radiating electrode 31a and the second liquid crystal polymer sheets 13d, 13e, and 13f. Since the peel strength of the first liquid crystal polymer sheets 12a, 12c, and 12e and the third liquid crystal polymer sheets 12b, 12d, and 12f is higher than that of the second liquid crystal polymer sheets 13d, 13e, and 13f, the multilayer substrate 1 according to Embodiment 1 has high physical strength.

[0098] (Embodiment 4) The multilayer sheet 11 and multilayer substrate 1c according to Embodiment 4 will be described with reference to Figure 9. With respect to the multilayer substrate 1c according to Embodiment 4, components that are the same as those in the multilayer sheet 11 and multilayer substrate 1 according to Embodiment 1 (see Figures 1 to 3) are denoted by the same reference numerals and their description is omitted.

[0099] (1) In the multilayer sheet 11 and multilayer substrate 1c according to Embodiment 4, as shown in Figure 9, the relationship between the thickness of the first liquid crystal polymer sheet 12c, the thickness of the second liquid crystal polymer sheet 13b, and the thickness of the third liquid crystal polymer sheet 12d in the sheet 11b is different from the relationship between the thicknesses in the multilayer sheet 11 according to Embodiment 1 (see Figure 1).

[0100] In the multilayer substrate 1c according to Embodiment 4, the thickness of the first liquid crystal polymer sheet 12c is d1. The thickness of the second liquid crystal polymer sheet 13b is d2. The thickness of the third liquid crystal polymer sheet 12d is d3.

[0101] The thickness d2 of the second liquid crystal polymer sheet 13b is preferably 20% or more of the thickness of sheet 11b. This ensures that the ratio of the equivalent dielectric constant of the multilayer sheet 11 in the direction along direction D12 to the dielectric constant of the first liquid crystal polymer sheet 12c is sufficiently greater than 1. Furthermore, the ratio of the equivalent dielectric constant of the multilayer sheet 11 in the direction perpendicular to direction D12 to the dielectric constant of the first liquid crystal polymer sheet 12c is sufficiently less than 1. Therefore, it becomes possible to utilize the multilayer sheet 11 as a sheet having an equivalent dielectric constant different from that of the first liquid crystal polymer sheet 12c. Additionally, since the anisotropy of the equivalent dielectric constant is increased in the multilayer sheet 11, the multilayer sheet 11 can be utilized as a sheet with anisotropy.

[0102] It is preferable that the thickness d1 of the first liquid crystal polymer sheet 12c and the thickness d3 of the third liquid crystal polymer sheet 12d are the same. "The thickness d1 of the first liquid crystal polymer sheet 12c and the thickness d3 of the third liquid crystal polymer sheet 12d are the same" includes not only cases where the thickness d1 of the first liquid crystal polymer sheet 12c and the thickness d3 of the third liquid crystal polymer sheet 12d are strictly the same, but also cases where the ratio of the thickness d1 of the first liquid crystal polymer sheet 12c to the thickness d3 of the third liquid crystal polymer sheet 12d is 0.9 or more and 1.1 or less.

[0103] By changing the ratio of the thickness d2 of the second liquid crystal polymer sheet 13b to the thickness d1 of the first liquid crystal polymer sheet 12c, it is possible to change the equivalent dielectric constant of the multilayer sheet 11. As described above, the dielectric constant of the first liquid crystal polymer sheet 12c has low anisotropy, while the dielectric constant of the second liquid crystal polymer sheet 13b has high anisotropy. Furthermore, if the material of the first liquid crystal polymer sheet 12c and the material of the second liquid crystal polymer sheet 13b are the same, the dielectric constant of the first liquid crystal polymer sheet 12c is higher than the dielectric constant of the second liquid crystal polymer sheet 13b in the direction perpendicular to direction D21, and lower than the dielectric constant of the second liquid crystal polymer sheet 13b along direction D21, in all directions. Below, as a specific example, we will describe the case where the relative dielectric constant of the first liquid crystal polymer sheet 12c is 4.0 in all directions, and the relative dielectric constant of the second liquid crystal polymer sheet 13b in the direction perpendicular to direction D21 is 2.8.

[0104] Therefore, by designing the sheet with a small ratio of the thickness d2 of the second liquid crystal polymer sheet 13b to the thickness d1 of the first liquid crystal polymer sheet 12c, it is possible to bring the equivalent dielectric constant of the sheet 11b in the direction perpendicular to the direction D21 closer to the dielectric constant of the first liquid crystal polymer sheet 12c. On the other hand, by designing the sheet with a large ratio of the thickness d2 of the second liquid crystal polymer sheet 13b to the thickness d1 of the first liquid crystal polymer sheet 12c, it is possible to bring the equivalent dielectric constant of the sheet 11b in the direction perpendicular to the direction D21 closer to the dielectric constant of the second liquid crystal polymer sheet 13b in the direction perpendicular to the direction D21. In other words, in the specific example described above, the smaller the ratio of the thickness d2 of the second liquid crystal polymer sheet 13b to the thickness d1 of the first liquid crystal polymer sheet 12c, the closer the equivalent relative dielectric constant of the sheet 11b in the direction perpendicular to the direction D21 is to 4.0. Furthermore, the larger the ratio of the thickness d2 of the second liquid crystal polymer sheet 13b to the thickness d1 of the first liquid crystal polymer sheet 12c, the closer the equivalent relative permittivity in the direction perpendicular to the direction D21 of sheet 11b is to 2.8. Therefore, by appropriately designing the ratio of the thickness d2 of the second liquid crystal polymer sheet 13b to the thickness d1 of the first liquid crystal polymer sheet 12c, it is possible to set the equivalent relative permittivity in the direction perpendicular to the direction D21 of sheet 11b to a desired value greater than 2.8 and lower than 4.0.

[0105] Similarly, the equivalent dielectric constant of sheet 11b in the direction D21 also changes according to the ratio of the thickness d2 of the second liquid crystal polymer sheet 13b to the thickness d1 of the first liquid crystal polymer sheet 12c. By designing the ratio of the thickness d2 of the second liquid crystal polymer sheet 13b to the thickness d1 of the first liquid crystal polymer sheet 12c to be small, it is possible to bring the equivalent dielectric constant of sheet 11b in the direction D21 close to the dielectric constant of the first liquid crystal polymer sheet 12c. On the other hand, by designing the ratio of the thickness d2 of the second liquid crystal polymer sheet 13b to the thickness d1 of the first liquid crystal polymer sheet 12c to be large, it is possible to bring the equivalent dielectric constant of sheet 11b in the direction D21 close to the dielectric constant of the second liquid crystal polymer sheet 13b in the direction D21. In other words, in the specific example described above, the smaller the ratio of the thickness d2 of the second liquid crystal polymer sheet 13b to the thickness d1 of the first liquid crystal polymer sheet 12c, the closer the equivalent relative permittivity in the direction perpendicular to the direction D21 of sheet 11b is to 4.0, and the larger the ratio of the thickness d2 of the second liquid crystal polymer sheet 13b to the thickness d1 of the first liquid crystal polymer sheet 12c, the larger the equivalent relative permittivity in the direction perpendicular to the direction D21 of sheet 11b.

[0106] The thickness d2 of the second liquid crystal polymer sheet 13b is preferably at least half the thickness d1 of the first liquid crystal polymer sheet 12c. As a result, the thickness d2 of the second liquid crystal polymer sheet 13b is at least 20% of the thickness of sheet 11b. Therefore, anisotropy occurs in the equivalent dielectric constant of sheet 11b, and the equivalent dielectric constant of sheet 11b in the direction along the orientation axis D21 of the second liquid crystal polymer sheet 13b is smaller than the equivalent dielectric constant of sheet 11b in the direction perpendicular to direction D21.

[0107] Furthermore, it is preferable that the thickness d2 of the second liquid crystal polymer sheet 13b is 100 times or less the thickness d1 of the first liquid crystal polymer sheet 12c. In order to improve the physical strength of the multilayer sheet 11, the minimum values ​​of the thickness d1 of the first liquid crystal polymer sheet 12c and the thickness d3 of the third liquid crystal polymer sheet 12d are 1 / 100 times the thickness d2 of the second liquid crystal polymer sheet 13b.

[0108] (2) Effect: In the multilayer sheet 11 according to Embodiment 4, the thickness d2 of the second liquid crystal polymer sheet 13b is 1 / 2 to 100 times the thickness d1 of the first liquid crystal polymer sheet 12c.

[0109] According to the above configuration, the physical strength of the multilayer sheet 11 can be improved, and the equivalent dielectric constant of the multilayer sheet 11 can be set to a value corresponding to the ratio of the thickness d2 of the second liquid crystal polymer sheet 13b to the thickness d1 of the first liquid crystal polymer sheet 12c.

[0110] (Modified Versions) A modified version of Embodiment 4, consisting of a multilayer sheet 11 and a multilayer substrate 1d, will be described with reference to Figure 10. With respect to the multilayer substrate 1d of the modified version of Embodiment 4, components similar to those in the multilayer substrate 1b of Embodiment 3 (see Figures 6 to 8) are denoted by the same reference numerals and their description is omitted.

[0111] (1) In the multilayer substrate 1d according to a modified example of the configuration embodiment 4, as shown in Figure 10, the relationship between the thickness of the first liquid crystal polymer sheet 12a, the thickness of the second liquid crystal polymer sheet 13g, and the thickness of the third liquid crystal polymer sheet 12b in the sheet 11g is different from the relationship in the multilayer substrate 1b according to embodiment 3 (see Figure 6).

[0112] In the multilayer substrate 1d according to a modified example of Embodiment 4, the thickness of the first liquid crystal polymer sheet 12a is d4. The thickness of the second liquid crystal polymer sheet 13g is d5. The thickness of the third liquid crystal polymer sheet 12b is d6.

[0113] The thickness d5 of the second liquid crystal polymer sheet 13g is preferably 20% or more of the thickness of the sheet 11g.

[0114] It is preferable that the thickness d4 of the first liquid crystal polymer sheet 12a and the thickness d6 of the third liquid crystal polymer sheet 12b are the same. "The thickness d4 of the first liquid crystal polymer sheet 12a and the thickness d6 of the third liquid crystal polymer sheet 12b are the same" includes not only the case where the thickness d4 of the first liquid crystal polymer sheet 12a and the thickness d6 of the third liquid crystal polymer sheet 12b are strictly the same, but also the case where the ratio of the thickness d4 of the first liquid crystal polymer sheet 12a to the thickness d6 of the third liquid crystal polymer sheet 12b is 0.9 or more and 1.1 or less.

[0115] Here, by changing the ratio of the thickness d5 of the second liquid crystal polymer sheet 13g to the thickness d4 of the first liquid crystal polymer sheet 12a, it is possible to change the equivalent dielectric constant of the multilayer sheet 11.

[0116] Therefore, by designing the ratio of the thickness d5 of the second liquid crystal polymer sheet 13g to the thickness d4 of the first liquid crystal polymer sheet 12a to be small, it is possible to bring the equivalent dielectric constant of the sheet 11g in the direction perpendicular to direction D13 close to that of the first liquid crystal polymer sheet 12c. On the other hand, by designing the ratio of the thickness d5 of the second liquid crystal polymer sheet 13g to the thickness d4 of the first liquid crystal polymer sheet 12a to be large, it is possible to bring the equivalent dielectric constant of the sheet 11g in the direction perpendicular to direction D13 close to that of the second liquid crystal polymer sheet 13g in the direction perpendicular to direction D13. For example, similar to Embodiment 3, when the longitudinal direction of the slit 311 and direction D13 are perpendicular, by designing the ratio of the thickness d5 of the second liquid crystal polymer sheet 13g to the thickness d4 of the first liquid crystal polymer sheet 12a to be large, it is possible to shorten the length of the slit 311 in the longitudinal direction.

[0117] Similarly, the equivalent dielectric constant of sheet 11g in the direction D13 also changes depending on the ratio of the thickness d5 of the second liquid crystal polymer sheet 13g to the thickness d4 of the first liquid crystal polymer sheet 12a. When the ratio of the thickness d5 of the second liquid crystal polymer sheet 13g to the thickness d4 of the first liquid crystal polymer sheet 12a is small, the equivalent dielectric constant of sheet 11g in the direction D13 is close to the dielectric constant of the first liquid crystal polymer sheet 12a. On the other hand, when the ratio of the thickness d5 of the second liquid crystal polymer sheet 13g to the thickness d4 of the first liquid crystal polymer sheet 12a is large, the equivalent dielectric constant of sheet 11g in the direction D13 is close to the dielectric constant of the second liquid crystal polymer sheet 13g in the direction D13.

[0118] The thickness d2 of the second liquid crystal polymer sheet 13b is preferably at least half the thickness d1 of the first liquid crystal polymer sheet 12c. Furthermore, the thickness d2 of the second liquid crystal polymer sheet 13b is preferably 100 times or less the thickness d1 of the first liquid crystal polymer sheet 12c.

[0119] (2) Effect: In the multilayer sheet 11 according to a modified example of Embodiment 4, the thickness d5 of the second liquid crystal polymer sheet 13g is 1 / 2 to 100 times the thickness d4 of the first liquid crystal polymer sheet 12a.

[0120] According to the above configuration, the physical strength of the multilayer sheet 11 can be improved, and the equivalent dielectric constant of the multilayer sheet 11 can be set to a value corresponding to the ratio of the thickness d5 of the second liquid crystal polymer sheet 13g to the thickness d4 of the first liquid crystal polymer sheet 12a.

[0121] (Embodiment 5) The multilayer sheet 11, soundboard 610, and musical instrument 600 according to Embodiment 5 will be described with reference to Figures 11 and 12. With respect to the multilayer sheet 11 according to Embodiment 5 (see Figure 12), components that are the same as those in the multilayer sheet 11 according to Embodiment 1 (see Figures 1 to 3) are denoted by the same reference numerals and their description is omitted.

[0122] (1) The multilayer sheet 11 according to Embodiment 5 (see Figure 12) comprises sheets 11a, 11b and 11c (see Figure 1), similar to the multilayer sheet 11 according to Embodiment 1 (see Figure 1).

[0123] As shown in Figure 11, the multilayer sheet 11 is used in the soundboard 610 of the musical instrument 600 according to Embodiment 5. The musical instrument 600 comprises the soundboard 610 and the sound source 630. As shown in Figure 12, the soundboard 610 comprises the multilayer sheet 11 and the support plate 611. In this embodiment, the musical instrument 600 is a stringed instrument equipped with a sound source 630 which is a string, and specifically it is a guitar. However, the musical instrument 600 is not limited to instruments that require human operation, as long as it is equipped with a soundboard 610 and a sound source 630 and has a sound-producing function. The musical instrument 600 may be, for example, an automatic musical instrument such as a music box, or an audio device such as a speaker.

[0124] The instrument 600 according to this embodiment further includes a bridge 620 connecting the sound source 630 and the soundboard 610, and a sound hole 640. Note that the sound hole 640 is omitted in Figure 12.

[0125] The multilayer sheet 11 is placed on the support plate 611. The multilayer sheet 11 is attached to the main surface of the support plate 611. The multilayer sheet 11 is attached to the support plate 611, for example, via an adhesive. Alternatively, the multilayer sheet 11 may be heat-pressed to the support plate 611, for example.

[0126] As shown in Figure 1, sheet 11a includes a first liquid crystal polymer sheet 12a, a second liquid crystal polymer sheet 13a, and a third liquid crystal polymer sheet 12b. Sheet 11b includes a first liquid crystal polymer sheet 12c, a second liquid crystal polymer sheet 13b, and a third liquid crystal polymer sheet 12d. Sheet 11c includes a first liquid crystal polymer sheet 12e, a second liquid crystal polymer sheet 13c, and a third liquid crystal polymer sheet 12f.

[0127] The second liquid crystal polymer sheet 13a, the second liquid crystal polymer sheet 13b, and the second liquid crystal polymer sheet 13c are all oriented in a direction D14 (see Figure 12) perpendicular to the thickness direction of the multilayer sheet 11. Direction D14 corresponds to the first direction of this disclosure. Direction D14 is parallel to the string which is the sound source 630.

[0128] As described above, in the liquid crystal polymer sheet 13, since the liquid crystal polymer is oriented in direction D14, the elastic modulus, such as Young's modulus, is also anisotropic. More specifically, in the liquid crystal polymer sheet 13, the elastic modulus along the orientation axis direction D14 is higher than the elastic modulus along the direction perpendicular to direction D14. Therefore, when the multilayer sheet 11 and the sound source 630 are in contact, or when the multilayer sheet 11 is facing the sound source 630 in a direction perpendicular to direction D14, sound propagates through the multilayer sheet 11 in the direction D14 at high speed. Consequently, the multilayer sheet 11 has acoustic properties similar to those of a straight-grained wooden board, where the grain is parallel to direction D14. Furthermore, in the musical instrument 600 according to Embodiment 5, since sound is propagated by the multilayer sheet 11 in the soundboard 610, even if a flat-grained wooden board is used for the support plate 611, it is possible to reduce the deterioration of acoustic properties.

[0129] In this embodiment, vibrations generated in the sound source 630 are transmitted to the soundboard 610 via the bridge 620. In the direction along direction D14, the elastic modulus of the liquid crystal polymer sheet 13 is higher than that of the liquid crystal polymer sheet 12. Therefore, sound propagating from the bridge 620 in direction D14 propagates rapidly through the liquid crystal polymer sheet 13. In other words, in the instrument 600 according to this embodiment, sound emitted from the sound source 630 propagates in direction D14.

[0130] In this embodiment, the instrument 600 is a guitar, but it may be any other type of stringed instrument such as a violin, cello, or piano, and the same effect can be achieved by aligning the liquid crystal polymer sheet 13 parallel to the strings. Also, the sound source 630 may be a sound-producing element.

[0131] (2) The soundboard 610 according to the effect embodiment 5 comprises a support plate 611 and a multilayer sheet 11. The multilayer sheet 11 is arranged on the support plate 611.

[0132] According to the above configuration, the elastic modulus of the soundboard 610 in direction D14, which is the orientation axis of the second liquid crystal polymer sheets 13a, 13b, and 13c, is lower than the elastic modulus of the soundboard 610 in the direction perpendicular to direction D14. Therefore, the soundboard 610 has acoustic properties similar to those of a straight-grained wooden board whose grain is parallel to direction D14.

[0133] The musical instrument 600 according to Embodiment 5 comprises a soundboard 610 and a sound source 630. Sound emitted from the sound source 630 propagates in the direction D14, which is the orientation axis.

[0134] According to the above configuration, when sound emitted from the sound source 630 propagates through the soundboard 610, it propagates along the orientation axes of the second liquid crystal polymer sheets 13a, 13b, and 13c. Therefore, in the instrument 600, similar to the case where a straight-grained wooden board with the grain parallel to direction D14 is used as the soundboard, the direction in which sound primarily propagates can be set to a desired direction, making it easy to achieve high sound quality.

[0135] (Modifications) Embodiments 1 to 5 described above are merely one of many embodiments of the present invention. Embodiments 1 to 5 described above can be modified in various ways depending on the design, etc., as long as the objective of the present invention is achieved, and may be combined as appropriate.

[0136] For example, the multilayer sheet 11 may comprise only the second liquid crystal polymer sheet 13a among a plurality of second liquid crystal polymer sheets 13a, 13b, and 13c. Alternatively, the multilayer sheet 11 may comprise four or more second liquid crystal polymer sheets.

[0137] Furthermore, if the multilayer substrate 1 includes strip lines, it is preferable to provide a second liquid crystal polymer sheet between the signal line 2 and each of the first ground electrode 31 and the second ground electrode 32.

[0138] Furthermore, the multilayer substrate 1 may not have a second ground electrode 32 and may include microstrip lines.

[0139] Furthermore, in the multilayer sheet 11, only one first liquid crystal polymer sheet 12c may be placed between the second liquid crystal polymer sheet 13a and the second liquid crystal polymer sheet 13b.

[0140] Furthermore, in the multilayer substrate 1b, the radiating electrode 31a does not need to have a slit 311, and the radiating electrode 31a may have any shape.

[0141] Furthermore, in the multilayer substrate 1, the signal line 2 may be a differential line.

[0142] Furthermore, in the multilayer sheet 11 and the multilayer substrate 1, the materials of the liquid crystal polymer sheet 12 and the liquid crystal polymer sheet 13 are not limited to thermoplastic liquid crystal polymers, but may be thermosetting liquid crystal epoxy polymers or photocurable liquid crystal epoxy polymers.

[0143] 1, 1a, 1b, 1c, 1d Multilayer substrate 11 Multilayer sheet 11a, 11b, 11c, 11d, 11e, 11f, 11g, 11h, 11i Sheet 111a, 111b, 111c First main surface of sheet 112a, 112b, 112c Second main surface of sheet 12 Liquid crystal polymer sheet 12a, 12c, 12e First liquid crystal polymer sheet 12b, 12d, 12f Third liquid crystal polymer sheet 13 Liquid crystal polymer sheet 13a, 13b, 13c, 13d, 13e, 13f, 13g, 13h, 13i Second liquid crystal polymer sheet 14 First main surface (main surface) 15 Second main surface (main surface) 2, 35 Signal line 31 First ground electrode 31a Radiation electrode 311 Slit 32 Second ground electrode 33 Third ground electrode 34 Fourth ground electrode 36 Connecting conductor 400 Multilayer circuit board module 410 Connector 500 Electronic equipment 501 Enclosure 503 Battery 504 First printed circuit board 505 Second printed circuit board 514, 515 Connector 600 Musical instrument 610 Soundboard 611 Support plate 620 Bridge 630 Sound source 640 Sound hole d1, d2, d3, d4, d5, d6 Thickness D11, D12, D14, D13, D21, D22, D23, D31, D32, D33 Direction (first direction)

Claims

1. A multilayer sheet comprising a first liquid crystal polymer sheet, a second liquid crystal polymer sheet, and a third liquid crystal polymer sheet, wherein the second liquid crystal polymer sheet contains a liquid crystal polymer as a material and is oriented in a first direction perpendicular to the thickness direction of the multilayer sheet, each of the first liquid crystal polymer sheet and the third liquid crystal polymer sheet contains a liquid crystal polymer as a material and has a lower degree of orientation than the second liquid crystal polymer sheet, and in the thickness direction of the multilayer sheet, the second liquid crystal polymer sheet is in contact with and sandwiched between the first liquid crystal polymer sheet and the third liquid crystal polymer sheet.

2. The multilayer sheet according to claim 1, wherein the thickness of the second liquid crystal polymer sheet is 1 / 2 or more and 100 times or less the thickness of the first liquid crystal polymer sheet.

3. A multilayer substrate comprising: a multilayer sheet according to claim 1 or 2; and a conductive layer disposed on the main surface of the multilayer sheet.

4. A multilayer substrate comprising: a multilayer sheet according to claim 1 or 2; and a signal line disposed on the main surface or inside the multilayer sheet.

5. The multilayer substrate according to claim 4, wherein the longitudinal direction of the signal line is parallel to the first direction.

6. The multilayer substrate according to claim 4, wherein the longitudinal direction of the signal line is aligned in a direction perpendicular to the first direction and the thickness direction of the multilayer sheet.

7. An electronic device comprising a multilayer substrate according to any one of claims 4 to 6, and a signal processing circuit connected to the signal line.

8. A soundboard comprising a support plate and a multilayer sheet according to claim 1 or 2, disposed on the support plate.

9. A musical instrument comprising a soundboard as described in claim 8 and a sound source, wherein sound emitted from the sound source propagates in the first direction.

Images