EP4645350A1

EP4645350A1 - Variable resistor and method for manufacturing variable resistor

Info

Publication number: EP4645350A1
Application number: EP23911275.8A
Authority: EP
Inventors: Masami Watanabe
Original assignee: Fujikura Ltd
Current assignee: Fujikura Ltd
Priority date: 2022-12-28
Filing date: 2023-08-31
Publication date: 2025-11-05
Also published as: CN120345041A; JPWO2024142491A1; TW202431287A; WO2024142491A1; TWI897032B

Abstract

A variable resistor 1A includes a base 11, a plurality of comb-like-pattern members 45a to 45j supported by the base 11 and extending with intervals therebetween, and a first resist layer 20 disposed on the base 11 such that spaces between the comb-like-pattern members 45a to 45j are filled with the first resist layer 20. The comb-like-pattern members 45a to 45j include upper surfaces 46 on a side opposite to the base 11, and the upper surfaces 46 are exposed through the first resist layer 20.

Description

[TECHNICAL FIELD]

The present invention relates to a variable resistor and a method for manufacturing the variable resistor.
For designated countries that are permitted to be incorporated by reference in the literature, the contents of Japanese Patent Application No. 2022-211822 filed with Japan Patent Office on December 28, 2022 is incorporated herein by reference and is regarded as a part of the description of this specification.

[BACKGROUND ART]

A variable resistor disclosed in Patent Document 1 includes a resistor disposed on an upper surface of a lower membrane substrate, a plurality of comb-like-pattern members connected to the resistor and arranged with intervals therebetween, and a connector disposed on a lower surface of an upper membrane substrate. Pressing of a slider bends the upper membrane substrate and the connector downward, thus bringing the connector into contact with adjacent comb-like-pattern members of the comb-like-pattern members (e.g., see Patent Document 1 (paragraph [0090] and Figure 8 to Figure 12)). The slider sliding on the upper membrane substrate while pressing the upper membrane substrate sequentially changes the comb-like-pattern members electrically connected to the connector, thus causing the resistive length (resistance value) of the resistor to change (e.g., see Patent Document 1 (paragraph [0092] and Figure 9)).

[CITATION LIST]

[PATENT DOCUMENT]

PATENT DOCUMENT 1: WO2021/205899

[SUMMARY OF THE INVENTION]

[PROBLEMS TO SOLVED BY INVENTION]

In the related art described above, there are spaces between the comb-like-pattern members, and when the slider slides on the upper membrane substrate while pressing the upper membrane substrate, the connector entering one of the spaces comes into contact with one of the comb-like-pattern members from a lateral side thereof. As a result, if the sliding described above is repeated, the comb-like-pattern members may be shaved by repetitive contact of the connector with the comb-like-pattern members from lateral sides thereof or may be brought down by a crosswise force to be separated from the lower membrane substrate. In such a case, the repeated sliding causes the degradation of the comb-like-pattern members.
A problem to be solved by the present invention is to provide a variable resistor capable of achieving a reduction or prevention of the degradation of comb-like-pattern members and to provide a method for manufacturing the variable resistor.

[MEANS FOR SOLVING PROBLEM]

[1] An aspect 1 of the present invention is a variable resistor including: a first base; a comb-like-pattern members supported by the first base and extending with intervals therebetween; and an insulator disposed on the first base such that spaces between the comb-like-pattern members are filled with the insulator, wherein the comb-like-pattern members include top edge surfaces on a side opposite to the first base, and the top edge surface is exposed through the insulator.
[2] An aspect 2 of the present invention may be the variable resistor according to the aspect 1, wherein the insulator includes a first main surface on the side opposite to the first base, and a height of the top edge surface from the first base is substantially identical to a height of the first main surface from the first base.
[3] An aspect 3 of the present invention may be the variable resistor according to the aspect 1 or the aspect 2, wherein the insulator includes a first main surface on the side opposite to the first base, and the first main surface extends substantially parallel to the first base.
[4] An aspect 4 of the present invention may be the variable resistor according to any one of the aspects 1 to 3, wherein the insulator includes: a first interposer interposed between the comb-like-pattern members; and a second interposer interposed between the first base and the comb-like-pattern members.
[5] An aspect 5 of the present invention may be the variable resistor according to any one of the aspects 1 to 4, wherein the insulator includes a first main surface on the side opposite to the first base, the variable resistor includes a resistor, the comb-like-pattern members include a first comb-like-pattern members connected to the resistor, the first comb-like-pattern members each include: a first portion in which the top edge surface is exposed through the insulator; and a second portion formed integrally with the first portion and connected to the resistor, and a thickness of the second portion is smaller than a thickness of the first portion in a first direction perpendicular to the first main surface.
[6] An aspect 6 of the present invention may be the variable resistor according to any one of the aspects 1 to 5, wherein the variable resistor includes: a resistor disposed on the first base; a first wiring pattern disposed on the first base and connected to the resistor; a spacer including an opening; a second base stacked on the first base with the spacer interposed therebetween; a connector disposed on the second base such that the connector is located in the opening, the connector being configured to be electrically connected to the resistor by pressing of a slider from an outside of the second base; and a second wiring pattern disposed on the second base and connected to the connector, or disposed on the first base and configured to be electrically connected to the connector by the pressing of the slider, the connector includes a non-overlapping area where the connector does not overlap the resistor in plan view, a slidable area where the slider is slidable is included in the non-overlapping area in plan view, the top edge surface is a surface of each of the comb-like-pattern members, the surface facing the connector, and a resistance value between the first wiring pattern and the second wiring pattern changes in accordance with a position of the slider.
[7] An aspect 7 of the present invention may be the variable resistor according to the aspect 6, wherein the second wiring pattern is disposed on the second base and connected to the connector, the comb-like-pattern members include a first comb-like-pattern members connected to the resistor, the first comb-like-pattern members overlap the slidable area in plan view, and the connector is brought into contact with the first comb-like-pattern members by the pressing of the slider from the outside of the second base.
[8] An aspect 8 of the present invention may be the variable resistor according to the aspect 6, wherein the second wiring pattern is disposed on the first base, the plurality of comb-like-pattern members include first comb-like-pattern members connected to the resistor, the first comb-like-pattern members and the second wiring pattern overlapping the slidable area in plan view, and the connector is brought into contact with the first comb-like-pattern members and the second wiring pattern by the pressing of the slider from the outside of the second base.
[9] An aspect 9 of the present invention may be the variable resistor according to the aspect 6, wherein the second wiring pattern is disposed on the first base, the comb-like-pattern members include: first comb-like-pattern members connected to the resistor; and second comb-like-pattern members connected to the second wiring pattern, the first and second comb-like-pattern members overlap the slidable area in plan view, the first comb-like-pattern members and the second comb-like-pattern members are alternately arranged in the slidable area along a direction in which the connector extends, and the connector is brought into contact with the first comb-like-pattern members and the second comb-like-pattern members by the pressing of the slider from the first base.
[10] An aspect 10 of the present invention may be the variable resistor according to any one of the aspects 6 to 9, wherein the variable resistor further includes a third wiring pattern disposed on the first base and connected to the resistor, the comb-like-pattern members include: a third comb-like-pattern member connected to the first wiring pattern; and a fourth comb-like-pattern member connected to the third wiring pattern, and the third and fourth comb-like-pattern members overlap the slidable area in plan view.
[11] An aspect 11 of the present invention is a method for manufacturing the variable resistor according to any one of the aspects 1 to 10, the method including: a first step of preparing a support including a release-treated surface; a second step of forming the comb-like-pattern members on the release-treated surface of the support; a third step of forming the insulator on the release-treated surface such that spaces between the comb-like-pattern members are filled with the insulator; and a fourth step of transferring the comb-like-pattern members and the insulator from the support to the first base.

[EFFECT OF THE INVENTION]

According to the present invention, it is possible to achieve a reduction or prevention of the degradation of the comb-like-pattern members by filling the spaces between the comb-like-pattern members with the insulator and exposing a top edge surface of each of the comb-like-pattern members on a side opposite to the first base through the insulator.

[BRIEF DESCRIPTION OF DRAWING(S)]

FIG. 1 is a plan view illustrating a variable resistor in a first embodiment of the present invention;
FIG. 2 is a sectional view taken along the line II-II in FIG. 1;
FIG. 3 is a sectional view taken along the line III-III in FIG. 1;
FIG. 4 is a sectional view taken along the line IV-IV in FIG. 1;
FIG. 5 is a sectional view taken along the line V-V in FIG. 1;
FIG. 6 is a plan view illustrating a lower membrane substrate of the variable resistor in the first embodiment of the present invention;
FIG. 7 is a bottom view illustrating a spacer and an upper membrane substrate of the variable resistor in the first embodiment of the present invention;
FIG. 8(A) to FIG. 8(D) are sectional views illustrating an example of a method for manufacturing the variable resistor in the first embodiment of the present invention;
FIG. 9(A) to FIG. 9(D) are sectional views illustrating an example of the method for manufacturing the variable resistor in the first embodiment of the present invention;
FIG. 10 is a plan view illustrating a variable resistor in a second embodiment of the present invention;
FIG. 11 is a sectional view taken along the line XI-XI in FIG. 10;
FIG. 12 is a plan view illustrating a lower membrane substrate of the variable resistor in the second embodiment of the present invention;
FIG. 13 is a bottom view illustrating a spacer and an upper membrane substrate of the variable resistor in the second embodiment of the present invention;
FIG. 14 is a plan view illustrating a variable resistor in a third embodiment of the present invention;
FIG. 15 is a sectional view taken along the line XV-XV in FIG. 14; and
FIG. 16 is a plan view illustrating a lower membrane substrate of the variable resistor in the third embodiment of the present invention.

[MODE(S) FOR CARRYING OUT THE INVENTION]

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<<First Embodiment>>

FIG. 1 is a plan view illustrating a variable resistor 1A in a first embodiment, FIG. 2 is a sectional view taken along the line II-II in FIG. 1, FIG. 3 is a sectional view taken along the line III-III in FIG. 1, FIG. 4 is a sectional view taken along the line IV-IV in FIG. 1, and FIG. 5 is a sectional view taken along the line V-V in FIG. 1. FIG. 6 is a plan view illustrating a lower membrane substrate 10A of the variable resistor 1A in the first embodiment, and FIG. 7 is a bottom view illustrating a spacer 90 and an upper membrane substrate 60A of the variable resistor 1A in the first embodiment.
As illustrated in FIG. 1 to FIG. 7, the variable resistor 1A in the present embodiment includes the lower membrane substrate 10A (see FIG. 2 to FIG. 6), the upper membrane substrate 60A (see FIG. 2 to FIG. 5 and FIG. 7), the spacer 90, and a slider 100.
The lower membrane substrate 10A includes a resistor 40, a plurality of (10 in this example) comb-like-pattern members 45a to 45j and wiring patterns 31 and 35. Note that, in the present embodiment, the plurality of comb-like-pattern members 45a to 45j may be collectively referred to as "comb-like-pattern members 45."
The upper membrane substrate 60A includes a connector 80 that electrically connects the resistor 40 and a wiring pattern 70. These membrane substrates 10A and 60A are stacked with the spacer 90 interposed therebetween. The spacer 90 keeps a gap between the membrane substrates 10A and 60A. The slider 100 is configured to slide on the upper membrane substrate 60A in a slidable area SA (see FIG. 1) while pressing the upper membrane substrate 60A. The pressing of the slider 100 electrically connects the resistor 40 and the wiring pattern 70 via the connector 80 and the comb-like-pattern members 45.
In this variable resistor 1A, the slider 100 that slides on the upper membrane substrate 60A while pressing the upper membrane substrate 60A sequentially changes one of the comb-like-pattern members 45 to be brought into contact with the connector 80. This changes the position of an electrical connection between the connector 80 and the resistor 40, thus enabling the resistive length (resistance value) of the resistor 40 to be changed. Examples of the application of such a variable resistor 1A can include a variable resistive element, a position sensor, a switch, and an encoder. Note that the application of the variable resistor 1A in the present embodiment is not particularly limited to the above.
A configuration of the variable resistor 1A in the present embodiment will be described in detail below.
As illustrated in FIG. 6, the lower membrane substrate 10A is a wiring board including a base 11, a first resist layer 20, the wiring patterns 31 and 35, the resistor 40, the comb-like-pattern members 45, and a second resist layer 50. Note that the base 11 in the present embodiment corresponds to an example of a "first base" in the present invention, the first resist layer 20 in the present embodiment corresponds to an example of an "insulator" in the present invention, the comb-like-pattern members 45a to 45j in the present embodiment correspond to an example of "comb-like-pattern members," the comb-like-pattern member 45a in the present embodiment corresponds to an example of a "third comb-like-pattern member" in the present invention, the comb-like-pattern members 45b to 45i in the present embodiment correspond to an example of "first comb-like-pattern members," and the comb-like-pattern member 45j in the present embodiment corresponds to an example of a "fourth comb-like-pattern member" in the present invention. In addition, the wiring pattern 31 in the present embodiment corresponds to an example of a "first wiring pattern" in the present invention, and the wiring pattern 35 in the present embodiment corresponds to an example of a "third wiring pattern" in the present invention.
The base 11 is a film-like member constituted by a flexible, electrically insulating material. Examples of the material constituting the base 11 can include a resin material. More specifically, examples of the material can include polyethylene terephthalate (PET) and polyethylene naphthalate (PEN). More specifically, for example, an adhesive tape in which a PET film includes an adhesive layer on one of its main surfaces can be used as the base 11. Alternatively, hot melt or the like may be used as the adhesive layer. Note that the base 11 need not be flexible.
The first resist layer 20 is provided on an upper surface 12 of the base 11. The first resist layer 20 is formed by solidifying (curing) an electrically insulating resist material. Specific examples of the resist material can include resin materials such as epoxy resin, urethane resin, polyester resin, and acrylic resin.
As illustrated in FIG. 2 and FIG. 6, the first resist layer 20 includes a reduced-thickness portion 21 and a protruding portion 22. As illustrated in FIG. 6, the reduced-thickness portion 21 surrounds the protruding portion 22 and is thin relative to the protruding portion 22.
The reduced-thickness portion 21 is overlaid with the second resist layer 50 in plan view (as viewed from above or below (in the normal direction of the main surface of the variable resistor 1A (Z directions in the drawing) the variable resistor 1A). The reduced-thickness portion 21 is not exposed through the second resist layer 50. As illustrated in FIG. 3, the reduced-thickness portion 21 includes portions that are not directly covered with the second resist layer 50 but indirectly covered with the second resist layer 50 via the wiring patterns 31 and 35, the resistor 40, and the comb-like-pattern members 45.
In contrast, as illustrated in FIG. 2 and FIG. 6, the protruding portion 22 in the present embodiment is surrounded by the reduced-thickness portion 21. The protruding portion 22 is not overlaid with the second resist layer 50 in plan view. The protruding portion 22 is exposed through the second resist layer 50. As illustrated in FIG. 2, the thickness of the protruding portion 22 is large relative to the thickness of the reduced-thickness portion 21. An upper surface 22a of the protruding portion 22 protrudes upward (in the +Z direction in the drawing) from an upper surface 21a of the reduced-thickness portion 21. Thus, with the protruding portion 22, an opening 51 of the second resist layer 50 is filled. Note that the upper surface 22a of the protruding portion 22 in the present embodiment corresponds to an example of a "first main surface" in the present invention.
The upper surface 22a of the protruding portion 22 is substantially parallel to the upper surface 12 of the base 11. A height H₁ of the upper surface 22a from the base 11 is substantially the same as a height H₂ of an upper surface 50a of the second resist layer 50 from the base 11 (H₁ = H₂), and thus the upper surfaces 22a and 50a are substantially flush with each other.
As illustrated in FIG. 2, FIG. 3, and FIG. 6, the comb-like-pattern members 45 are embedded from the reduced-thickness portion 21 to the protruding portion 22 of the first resist layer 20. The first resist layer 20 further includes, around the comb-like-pattern members 45, a plurality of (9 in this example) first interposers 23, a plurality of (10 in this example) second interposers 24, and a plurality of (2 in this example) third interposers 25. As illustrated in FIG. 2, in the first resist layer 20 in the present embodiment, the plurality of first interposers 23 and the plurality of second interposers 24 are alternately arranged along an X direction between the third interposers 25 and 25. Note that the numbers of the first and second interposers 23 and 24 are not limited to particular numbers and change in accordance with the number of the comb-like-pattern members 45.
As illustrated in FIG. 6, the first interposers 23 are located between the comb-like-pattern members 45 such that spaces between the comb-like-pattern members 45 are filled with the first interposers 23. The first interposers 23 extend from the reduced-thickness portion 21 to the protruding portion 22 of the first resist layer 20 along a direction in which the comb-like-pattern members 45 extend (a Y direction in the drawing).
As illustrated in FIG. 5, the first interposers 23 each include a first exposed portion 23a, a first unexposed portion 23b, and a second unexposed portion 23c. The first exposed portion 23a and the first and second unexposed portions 23b and 23c are integrally formed with one another.
The first exposed portion 23a constitutes a portion of the protruding portion 22 and is exposed through the second resist layer 50. In the first exposed portion 23a, the upper surface 22a of the protruding portion 22 is substantially flush with the upper surface 50a of the second resist layer 50. In addition, in the first exposed portion 23a, a surface roughness Ra of the upper surface 22a of the protruding portion 22 can be set to, for example, 0.01 µm to 0.1 µm.
The first and second unexposed portions 23b and 23c constitute portions of the reduced-thickness portion 21. The first unexposed portion 23b is located between the first exposed portion 23a and the resistor 40. In the first unexposed portion 23b, the upper surface 21a of the reduced-thickness portion 21 is covered with the second resist layer 50. As a result, the first unexposed portion 23b is interposed between the second resist layer 50 and the base 11.
The first unexposed portion 23b is connected to the second unexposed portion 23c. In the second unexposed portion 23c, the upper surface 21a of the reduced-thickness portion 21 is covered with the resistor 40. As a result, the second unexposed portion 23c is interposed between the resistor 40 and the base 11.
In the present embodiment, a thickness T₁ of the first exposed portion 23a is larger than a thickness T₂ of the first unexposed portion 23b, and the thickness T₂ of the first unexposed portion 23b is larger than a thickness T₃ of the second unexposed portion 23c (T₁ > T₂ > T₃). Therefore, in each of the first interposers 23 in the present embodiment, a step is formed between the first exposed portion 23a and the first unexposed portion 23b, and a step is also formed between the first unexposed portion 23b and the second unexposed portion 23c. As a result, the first interposers 23 each have a thickness that decreases stepwise as the first interposer extends toward the ends of the comb-like-pattern members 45 closer to the resistor 40 (extends in the -Y direction in the drawing). Note that the thicknesses in the present embodiment are thicknesses in a direction perpendicular to the upper surface 12 of the base 11 (a Z direction in the drawing). The Z direction in the present embodiment corresponds to an example of a "first direction" in the present invention.
As illustrated in FIG. 2 and FIG. 3, the second interposers 24 are located between lower surfaces 47 of the comb-like-pattern members 45 and the upper surface 12 of the base 11. The second interposers 24 in the present embodiment are each located between two first interposers 23 and 23. The second interposers 24 each have a rectangular-parallelepiped shape that has the same width as the comb-like-pattern members 45.
The second interposers 24 located between the comb-like-pattern members 45 and the base 11 in this manner can improve the adhesive power of the comb-like-pattern members 45 to the base 11. Thus, it is possible to achieve a reduction or prevention of the degradation of the comb-like-pattern members 45. In addition, the second interposers 24 are also capable of reducing or preventing the penetration of steam and the like from the base 11 side. Thus, it is possible to achieve a reduction or prevention of the degradation of the comb-like-pattern members 45.
As illustrated in FIG. 2, the third interposers 25 are located between the second resist layer 50, and the comb-like-pattern members 45a and 45j. The third interposers 25 also constitute portions of the protruding portion 22 and are exposed through the second resist layer 50. The upper surfaces of the third interposers 25 are included in the upper surface 22a of the protruding portion 22 and are substantially flush with the upper surface 50a of the second resist layer 50. In addition, in the third interposers 25, a surface roughness Ra of the upper surface 22a of the protruding portion 22 can be set to, for example, 0.01 µm to 0.1 µm.
As illustrated in FIG. 3, the wiring patterns 31 and 35 are provided on the reduced-thickness portion 21 of the first resist layer 20. The wiring patterns 31 and 35 are formed by solidifying (curing) a conductive paste. The conductive paste is made by mixing a conductive particle and a binder resin into water or a solvent, and various additives. The conductive paste constituting the wiring patterns 31 and 35 is a low-resistance conductive paste that has a relatively low electrical resistance value. Note that the method of forming the wiring patterns 31 and 35 is not particularly limited to the above method.
Specific examples of the conductive particle can include silver, copper, nickel, tin, bismuth, zinc, indium, and palladium, and alloys thereof. Specific examples of the binder resin can include acrylic resin, polyester resin, epoxy resin, vinyl resin, urethane resin, phenolic resin, polyimide resin, silicone resin, and fluororesin. Examples of the solvent included in the conductive paste can include α-terpineol, butyl carbitol acetate, butyl carbitol, 1-decanol, butyl cellosolve, diethylene glycol monoethyl ether acetate, and tetradecane.
Although not particularly limited to, a silver paste that contains silver as the main component of the conductive particle or a copper paste that contains copper as the main component of the conductive particle is used as the low-resistance conductive paste in the present embodiment. Note that, as the conductive particle contained in the conductive paste, a metal salt may be used. The metal salt can include salts of the metals mentioned above. The binder resin may be omitted from the conductive paste. Instead of the conductive paste, a conductive ink may be used.
As illustrated in FIG. 6, the wiring patterns 31 and 35 in the present embodiment are connected to both ends of the resistor 40. In the present embodiment, the wiring patterns 31 and 35 extend in an X direction in the drawing, which is substantially parallel to the resistor 40. However, this is not limiting. The wiring patterns 31 and 35 may extend in a direction other than the X direction, such as the Y direction.
As illustrated in FIG. 3 and FIG. 6, the resistor 40 is provided between the wiring patterns 31 and 35 and extends along the X direction in the drawing. The resistor 40 is also formed by solidifying (curing) a conductive paste, as with the wiring patterns 31 and 35 mentioned above.
The conductive paste constituting the resistor 40 is a high-resistance conductive paste that has a high electrical resistance value compared with the low-resistance conductive paste mentioned above. The conductive paste constituting the resistor 40 contains a conductive particle having a higher electric resistivity than the conductive particle of the conductive paste constituting the wiring patterns 31 and 35 mentioned above. That is, the resistor 40 is constituted by a material having a higher electric resistivity than the material constituting the wiring patterns 31 and 35. The resistance value of the resistor 40 is sufficiently higher than the resistance values of the wiring patterns 31 and 35 such that the resistance values of the wiring patterns 31 and 35 can be considered to be negligible. Specifically, the resistance value of the resistor 40 is at least 10 times the resistance values of the wiring patterns 31 and 35 and is preferably at least 100 times the resistance values of the wiring patterns 31 and 35. The electric resistivity of the material constituting the resistor 40 is at least 10 times the electric resistivity of the material constituting the wiring patterns 31 and 35 and is preferably at least 100 times the electric resistivity of the material constituting the wiring patterns 31 and 35.
Specific examples of such a high-resistance conductive paste can include a carbon paste. Specific examples of the conductive particle contained in the conductive paste constituting the resistor 40 can include carbon-based materials such as graphites, carbon blacks (furnace black, acetylene black, Ketjenblack), carbon nanotubes, and carbon nanofibers.
As mentioned above, the resistor 40 covers an end of the wiring pattern 31, which is one of the wiring patterns, and covers an end of the wiring pattern 35, which is the other. The resistor 40 connects the wiring patterns 31 and 35. Although not particularly illustrated, the wiring pattern 31 being the one of the wiring patterns is connected to a power supply, while the wiring pattern 35 being the other is connected to the ground.
The comb-like-pattern members 45a to 45j are formed by curing a low-resistance conductive paste, as with the wiring patterns 31 and 35. That is, the comb-like-pattern members 45a to 45j are constituted by a material that has a lower electric resistivity than the material constituting the resistor 40. The resistance value of the resistor 40 is sufficiently higher than those of the comb-like-pattern members 45a to 45j such that the resistance values of the comb-like-pattern members 45a to 45j can be considered to be negligible. Specifically, the resistance value of the resistor 40 is at least 10 times those of the comb-like-pattern members 45a to 45j and is preferably at least 100 times those of the comb-like-pattern members 45a to 45j. The electric resistivity of the material constituting the resistor 40 is at least 10 times the electric resistivity of the material constituting the comb-like-pattern members 45a to 45j and is preferably at least 100 times the electric resistivity of the material constituting the comb-like-pattern members 45a to 45j.
As illustrated in FIG. 6, the comb-like-pattern member 45a, which is the leftmost comb-like-pattern member in the drawing, branches off from the wiring pattern 31 and protrudes along the Y direction in the drawing. That is, the comb-like-pattern member 45a is connected to the wiring pattern 31 and extends to below the slidable area SA (see FIG. 1). Likewise, the comb-like-pattern member 45j, which is the rightmost comb-like-pattern member in the drawing, branches off from the wiring pattern 35 and protrudes along the Y direction in the drawing. That is, the comb-like-pattern member 45j is connected to the wiring pattern 35 and extends to below the slidable area SA (see FIG. 1).
In contrast, as illustrated in FIG. 3, eight comb-like-pattern members 45b to 45i, which are located between the leftmost and rightmost comb-like-pattern members 45a and 45j, are electrically connected to the resistor 40 with ends of the comb-like-pattern members 45b to 45i being embedded below the resistor 40. As illustrated in FIG. 6, the comb-like-pattern members 45b to 45i protrude from the resistor 40 in the +Y direction. That is, the comb-like-pattern members 45b to 45i are connected to the wiring pattern 40 and extend to below the slidable area SA (see FIG. 1). Note that the leftmost and rightmost comb-like-pattern members 45a and 45j may be embedded below the resistor 40 rather than branching off from the wiring patterns 31 and 35, respectively, as with the comb-like-pattern members 45b to 45i.
All of the comb-like-pattern members 45a to 45j extend along the Y direction in the drawing. The planar shape of the comb-like-pattern members 45a to 45j is linear. The plurality of comb-like-pattern members 45a to 45j are arranged substantially parallel to one another. In addition, the plurality of comb-like-pattern members 45a to 45j are disposed at substantially regular intervals. Note that the number of the comb-like-pattern members 45 is not particularly limited to the above number. In this regard, the more the number of the comb-like-pattern members 45, the more the resolution of the output of the variable resistor 1A can be increased, as will be described later. In addition, the intervals between the comb-like-pattern members 45a to 45j are not limited to regular intervals as long as the intervals are provided between the comb-like-pattern members 45a to 45j.
As illustrated in FIG. 4, the comb-like-pattern members 45b to 45i each include a second exposed portion 48a, a third unexposed portion 48b, and a fourth unexposed portion 48c. The second exposed portion 48a and the third and fourth unexposed portions 48b and 48c are integrally formed with one another. The second exposed portion 48a in the present embodiment corresponds to an example of a "first portion" in the present invention, and the fourth unexposed portion 48c in the present embodiment corresponds to an example of a "second portion" in the present invention.
The second exposed portion 48a is located between the first interposers 23. In the second exposed portion 48a, an upper surface 46 of each of the comb-like-pattern members 45b to 45i is exposed between the first interposers 23 of the first resist layer 20. The upper surface 46 is not covered with the second resist layer 50, either. Note that the upper surface 46 in the present embodiment corresponds to an example of a "top edge surface" in the present invention.
In the present embodiment, a height H₃ from the base 11 to the upper surface 46 is substantially the same as heights H₁ and H₂ of the upper surfaces 22a and 50a described above (H₁ = H₂ = H₃). That is, the upper surfaces 46, 22a, and 50a are substantially flush with one another. In addition, in the second exposed portion 48a, a surface roughness Ra of the upper surface 46 of the comb-like-pattern members 45b to 45i can be set to, for example, 0.01 µm to 0.1 µm.
In the present embodiment, the upper surface 46 is substantially parallel to the upper surface 12 of the base 11. Therefore, the upper surface 46 is also substantially parallel to the upper surface 22a and the upper surface 50a.
Between the second exposed portion 48a and the resistor 40, the third unexposed portion 48b is located. In the third unexposed portion 48b, the upper surface 46 is covered with the second resist layer 50. As a result, the third unexposed portion 48b is interposed between the second resist layer 50 and the corresponding second interposer 24 of the first resist layer 20.
Between the third unexposed portion 48b and the resistor 40, the fourth unexposed portion 48c is located. In the fourth unexposed portion 48c, the upper surface 46 is covered with the resistor 40. As a result, the fourth unexposed portion 48c is interposed between the resistor 40 and the corresponding second interposer 24 of the first resist layer 20.
In the present embodiment, a thickness T₄ of the second exposed portion 48a is larger than a thickness T₅ of the third unexposed portion 48b, and the thickness T₅ of the third unexposed portion 48b is larger than a thickness T₆ of the fourth unexposed portion 48c (T₄ > T₅ > T₆). Therefore, in each of the comb-like-pattern members 45b to 45i in the present embodiment, a step is formed between the second exposed portion 48a and the third unexposed portion 48b, and a step is also formed between the third unexposed portion 48b and the fourth unexposed portion 48c. As a result, the comb-like-pattern members 45b to 45i each have a thickness that decreases stepwise as the comb-like-pattern member extends in the -Y direction in the drawing.
In contrast, the comb-like-pattern members 45a and 45j, which are the leftmost and rightmost comb-like-pattern members of the comb-like-pattern members 45, have a sectional shape that is slightly different from a sectional shape of the comb-like-pattern members 45b to 45i. Although not particularly illustrated, the resistor 40 is not interposed between the comb-like-pattern members 45a and 45j and the second resist layer 50. Thus, in the comb-like-pattern members 45a and 45j, the fourth unexposed portion 48c is absent, and the third unexposed portion 48b extends from the second exposed portion 48a to the wiring patterns 31 and 35, respectively.
The second resist layer 50 is formed by solidifying (curing) a resist material, as with the first resist layer 20. Examples of the resist material can include resin materials such as epoxy resin, urethane resin, polyester resin, and acrylic resin.
As illustrated in FIG. 2 to FIG. 4, the second resist layer 50 covers the reduced-thickness portion 21 of the first resist layer 20, the wiring patterns 31 and 35, the resistor 40, and the third unexposed portion 48b of each of the comb-like-pattern members 45. The second resist layer 50 has the opening 51 and surrounds the protruding portion 22 of the first resist layer 20.
As illustrated in FIG. 7, the upper membrane substrate 60A is a wiring board including a base 61, the wiring pattern 70, and the connector 80. The base 61 in the present embodiment corresponds to an example of a "second base" in the present invention, and the wiring pattern 70 in the present embodiment corresponds to an example of a "second wiring pattern" in the present invention.
The base 61 is a film-like member constituted by a flexible, electrically insulating material, as with the base 11 mentioned above. Examples of the material constituting the base 11 can include a resin material. More specifically, examples of the material can include polyethylene terephthalate (PET) and polyethylene naphthalate (PEN). Note that the material constituting the base 61 is not particularly limited to the material described above. The base 61 may be constituted by a plate made of a conductive material such as a metal material. In this case, the base 61 may also perform the function of the connector 80. In addition, the base 61 may also perform the function of the wiring pattern 70. Note that even in the case where the base 61 is constituted by a conductive plate, the connector 80 and the wiring pattern 70 may be formed on the base 61, separately from the base 61.
The wiring pattern 70 is formed by printing a low-resistance conductive paste on a lower surface 62 of the base 61 and curing the low-resistance conductive paste. That is, the wiring pattern 70 is constituted by a material having a lower electric resistivity than the material constituting the resistor 40. The resistance value of the resistor 40 is sufficiently higher than the resistance value of the wiring pattern 70 such that the resistance value of the wiring pattern 70 can be considered to be negligible. Specifically, the resistance value of the resistor 40 is at least 10 times the resistance value of the wiring pattern 70 and is preferably at least 100 times the resistance value of the wiring pattern 70. The electric resistivity of the material constituting the resistor 40 is at least 10 times the electric resistivity of the material constituting the wiring pattern 70 and is preferably at least 100 times the electric resistivity of the material constituting the wiring pattern 70. Note that the method of forming the wiring pattern 70 is not particularly limited to the above method.
The wiring pattern 70 is directly connected to the connector 80. The connector 80 includes a first body 81 and a first protective layer 82. Note that the connector 80 need not include the first protective layer 82.
The first body 81 is provided on the lower surface 62 of the base 61. The first body 81 is formed by printing and curing a low-resistance conductive paste, as with the wiring patterns 31 and 35 mentioned above. That is, the first body 81 is constituted by a material having a lower electric resistivity than the material constituting the resistor 40. The resistance value of the resistor 40 is sufficiently higher than the resistance value of the first body 81 such that the resistance value of the first body 81 can be considered to be negligible. Specifically, the resistance value of the resistor 40 is at least 10 times the resistance value of the first body 81 and is preferably at least 100 times the resistance value of the first body 81. The electric resistivity of the material constituting the resistor 40 is at least 10 times the electric resistivity of the material constituting the first body 81 and is preferably at least 100 times the electric resistivity of the material constituting the first body 81.
In contrast, the first protective layer 82 is a layer that protects the first body 81. The first protective layer 82 is formed by printing and curing a high-resistance conductive paste. The first protective layer 82 is provided on the lower surface 62 of the base 61 such that the first protective layer 82 covers the entire first body 81.
As illustrated in FIG. 1, the connector 80 is provided on the lower surface 62 of the base 61 such that the connector 80 overlaps the comb-like-pattern members 45 of the lower membrane substrate 10A in plan view.
The spacer 90 is a film-like member constituted by a flexible, electrically insulating material, as with the bases 11 and 61 mentioned above. Examples of the material constituting the spacer 90 can include a resin material. More specifically, examples of the material can include polyethylene terephthalate (PET) and polyethylene naphthalate (PEN).
As illustrated in FIG. 1 to FIG. 5 and FIG. 7, the spacer 90 has an opening 91 with a rectangular, planar shape. The opening 91 is larger than the connector 80 and has a size large enough to include the connector 80. In the present embodiment, the opening 91 has a size large enough to include not only the connector 80 but also the comb-like-pattern members 45. The opening 91 is formed in the spacer 90 such that the opening 91 includes the connector 80 and the comb-like-pattern members 45 in the state where the membrane substrates 10A and 60A are stacked with the spacer 90 interposed therebetween. Note that it suffices that at least a portion of the connector 80 is located in the opening 91 of the spacer 90. A portion of the connector 80 may extend to the outside of the opening 91 to be interposed between the spacer 90 and the base 61.
As mentioned above, the membrane substrates 10A and 60A are stacked with the spacer 90 interposed therebetween. At this time, as illustrated in FIG. 2 to FIG. 5, the membrane substrates 10A and 60A are stacked such that the lower surface 62 of the base 61 of the upper membrane substrate 60A faces the upper surface 12 of the base 11 of the lower membrane substrate 10A. The base 11 of the lower membrane substrate 10A and the spacer 90 are bonded together with a bonding layer (not illustrated) interposed therebetween, and the spacer 90 and the base 61 of the upper membrane substrate 60A are also bonded together with a bonding layer (not illustrated) interposed therebetween.
As illustrated in FIG. 1, the connector 80 and the comb-like-pattern members 45 are included in the opening 91 in plan view. As illustrated in FIG. 4, the connector 80 faces the comb-like-pattern members 45 in sectional view. As illustrated in FIG. 1, the connector 80 has a non-overlapping area NA, where the connector 80 does not overlap the resistor 40 in plan view, in the present embodiment.
As illustrated in FIG. 2, FIG. 4, and FIG. 5, the spacer 90 keeps a gap between the connector 80 and the comb-like-pattern members 45. As will be described later, the pressing of the slider 100 deforms the base 11 of the upper membrane substrate 60A, and the deformation brings the connector 80 into contact with one of the comb-like-pattern members 45 to electrically connect them.
Note that although the thickness of the spacer 90 is set in the present embodiment such that the connector 80 comes into contact with none of the comb-like-pattern members 45 where the slider 100 is not pressed, the thickness is not particularly limited to this. The thickness of the spacer 90 may be set such that the connector 80 is constantly in contact with one of the comb-like-pattern members 45.
Note that "electrically connecting" the connector and the resistor in the present invention refers to the state where the resistance value between the connector and one of the comb-like-pattern members is lower than or equal to a predetermined threshold value and does not refer to the state where the connector is simply in contact with one of the comb-like-pattern members while the slider 100 is not pressed as described above.
The slider 100 is a member that includes, at its tip, a presser 110 having a semi-cylindrical shape. The slider 100 is constituted by, for example, a metal material. Note that the configuration of the slider 100 is not particularly limited to the above as long as the configuration enables the slider 100 to slide while pressing an upper surface 63 of the base 61 of the upper membrane substrate 60A. In the present embodiment, the pressing target of the slider 100 is the upper surface 63 of the base 61 of the upper membrane substrate 60A. Thus, the slider 100 may be constituted by an electrically insulating material such as a resin material. Alternatively, instead of the slider 100, a finger of an operator may be used, as will be described later.
The slider 100 is slidably held by, for example, a housing (not illustrated) that houses the variable resistor 1A. In the state where the presser 110 is applied to the upper surface 63 of the base 61 of the upper membrane substrate 60A with a predetermined pressing force, the slider 100 is capable of reciprocating along the X direction in the drawing (a direction in which the connector 80 extends (longitudinal direction)) while the pressing force is kept constant. As illustrated in FIG. 1, in plan view, the slidable area SA, where the slider 100 is slidable, is included in the non-overlapping area NA of the connector 80 mentioned above and does not overlap the resistor 40 in the present embodiment. In addition, the whole area of the connector 80 corresponds to the non-overlapping area NA. The slider 100 is configured to be capable of reciprocating within the slidable area SA along the X direction in the drawing. The slidable area SA in the present embodiment corresponds to an example of a "slidable area" in the present invention.
As illustrated in FIG. 2, the pressing of the slider 100 bends the base 61 of the upper membrane substrate 60A downward, bringing the connector 80 into contact with one of the comb-like-pattern members 45. This electrically connects the resistor 40 and the wiring pattern 70 together via the connector 80. Specifically, in the state illustrated in FIG. 2, the comb-like-pattern member 45f of the comb-like-pattern members 45a to 45j and the connector 80 are electrically connected together.
Note that the number of the comb-like-pattern members 45a to 45j that are connected to the connector 80 at the same time by the pressing of the slider 100 may be more than one.
In the present embodiment, the slider 100 sliding on the upper membrane substrate 60A while pressing the upper membrane substrate 60A sequentially changes one of the comb-like-pattern members 45 connected by the connector 80, thus causing the resistive length (resistance value) of the resistor 40 to vary.
For example, in the state illustrated in FIG. 2, the comb-like-pattern member 45f is connected via the connector 80 as mentioned above. As the slider 100 slides in the +X direction in the drawing from this state, the one of the comb-like-pattern members 45 connected via the connector 80 is changed in the sequence such as comb-like-pattern member 45f -> comb-like-pattern member 45g -> comb-like-pattern member 45h -> comb-like-pattern member 45i -> comb-like-pattern member 45j.
With these changes, the wiring pattern 70 connected to the connector 80 detects a voltage (detected voltage) that changes as a function of the one of the comb-like-pattern members 45 connected via the connector 80. That is, the resistance value between the wiring patterns 31 and 70 changes in accordance with the position of the pressing of the slider 100. In the case where the slider 100 slides in the +X direction in the drawing, the resistance value between the wiring patterns 31 and 70 gradually increases with the sliding of the slider 100. To the wiring patterns 31 and 70 of the variable resistor 1A, a multimeter or the like is connected. The multimeter or the like outputs a potential difference between a power supply voltage and the detected voltage of the wiring pattern 70.
In contrast, in the case where the slider 100 slides in the -X direction in the drawing in the state illustrated in FIG. 2, the combination of the one of comb-like-pattern members connected via the connector 80 is changed with the sliding of the slider 100 in the sequence such as comb-like-pattern member 45f -> comb-like-pattern member 45e -> comb-like-pattern member 45d -> comb-like-pattern member 45c -> comb-like-pattern member 45b -> comb-like-pattern member 45a. In this case, the resistance value between the wiring patterns 31 and 70 gradually decreases with the sliding of the slider 100.
For example, in the case where the leftmost comb-like-pattern member 45a in FIG. 2 is electrically connected to the wiring pattern 70 via the connector 80, a voltage indicating substantially the same potential as the power supply voltage is detected by the wiring pattern 70, and the multimeter or the like outputs the potential difference between the power supply voltage and the detected voltage of the wiring pattern 70 (e.g., 0 [V]).
In contrast, in the case where the comb-like-pattern member 45f located substantially midway is electrically connected to the wiring pattern 70 via the connector 80, a voltage indicating a potential substantially half the potential indicated by the power supply voltage is detected by the wiring pattern 70, and the multimeter or the like outputs the potential difference between the power supply voltage and the detected voltage of the wiring pattern 70 (e.g., 2.5 [V]).
In the case where the rightmost comb-like-pattern member 45j in FIG. 2 is electrically connected to the wiring pattern 70 via the connector 80, a voltage indicating substantially the same potential as the ground is detected by the wiring pattern 70, and the multimeter or the like outputs the potential difference between the power supply voltage and the detected voltage of the wiring pattern 70 (e.g., 5 [V]).
As above, in the present embodiment, the resistance value between the wiring patterns 31 and 70 changes in accordance with the one of the comb-like-pattern members 45 connected via the connector 80. Thus, the output of the variable resistor 1A is stepwise. As a result, increasing the number of the comb-like-pattern members 45 to decrease the pitch of the comb-like-pattern members 45 can increase the resolution of the output of the variable resistor 1A.
As described above, in the present embodiment, the spaces between the comb-like-pattern members 45a to 45j are filled with the first interposers 23 of the first resist layer 20. Thus, it is possible to reduce the contact of the connector 80 with the lateral surfaces of the comb-like-pattern members 45a to 45j. Therefore, it is possible to prevent the comb-like-pattern members 45a to 45j from being shaved or prevent the comb-like-pattern members 45a to 45j from being brought down by crosswise force to be separated from the lower membrane substrate, thus achieving a reduction or prevention of the degradation of the comb-like-pattern members 45a to 45j.
In addition, the leftmost and rightmost comb-like-pattern members 45a and 45j of the comb-like-pattern members 45 can also be protected with the third interposers 25 in addition to the first interposers 23. Thus, it is possible to achieve a reduction or prevention of the degradation of the comb-like-pattern members 45a and 45j.
In the related art described above, differences arise between the amounts of bending of the upper membrane substrate and the connector when the connector is in contact with the upper surface of one of the comb-like-pattern members and the amounts of bending of the upper membrane substrate and the connector when the connector enters between a space between comb-like-pattern members. As a result, the slider moves in not only its sliding direction but also an up-down direction, which may make the conductive contact between the connector and one of the comb-like-pattern members unstable. In such a case, the problem of deterioration in the detection precision of the variable resistor (e.g., precision in the linearity of the output value from the variable resistor with respect to the position of the slider) also arises.
In contrast, in the present embodiment, the movement of the connector 80 in a downward direction (the -Z direction in the drawing) in a space between the comb-like-pattern members 45 when the slider 100 moves to a position corresponding to the space between the comb-like-pattern members 45 can be reduced by the first interposers 23 and the third interposers 25. Thus, it is possible to reduce or prevent the movement of the slider 100 in the downward direction and to achieve a reduction or prevention of the deterioration in the detection precision of the variable resistor.
In addition, in the present embodiment, the height H₃ of the upper surface 46 of each of the comb-like-pattern members 45 and the height H₂ of the upper surface 22a of each of the first and third interposers 23 and 25 are substantially the same, which enables the slider 100 to slide with almost no movement in the up-down direction. Thus, it is possible to achieve a reduction or prevention of the deterioration in the detection precision of the variable resistor.
Furthermore, in the present embodiment, the upper surface 46 of each of the comb-like-pattern members 45 and the upper surface 22a of each of the first and third interposers 23 and 25 are substantially parallel to each other, which enables the slider 100 to slide with almost no movement in the up-down direction. Thus, it is possible to achieve a reduction or prevention of the deterioration in the detection precision of the variable resistor.
Next, a method for manufacturing the variable resistor 1A in the above first embodiment will be described with reference to the drawings. FIG. 8(A) to FIG. 9(D) are sectional views illustrating an example of a method for manufacturing the variable resistor 1A in the first embodiment. The upper figures in FIG. 8(A) to FIG. 8(D) are sectional views each corresponding to the cross section taken along the line II-II in FIG. 1, and the lower figures in FIG. 8(A) to FIG. 8(D) are sectional views each corresponding to the cross section taken along the line III-III in FIG. 1. Likewise, the upper figures in FIG. 9(A) to FIG. 9(D) are sectional views each corresponding to the cross section taken along the line II-II in FIG. 1, and the lower figures in FIG. 9(A) to FIG. 9(D) are sectional views each corresponding to the cross section taken along the line III-III in FIG. 1.
First, as illustrated in FIG. 8(A), a release film 200 is prepared. In the present embodiment, the release film 200 includes a film 201 and a release layer 202 that is provided on one of the main surfaces of the film 201. The film 201 is constituted by a resin material. Examples of the resin material can include PET. The release layer 202 is formed by coating the film 201 with a release agent. Examples of the release agent can include a silicone-based release agent and a fluorine-based release agent. The release film 200 in the present embodiment corresponds to an example of a "support" in the present invention, and the release layer 202 in the present embodiment corresponds to an example of a "release-treated surface" in the present invention.
The second resist layer 50 is formed by printing the resist material on the release layer 202 of the release film 200 and solidifying (curing) the resist material. At this time, as illustrated in the upper figure in FIG. 8(A), an area where the opening 51 is to be formed is not coated with the resist material. In this manner, the second resist layer 50 having the opening 51 can be formed.
Note that, as a method of printing the resist material, either a contact coating method or a non-contact coating method may be used. Specific examples of the contact coating method can include screen printing, gravure printing, offset printing, gravure offset printing, and flexographic printing. Specific examples of the non-contact coating method can include inkjet printing, spray coating, dispense coating, and jet dispense. In addition, examples of a heat source used to cure the resist material can include, but not particularly limited to, an electric heating oven, an infrared oven, a far-infrared furnace (IR), a near-infrared furnace (NIR), and a laser emitting device, which may be combined to perform heat treatment.
Next, as illustrated in the lower figure in FIG. 8(B), a high-resistance conductive paste is printed on the second resist layer 50 and solidified (cured) to be formed into the resistor 40. As the high-resistance conductive paste, the conductive paste described above can be used. Examples of a printing method and a solidifying method of the high-resistance conductive paste can include, but not particularly limited to, the same methods as the printing method and the solidifying method of the second resist layer 50 mentioned above.
Next, as illustrated in FIG. 8(C), a low-resistance conductive paste is printed from the inside of the opening 51 to the resistor 40 and solidified (cured) to be formed into the comb-like-pattern members 45. As the low-resistance conductive paste, the conductive paste described above can be used. Examples of a printing method and a solidifying method of the low-resistance conductive paste can include, but not particularly limited to, the same methods as the printing method and the solidifying method of the second resist layer 50 mentioned above.
Next, as illustrated in FIG. 8(D), a low-resistance conductive paste is printed at both ends of the resistor 40 to be formed into the wiring patterns 31 and 35. As the low-resistance conductive paste, the conductive paste described above can be used. Examples of a printing method and a solidifying method of the low-resistance conductive paste can include, but not particularly limited to, the same methods as the printing method and the solidifying method of the second resist layer 50 mentioned above.
Note that the order of a step of forming the comb-like-pattern members 45 in FIG. 8(C) and a step of forming the wiring patterns 31 and 35 in FIG. 8(D) may be reversed. Alternatively, the steps may be integrated into a single step.
Next, as illustrated in FIG. 9(A), a resist material is printed on the release film 200 such that the wiring patterns 31 and 35, the resistor 40, the comb-like-pattern members 45, and the second resist layer 50 are covered with the resist material, and is solidified (cured) to be formed into the first resist layer 20. Examples of the resist material can include the same resist material as that constituting the second resist layer 50 mentioned above. Examples of a printing method and a solidifying method of the resist material can include, but not particularly limited to, the same methods as the printing method and the solidifying method of the second resist layer 50 mentioned above.
At this time, the resist material is solidified in the state where the spaces between the comb-like-pattern members 45 and the spaces between the second resist layer 50 and the comb-like-pattern members 45 are filled with the resist material, thus forming the first interposers 23 with which the spaces between the comb-like-pattern members 45 are filled and the third interposers 25 with which the spaces between the second resist layer 50 and the comb-like-pattern members 45 are filled. In addition, the resist material is printed and solidified such that the comb-like-pattern members 45 are covered with the resist material, thus forming the second interposers 24 mentioned above.
Next, as illustrated in FIG. 9(B), the base 11 is bonded to the first resist layer 20. As the base 11, for example, an adhesive tape including an adhesive layer (not illustrated) can be used as mentioned above, and the base 11 is bonded to the first resist layer 20 with the adhesive layer interposed therebetween.
Next, as illustrated in FIG. 9(C), the release film 200 is removed. In this manner, the lower membrane substrate 10A mentioned above is completed. In short, in the method for manufacturing the variable resistor 1A in the present embodiment, the lower membrane substrate 10A is prepared in such a manner that the first and second resist layers 20 and 50, the wiring patterns 31 and 35, the resistor 40, and the comb-like-pattern members 45 are prepared on the release film 200 before transferred to the base 11.
In the lower membrane substrate 10A prepared in this manner, the comb-like-pattern members 45 and the first resist layer 20 are formed directly on the release film 200 and then transferred. Thus, it is possible to easily expose the upper surfaces 46 of the comb-like-pattern members 45 through the protruding portion 22 of the first resist layer 20 in which the comb-like-pattern members 45 are embedded. For example, in the case where the first resist layer is formed after the comb-like-pattern members are formed on the base, the resist material is highly likely to adhere to the upper surfaces of the comb-like-pattern members. Thus, it is difficult to expose the upper surfaces of the comb-like-pattern members.
In addition, the upper surfaces 46 of the comb-like-pattern members 45, the upper surface 22a of the protruding portion 22 of the first resist layer 20 in which the comb-like-pattern members 45 are embedded, and the upper surface 50a of the second resist layer 50 are formed on the same main surface of the release film 200. Thus, it is possible to easily form the upper surfaces 46, 22a, and 50a such that the upper surfaces 46, 22a, and 50a are flush with one another.
In addition, the surface shape of the release film 200, which has high smoothness, can be transferred on the upper surfaces 46, 22a, and 50a. Thus, it is possible to form the upper surfaces 46, 22a, and 50a such that the upper surfaces 46, 22a, and 50a are smooth. For example, it is possible to set the surface roughness Ra of the upper surfaces 46, 22a, and 50a to 0.01 µm to 0.1 µm.
Next, as illustrated in FIG. 9(D), the upper membrane substrate 60A is bonded to the lower membrane substrate 10A with the spacer 90 interposed therebetween. Note that the wiring pattern 70 and the connector 80 of the lower membrane substrate 10A are formed by the printing on the lower surface 62 of the base 61 as mentioned above. In the above manner, the variable resistor 1A is manufactured.
Although the first resist layer 20, the wiring patterns 31 and 35, the resistor 40, the comb-like-pattern members 45, and the second resist layer 50 of the lower membrane substrate 10A are formed on the release film 200 and then transferred in the present embodiment, this is not limiting. The wiring patterns 31 and 35, the resistor 40, and the second resist layer 50 may be formed on the base 11 after at least the first resist layer 20 and the comb-like-pattern members 45 are formed on the release film 200 and then transferred to the base 11.

<<Second Embodiment>>

FIG. 10 is a plan view illustrating a variable resistor 1B in a second embodiment, and FIG. 11 is a sectional view taken along the line XI-XI in FIG. 10. FIG. 12 is a plan view illustrating a lower membrane substrate 10B of the variable resistor 1B in the second embodiment. FIG. 13 is a bottom view illustrating a spacer 90 and an upper membrane substrate 60B of the variable resistor 1B in the second embodiment.
As illustrated in FIG. 10 to FIG. 13, compared with the variable resistor 1A in the first embodiment, the variable resistor 1B in the present embodiment differs from the variable resistor 1A in the first embodiment in that its wiring pattern 70 is formed on the lower membrane substrate 10B rather than the upper membrane substrate 60B. Note that the rest of the configuration is the same as that of the first embodiment. The following will describe only the differences of the variable resistor 1B in the second embodiment from the first embodiment. The same components as those of the first embodiment will be given the same reference signs, and the description thereof will be omitted.
As illustrated in FIG. 11, the wiring pattern 70 in the present embodiment is formed on a base 11 via a first resist layer 20 interposed therebetween. The wiring pattern 70 includes a second body 71 and a second protective layer 72.
The second body 71 is formed by printing and solidifying (curing) a low-resistance conductive paste, as with the wiring patterns 31 and 35 mentioned above. More specifically, the second body 71 can be formed by printing and curing the low-resistance conductive paste on the second protective layer 72, which is formed inside an opening 51 of a second resist layer 50, in the step illustrated in FIG. 8(C).
The second body 71 is constituted by a material having a lower electric resistivity than a material constituting a resistor 40. The resistance value of the resistor 40 is sufficiently higher than the resistance value of the second body 71 such that the resistance value of the second body 71 can be considered to be negligible. Specifically, the resistance value of the resistor 40 is at least 10 times the resistance value of the second body 71 and is preferably at least 100 times the resistance value of the second body 71. The electric resistivity of the material constituting the resistor 40 is at least 10 times the electric resistivity of the material constituting the second body 71 and is preferably at least 100 times the electric resistivity of the material constituting the second body 71.
As illustrated in FIG. 12, the second body 71 extends along an X direction in the drawing. The second body 71 includes, at one of its ends, a parallel portion 711 that extends substantially parallel to the resistor 40. Note that the planar shape of the second body 71 is not particularly limited to the planar shape described above.
The second protective layer 72 of the wiring pattern 70 covers the parallel portion 711 of the second body 71. The second protective layer 72 is a layer that protects the parallel portion 711 of the second body 71. The second protective layer 72 is formed by printing and curing a high-resistance conductive paste having a high electrical resistance value compared with the low-resistance conductive paste mentioned above. For example, the second protective layer 72 can be formed by printing and curing the high-resistance conductive paste inside the opening 51 of the second resist layer 50 in the step illustrated in FIG. 8(B).
Specific examples of such a high-resistance conductive paste can include, but not particularly limited to, a carbon paste. The second protective layer 72 has a length approximately the same as that of the resistor 40 in the X direction in the drawing. The second protective layer 72 is disposed separate from the resistor 40 and the comb-like-pattern members 45 with predetermined gaps. That is, the second protective layer 72 of the wiring pattern 70 is disposed substantially parallel to the resistor 40 and substantially parallel to a direction in which the comb-like-pattern members 45 are arrayed. Note that the wiring pattern 70 need not include the second protective layer 72.
In contrast, as illustrated in FIG. 10, FIG. 11, and FIG. 13, a connector 80 in the present embodiment is not connected to the wiring pattern 70 as in the first embodiment. In the present embodiment, the connector 80 has a planar shape that is rectangular and has a larger width than the connector 80 in the first embodiment. In plan view, the connector 80 is provided on a lower surface 62 of the base 61 such that an edge 80a, which is one of edges (the edge on the -Y side extending along the X direction in the drawing) of the connector 80, overlaps the comb-like-pattern members 45 and an edge 80b, which is the other of the edges (the edge on the +Y side extending along the X direction in the drawing) of the connector 80, overlaps the wiring pattern 70.
As illustrated in FIG. 11, in the variable resistor 1B in the present embodiment, the pressing of a slider 100 bends the base 61 of the upper membrane substrate 60B downward, bringing the connector 80 into contact with one of the comb-like-pattern members 45 and the wiring pattern 70. Thus, the resistor 40 and the wiring pattern 70 are electrically connected together via the connector 80. The slider 100 sliding on the upper membrane substrate 60B along the X direction while pressing the upper membrane substrate 60B changes the position of a connection between the connector 80 and the resistor 40, thus causing the resistive length (resistance value) of the resistor 40 to vary.
More specifically, as mentioned above, a power supply voltage (e.g., 5 [V]) is applied to the wiring pattern 31, which is one of the wiring patterns connected to the resistor 40, while the wiring pattern 35, which is the other of the wiring patterns connected to the resistor 40, is grounded. In addition, the pressing of the slider 100 constantly establishes an electric connection of the wiring pattern 70 to the resistor 40 via the connector 80, and the wiring pattern 70 is electrically connected to the resistor 40 at a given position in the X direction in the drawing. As a result, the wiring pattern 70 detects a voltage (detected voltage) that changes as a function of the pressing position of the slider 100. That is, in the present embodiment, the resistance value between the wiring patterns 31 and 70 changes in accordance with the pressing position of the slider 100. To the wiring patterns 31 and 70 of the variable resistor 1B, a multimeter (not illustrated) or the like is connected. The multimeter or the like outputs a potential difference between a power supply voltage and the detected voltage of the wiring pattern 70.
For example, in the case where the slider 100 is positioned at the left end of the slidable area SA in FIG. 10, the position of the connection of the connector 80 is also positioned at the left end of the resistor 40. Thus, the wiring pattern 70 detects a voltage indicating substantially the same potential as the power supply voltage, and the multimeter or the like outputs the potential difference between the power supply voltage and the detected voltage of the wiring pattern 70 (e.g., 0 [V]).
In contrast, as illustrated in FIG. 10, in the case where the slider 100 is positioned substantially at the center of the slidable area SA, the position of the connection of the connector 80 is also positioned substantially at the center of the resistor 40. Thus, the wiring pattern 70 detects a voltage indicating a potential substantially half the potential indicated by the power supply voltage, and the multimeter or the like outputs the potential difference between the power supply voltage and the detected voltage of the wiring pattern 70 (e.g., 2.5 [V]).
In addition, in the case where the slider 100 is positioned substantially at the right end of the slidable area SA in FIG. 10, the position of the connection of the connector 80 is also positioned substantially at the right end of the resistor 40. Thus, the wiring pattern 70 detects a voltage indicating a potential substantially the same potential as the ground, and the multimeter or the like outputs the potential difference between the power supply voltage and the detected voltage of the wiring pattern 70 (e.g., 5 [V]).
Also in the second embodiment, the spaces between the comb-like-pattern members 45 are filled with first interposers 23. Thus, it is possible to reduce or prevent the degradation of the comb-like-pattern members 45 and to reduce or prevent the deterioration in the detection precision of the variable resistor 1B, as in the above first embodiment.

<<Third Embodiment>>

FIG. 14 is a plan view illustrating a variable resistor 1C in a third embodiment, and FIG. 15 is a sectional view taken along the line XV-XV in FIG. 14. FIG. 16 is a plan view illustrating a lower membrane substrate 10C of the variable resistor 1C in the third embodiment.
As illustrated in FIG. 14 to FIG. 16, compared with the variable resistor 1B in the second embodiment, the variable resistor 1C in the present embodiment differs from the second embodiment in that (1) the lower membrane substrate 10C includes a plurality of comb-like-pattern members 75a to 75i and in that (2) a connector 80 does not overlap a wiring pattern 70. The rest of the configuration is the same as that of the second embodiment. The following will describe only the differences of the variable resistor 1C in the third embodiment from the second embodiment. The same components as those of the second embodiment will be given the same reference signs, and the description thereof will be omitted. Note that, in the present embodiment, the comb-like-pattern members 75a to 75i may be collectively referred to as "comb-like-pattern members 75."
The comb-like-pattern members 75 are formed by printing and curing a low-resistance conductive paste, as with comb-like-pattern members 45. As illustrated in FIG. 14, the comb-like-pattern members 75 in the present embodiment are provided between a resistor 40 and the wiring pattern 70. Note that the comb-like-pattern members 75 in the present embodiment correspond to an example of "second comb-like-pattern members" in the present invention.
As illustrated in FIG. 16, the comb-like-pattern members 75a to 75i each have a planar shape that is linear and branch off from a second body 71 of the wiring pattern 70 to extend along a Y direction in the drawing. The comb-like-pattern members 75a to 75i also protrude from the wiring pattern 70 toward the resistor 40. That is, the comb-like-pattern members 75a to 75i are connected to the wiring pattern 70 and extend to below a slidable area SA. The comb-like-pattern members 75a to 75i are arranged at substantially regular intervals and substantially parallel to one another.
As illustrated in FIG. 14, all the comb-like-pattern members 45a to 45j and 75a to 75i face the connector 80 through an opening 91 of a spacer 90 and overlap the slidable area SA of a slider 100 in plan view. As illustrated in FIG. 14 to FIG. 16, in plan view, the comb-like-pattern members 45a to 45j and the comb-like-pattern members 75a to 75i are alternately arranged along an X direction in the drawing and are disposed at substantially regular intervals.
Note that the numbers of the comb-like-pattern members 45 and 75 are not particularly limited to the above. In addition, the disposition of the comb-like-pattern members 45 and 75 is not particularly limited to the above. In this regard, the more the numbers of the comb-like-pattern members 45 and 75, the more the resolution of the output of the variable resistor 1C can be increased, as will be described later. In addition, the intervals between the comb-like-pattern members 45 and 75 are not limited to regular intervals as long as the intervals are provided between the comb-like-pattern members 45 and 75.
First interposers 23 of a first resist layer 20 in the present embodiment include portions with which the spaces between the comb-like-pattern members 45 are filled, portions with which the spaces between the comb-like-pattern members 75 are filled, and portions with which the spaces between the comb-like-pattern members 45 and the comb-like-pattern members 75 are filled, and the portions are connected together. As a result, the first interposers 23 have a planar shape that is a zigzag shape extending in the X direction.
Third interposers 25 include portions with which the spaces between a second resist layer 50 and the comb-like-pattern members 75a and 75i are filled in addition to portions with which the spaces between the second resist layer 50 and the comb-like-pattern members 45a and 45j are filled. As a result, the third interposers 25 each have a planar shape that is an L shape.
As illustrated in FIG. 14 and FIG. 15, the pressing of the slider 100 bends a base 61 of an upper membrane substrate 60B downward, bringing the connector 80 into contact with one of the comb-like-pattern members 45 and one of the comb-like-pattern members 75 that are adjacent to each other. This electrically connects the resistor 40 and the wiring pattern 70 together via the connector 80. Specifically, in the state illustrated in FIG. 15, the comb-like-pattern member 45f of the comb-like-pattern members 45a to 45j and the comb-like-pattern member 75e of the comb-like-pattern members 75a to 75i are electrically connected together via the connector 80.
Note that the number of the comb-like-pattern members 45a to 45j that are connected to the connector 80 at the same time by the pressing of the slider 100 may be more than one. Likewise, the number of the comb-like-pattern members 75a to 75j that are connected to the connector 80 at the same time by the pressing of the slider 100 may be more than one.
In the present embodiment, the slider 100 sliding on the upper membrane substrate 60B while pressing the upper membrane substrate 60B sequentially changes the combination of one of the comb-like-pattern members 45 and one of the comb-like-pattern members 75 connected by the connector 80, thus causing the resistive length (resistance value) of the resistor 40 to vary.
For example, in the state illustrated in FIG. 15, the comb-like-pattern members 75e and 45f are connected together via the connector 80 as mentioned above. As the slider 100 slides in the +X direction in the drawing from this state, the combination of the comb-like-pattern members connected via the connector 80 is changed in the sequence such as comb-like-pattern members 75e and 45f -> comb-like-pattern members 45f and 75f -> comb-like-pattern members 75f and 45g -> comb-like-pattern members 45g and 75g -> comb-like-pattern members 75g and 45h -> ... -> comb-like-pattern members 45i and 75i -> comb-like-pattern members 75i and 45j.
With these changes, the wiring pattern 70 connected to the comb-like-pattern members 75a to 75i detects a voltage (detected voltage) that changes as a function of the combination of one of the comb-like-pattern members 45 and one of the comb-like-pattern members 75 that are connected via the connector 80. That is, also in the present embodiment, the resistance value between the wiring patterns 31 and 70 changes in accordance with the pressing position of the slider 100. In the case where the slider 100 slides in the +X direction in the drawing, the resistance value between the wiring patterns 31 and 70 gradually increases with the sliding of the slider 100. To the wiring patterns 31 and 70 of the variable resistor 1C, a multimeter or the like is connected. The multimeter or the like outputs a potential difference between a power supply voltage and the detected voltage of the wiring pattern 70.
In contrast, in the case where the slider 100 slides in the -X direction in the drawing in the state illustrated in FIG. 15, the combination of the one of comb-like-pattern members connected via the connector 80 is changed with the sliding of the slider 100 in the sequence such as comb-like-pattern members 45f and 75e -> comb-like-pattern members 75e and 45e -> comb-like-pattern members 45e and 75d -> comb-like-pattern members 75d and 45d -> comb-like-pattern members 45d and 75c -> ... -> comb-like-pattern members 45b and 75a -> comb-like-pattern members 75a and 45a. In this case, the resistance value between the wiring patterns 31 and 70 gradually decreases with the sliding of the slider 100.
Also in the third embodiment, the spaces between the comb-like-pattern members 45 and 75 are filled with the first interposers 23. Thus, it is possible to reduce or prevent the degradation of the comb-like-pattern members 45 and 75 and to reduce or prevent the deterioration in the detection precision of the variable resistor 1C, as in the above first embodiment.
The embodiments explained above are described to facilitate understanding of the present invention and are not described to limit the present invention. It is therefore meant that the constituent elements disclosed in the above embodiments include all design changes and equivalents falling within the technical scope of the present invention.
For example, although the comb-like-pattern members 45 are formed on the lower membrane substrate 10A in the first to third embodiments, the comb-like-pattern members 45 may be formed on the upper membrane substrate 60A, which is pressed with the slider 100.
In the first to third embodiments, the variable resistors 1A to 1C are operated with the slider 100, which is included in the variable resistors 1A to 1C themselves. However, this is not particularly limiting. For example, the variable resistors may be operated with a finger of an operator instead of the slider 100.
In the embodiments mentioned above, the resistance value of each of the variable resistors 1A to 1C is detected by obtaining the detected voltage of the wiring pattern 70, with the wiring pattern 31 connected to the power supply and the wiring pattern 35 connected to the ground. However, the circuit configuration for detecting the resistance value of each variable resistor is not particularly limited to this circuit configuration.
For example, the power supply may be connected to the wiring patterns 31 and 70, without the provision of the wiring pattern 35. Even in this case, the resistance value between the wiring patterns 31 and 70 changes in accordance with the position of the pressing of the slider 100.

[EXPLANATIONS OF LETTERS OR NUMERALS]

1A to 1C: variable resistor
10A to 10C: lower membrane substrate
11: base
11a: upper surface
20: first resist layer
21: reduced-thickness portion
21a: upper surface
22: protruding portion
22a: upper surface
23: first interposer
23a: first exposed portion
23b, 23c: first and second unexposed portions
24: second interposer
25: third interposer
31: wiring pattern
35: wiring pattern
40: resistor
45, 45a to 45j: comb-like-pattern member
46: upper surface
47: lower surface
48a: second exposed portion
48b, 48c: third and fourth unexposed portions
50: second resist layer
50a: upper surface
51: opening
60A, 60B: upper membrane substrate
61: base
62: lower surface
63: upper surface
70: wiring pattern
71: second body
711: parallel portion
72: second protective layer
75, 75a to 75i: comb-like-pattern member
76: second top edge surface
80: connector
80a,: 80b edge
81: first body
82: first protective layer
90: spacer
91: opening
100: slider
110: presser
200: release film
201: film
202: release layer
NA: non-overlapping area
SA: slidable area

Claims

A variable resistor comprising:
a first base;

comb-like-pattern members supported by the first base and extending with intervals therebetween; and

an insulator disposed on the first base such that spaces between the comb-like-pattern members are filled with the insulator, wherein

the comb-like-pattern members have top edge surfaces on a side opposite to the first base, and

the top edge surface is exposed through the insulator.
The variable resistor according to claim 1, wherein
the insulator includes a first main surface on the side opposite to the first base, and

a height of the top edge surface from the first base is substantially identical to a height of the first main surface from the first base.
The variable resistor according to claim 1, wherein
the insulator includes a first main surface on the side opposite to the first base, and

the first main surface extends substantially parallel to the first base.
The variable resistor according to claim 1, wherein
the insulator comprises:
a first interposer interposed between the comb-like-pattern members; and

a second interposer interposed between the first base and the comb-like-pattern member.
The variable resistor according to claim 1, wherein
the insulator includes a first main surface on the side opposite to the first base,

the variable resistor includes a resistor,

the comb-like-pattern members include first comb-like-pattern members connected to the resistor,

the first comb-like-pattern members each include:
a first portion in which the top edge surface is exposed through the insulator; and

a second portion formed integrally with the first portion and connected to the resistor, and

a thickness of the second portion is smaller than a thickness of the first portion in a first direction perpendicular to the first main surface.
The variable resistor according to claim 1, wherein
the variable resistor comprises:
a resistor disposed on the first base;

a first wiring pattern disposed on the first base and connected to the resistor;

a spacer including an opening;

a second base stacked on the first base with the spacer interposed therebetween;

a connector disposed on the second base such that the connector is located in the opening, the connector being configured to be electrically connected to the resistor by pressing of a slider from an outside of the second base; and

a second wiring pattern disposed on the second base and connected to the connector, or disposed on the first base and configured to be electrically connected to the connector by the pressing of the slider,

the connector includes a non-overlapping area where the connector does not overlap the resistor in plan view,

a slidable area where the slider is slidable is included in the non-overlapping area in plan view,

the top edge surface is a surface of each of the comb-like-pattern members, the surface facing the connector, and

a resistance value between the first wiring pattern and the second wiring pattern changes in accordance with a position of the slider.
The variable resistor according to claim 6, wherein
the second wiring pattern is disposed on the second base and connected to the connector,

the comb-like-pattern members include a first comb-like-pattern members connected to the resistor,

the first comb-like-pattern members overlap the slidable area in plan view,
and

the connector is brought into contact with the first comb-like-pattern members by the pressing of the slider from the outside of the second base.
The variable resistor according to claim 6, wherein
the second wiring pattern is disposed on the first base,

the plurality of comb-like-pattern members include first comb-like-pattern members connected to the resistor, the first comb-like-pattern members and the second wiring pattern overlapping the slidable area in plan view, and

the connector is brought into contact with the first comb-like-pattern members and the second wiring pattern by the pressing of the slider from the outside of the second base.
The variable resistor according to claim 6, wherein
the second wiring pattern is disposed on the first base,

the comb-like-pattern members include:
first comb-like-pattern members connected to the resistor; and

second comb-like-pattern members connected to the second wiring pattern,

the first and second comb-like-pattern members overlap the slidable area in plan view,

the first comb-like-pattern members and the second comb-like-pattern members are alternately arranged in the slidable area along a direction in which the connector extends, and

the connector is brought into contact with the first comb-like-pattern members and the second comb-like-pattern members by the pressing of the slider from the first base.
The variable resistor according to claim 6, wherein
the variable resistor further comprises a third wiring pattern disposed on the first base and connected to the resistor,

the comb-like-pattern members include:
a third comb-like-pattern member connected to the first wiring pattern; and

a fourth comb-like-pattern member connected to the third wiring pattern, and

the third and fourth comb-like-pattern members overlap the slidable area in plan view.
A method for manufacturing the variable resistor according to any one of claims 1 to 10, the method comprising:
a first step of preparing a support including a release-treated surface;

a second step of forming the comb-like-pattern members on the release-treated surface of the support;

a third step of forming the insulator on the release-treated surface such that spaces between the comb-like-pattern members are filled with the insulator; and

a fourth step of transferring the comb-like-pattern members and the insulator from the support to the first base.