Transparent heater

Abstract

To adjust the resistance value of a wiring layer without changing the cross-sectional area of the wiring layer.SOLUTION: A transparent heater 1 includes a transparent substrate 5 in which a bottomed first groove 8 extending linearly is formed on an upper surface, and a first wiring layer 32 embedded in the first groove 8 and having conductivity. The first wiring layer 32 contains impurities.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to transparent heaters. [Background technology]

[0002] 2. Description of the Related Art Conventionally, techniques for forming wiring on a flexible substrate have been known.

[0003] For example, Patent Document 1 discloses a technique for forming a copper-based plating layer on a base film using a resist pattern as a flexible printed wiring board and a manufacturing method thereof. Specifically, Patent Document 1 describes forming a resist pattern on a film on which a conductive underlayer is laminated, passing a current through the conductive underlayer to perform electroplating, and then removing the resist by etching.

[0004] Furthermore, Patent Document 2 discloses a transparent conductive film that includes a transparent film having grooves on the surface and conductive portions that exist in the grooves of the transparent film. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2021 / 200614 [Patent Document 2] Patent Publication No. 2021-163571 Summary of the Invention [Problem to be solved by the invention]

[0006] When a transparent conductive film is used as a heater (resistance heating element), it is expected to be operated at a constant voltage. Generally, the amount of heat generated by a heater is proportional to the resistance of the heating wire and the square of the current flowing through the heating wire. Therefore, in order to control the amount of heat generated by the heater within a certain range, it is necessary to adjust the cross-sectional area of ​​the wiring layer used as the heating wire. Conventionally, high resistance has been achieved by narrowing the wiring width of the wiring layer or increasing the wiring length, which has led to issues such as difficulty in miniaturization and inability to meet design standards other than electrical resistance. Furthermore, reducing the cross-sectional area of ​​the wiring layer may result in a decrease in reliability.

[0007] In Patent Document 1, the resistivity of a flexible printed wiring board is adjusted by adjusting the sulfur and carbon concentrations in the plating film. Furthermore, the electrical resistance of the wiring is increased by adjusting the additives in the plating solution. The flexible printed wiring board in Patent Document 1 is formed using a so-called semi-active method, which includes a plating process in which copper-based plating is formed by electroplating the conductive underlayer of a base film in a plating solution, and a removal process in which the resist pattern and non-laminated areas of the copper-based plating layer are removed. However, metal wiring formed using the semi-additive method has three exposed sides, which significantly reduces chemical resistance and corrosion resistance due to an increase in impurity concentration.

[0008] The present disclosure has been made in view of the above points, and its purpose is to make it possible to adjust the resistance value of a wiring layer used as a heating wire without changing the cross-sectional area of ​​the wiring layer. [Means for solving the problem]

[0009] In order to achieve the above object, a transparent heater according to one embodiment of the present disclosure comprises a transparent substrate having a linearly extending, bottomed groove formed on its upper surface, and a first wiring layer that is embedded in the groove and has conductivity, and the first wiring layer contains impurities. [Effects of the Invention]

[0010] The transparent heater of the present disclosure can adjust the resistance of the wiring layer used as the heating wire without changing the cross-sectional area of ​​the wiring layer. Furthermore, since the first wiring layer is embedded in the groove, chemical resistance and corrosion resistance can be improved. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 2 is a plan view schematically illustrating the overall configuration of the touch sensor. [Figure 2] FIG. 2 is a cross-sectional view taken along line II-II in FIG. [Figure 3] FIG. 3 is a cross-sectional view taken along line III-III in FIG. [Figure 4] FIG. 3 is a diagram showing a modification of FIG. 2. [Figure 5] FIG. 3 is a diagram showing another modified example of FIG. 2. [Figure 6] FIG. 10 is a diagram showing the relationship between impurity concentration and resistivity. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. The following description of the embodiments is merely exemplary in nature and is not intended to limit the present disclosure, its applications, or its uses.

[0013] FIG. 1 shows the configuration of a transparent heater 1 according to an embodiment of the present disclosure. In this embodiment, an example is shown in which the transparent heater 1 is rectangular in plan view. However, the shape of the transparent heater 1 is not particularly limited and may be any shape in plan view. For example, the transparent heater 1 may be circular, elliptical, polygonal, or other shapes in plan view.

[0014] The transparent heater 1 comprises a transparent substrate 5 having a linearly extending groove with a bottom formed on its upper surface, and a first wiring layer 32 (see Figure 2) having conductivity and embedded in a first groove 8 (see Figure 2) of the substrate.

[0015] -substrate- As shown in Fig. 2, the substrate 5 has a film substrate 6 and a groove-formed layer 7 laminated on the upper side of the film substrate 6. The up-down direction is determined for the convenience of explanation and has no particular meaning other than that of the present disclosure. In other words, the directions shown in the present disclosure are not intended to determine or limit the directions during the manufacture or use of the transparent heater 1.

[0016] In this embodiment, an example is shown in which the substrate 5 has a rectangular shape in a plan view. The shape of the substrate 5 is not particularly limited, and can be any shape in a plan view depending on the shape of the transparent heater 1. For example, the substrate 5 may have a circular, elliptical, polygonal, or other shape in a plan view.

[0017] The film substrate 6 is made of a transparent resin material, such as PET (polyethylene terephthalate), polycarbonate, COP (cycloolefin polymer), or COC (cycloolefin copolymer).

[0018] As shown in FIGS. 2 and 3, the groove forming layer 7 is a layer for forming the first groove portion 8 and the second groove portion 9. The groove forming layer 7 is made of an insulating and light-transmitting resin material. The groove forming layer 7 has a shape-imparting property for forming grooves. The groove forming layer 7 also serves to firmly bond the first adhesive layers 31, 41 (described below) in the groove portions 8, 9 to the film substrate 6. The thickness of the groove forming layer 7 is, for example, 2.0 μm to 17.0 μm.

[0019] [First groove, second groove] The first groove portions 8 (corresponding to groove portions) extend linearly to form a predetermined pattern on the upper surface of the groove-forming layer 7, i.e., the upper surface 5a of the substrate 5. In the example of FIG. 1, the first groove portions 8 are linearly extending in the X direction. Examples of the predetermined pattern include a mesh pattern, a wave pattern, a pattern combining ellipses, and a linear pattern. For example, in the case of a mesh pattern, the first groove portions 8 extend obliquely with respect to both the first direction X and the second direction Y at predetermined intervals, forming a network structure in which diamond-shaped cells are regularly arranged.

[0020] As shown in FIG. 2, the first grooves 8 are recessed downward from the upper surface 5a of the substrate 5 (in the thickness direction of the substrate 5 from the groove-forming layer 7 toward the film substrate 6) and have a bottom. In this embodiment, a plurality of first grooves 8 are formed at predetermined intervals (e.g., equal intervals) in the Y direction, and the groove depths and groove widths of the first grooves 8 are the same. For example, the groove depth D1 of the first grooves 8 is set to be 0.5 μm or more and 10.0 μm or less. More preferably, the groove depth D1 is set to be 0.5 μm or more and 2.0 μm or less.

[0021] In the present disclosure, "the same size" refers to the same size at the time of design, and includes a case in which the groove depth dimensions of the first groove portions 8 and the groove width dimensions of the first groove portions 8 are slightly different from one another due to manufacturing errors, manufacturing variations, etc. In other words, "the same size" includes those that are substantially the same size. The same applies to the second groove portion 9 described below, and "the same size" also includes those that are substantially the same size.

[0022] Similar to the first groove portions 8, the second groove portions 9 extend linearly to form a predetermined pattern on the upper surface of the groove formation layer 7, i.e., on the upper surface 5a of the substrate 5. An example of the predetermined pattern is a pattern in which a plurality of first groove portions 8 are arranged linearly or in a ladder shape.

[0023] As shown in FIG. 3, the second groove portions 9 are formed with a bottom recessed downward from the upper surface 5a of the substrate 5 (in the thickness direction of the substrate 5 from the groove-forming layer 7 toward the film substrate 6). In the example of FIG. 1, the second groove portions 9 extend in the Y direction at both ends of the first groove portions 8 in the X direction and are connected to each of the multiple first groove portions 8. The second groove portions 9 have the same groove depth and groove width. The groove depth D2 of the second groove portions 9 is, for example, 0.5 μm or more and 10.0 μm or less. More preferably, the groove depth D2 is 0.5 μm or more and 2.0 μm or less. The groove depth D1 of the first groove portions 8 and the groove depth D2 of the second groove portions 9 may be different from each other. Furthermore, when multiple first groove portions 8 are provided, the groove depth D1 of the first groove portions 8 may be different from each other. Similarly, when multiple second groove portions 9 are provided, the groove depth D2 of the second groove portions 9 may be different from each other.

[0024] In this embodiment, as shown in Figures 2 and 3, fillets are formed at the corners between the side and bottom surfaces of each of the first grooves 8 and the second grooves 9. However, fillets do not have to be formed at the corners. That is, the bottom surfaces of the first grooves 8 and / or the second grooves 9 may be flat or curved (not shown). Furthermore, the side surfaces of the first grooves 8 and / or the second grooves 9 may be inclined so as to gradually widen from the bottom surfaces toward the openings (not shown).

[0025] [Heating wire] The heating wire 24 is embedded in the first groove 8 and includes a first wiring layer 32 having electrical conductivity, and a first covering layer 35 laminated above the first wiring layer 32. In other words, the heating wire 24 (first wiring layer 32) has the same pattern shape as the first groove 8. The heating wire 24 generates a heat amount that is proportional to the resistance value of the heating wire 24 and the square of the value of the current flowing through the heating wire supplied from the power source EV.

[0026] The wire width dimension of the heating wire 24 (dimension w1 shown in FIG. 2) is the same as the groove width dimension L1 of the first groove portion 8, and is, for example, 0.5 μm or more and 20.0 μm or less. More preferably, the wire width dimension w1 of the heating wire 24 is 1.50 μm or more and 10.0 μm or less. The surface roughness Ra of the heating wire 24 is set to, for example, 0.01 μm or more and 0.50 μm or less. As a result, the electrical conductivity reliability of the heating wire 24 is easily ensured. This suppresses reflection (specular reflection) of external light, such as sunlight or illumination light, on the surface of the first wiring layer 32. As a result, the heating wire 24 becomes difficult to see when viewed by the user, preventing so-called "line visibility." Furthermore, by setting the surface roughness Ra of the heating wire 24 within the above numerical range, the electrical conductivity reliability of the heating wire 24 is easily ensured.

[0027] The first wiring layer 32 includes a first seed layer 33 and a first main layer 34. Both the first seed layer 33 and the first main layer 34 are conductive. The first wiring layer 32 includes a conductive metal such as copper (Cu) or silver (Ag). Alternatively, instead of the conductive metal, the first wiring layer 32 may include a transparent conductive material having optical transparency, such as a conductive resin material, indium tin oxide, or tin oxide. In the following description, an example in which copper (Cu) is used as the conductive metal will be described.

[0028] To ensure adhesion of the first wiring layer 32 to the first grooves 8, a first adhesion layer 31 may be provided between the first grooves 8 and the first wiring layer 32. The first adhesion layer 31 is a metal layer made of, for example, a metal nitride containing one or more metals selected from the group consisting of Ti, Al, V, W, Ta, Si, Cr, Ag, Mo, Cu, and Zn, a metal oxide, or a metal oxynitride containing both a metal nitride and a metal oxide. The first adhesion layer 31 is formed in the first grooves 8 by, for example, vapor deposition or sputtering. The first adhesion layer 31 has the function of making the heating wire 24 less visible when a user looks at the transparent heater 1.

[0029] The first seed layer 33 improves adhesion between the first adhesion layer 31 and the first main layer 34. Specifically, the first seed layer 33 functions as a cathode for depositing a plating solution such as copper (Cu) on the first adhesion layer 31, for example, during electroplating to form the first main layer 34. The first seed layer 33 is deposited as a thin film on the first adhesion layer 31 by, for example, vapor deposition or sputtering. Note that if the first main layer 34 is formed by a method other than electroplating, the first seed layer 33 may not be provided.

[0030] The first main layer 34 is formed by, for example, vapor deposition, sputtering, electroless plating, or electroplating. In this embodiment, the first main layer 34 is laminated on the first seed layer 33 by electroplating. After the electroplating, the first seed layer 33 and the first main layer 34 are integrally formed, and the interface between the first seed layer 33 and the first main layer 34 cannot be distinguished.

[0031] The first wiring layer 32 contains impurities. The impurities are, for example, organic substances containing carbon atoms or sulfur atoms. The resistivity of the first wiring layer 32 is higher than the resistivity of pure copper. In other words, the resistivity of the first wiring layer 32 is 1.68×10 -8 Higher than [Ω·m].

[0032] Fig. 6 shows an example of the relationship between the impurity concentration and resistivity of the first wiring layer 32. As shown in Fig. 6, the resistivity of the first wiring layer 32 increases according to the impurity concentration of the first wiring layer 32. Therefore, by adjusting the impurity concentration of the first wiring layer 32, the resistance value of the first wiring layer 32, and therefore the resistance value of the heating wire 24, can be controlled.

[0033] The method for incorporating impurities into the first wiring layer 32 is not particularly limited. For example, the substrate 5 on which the first wiring layer 32 is formed is immersed in a liquid containing impurities, thereby injecting the impurities into the first wiring layer 32. The liquid containing impurities may be an organic substance containing carbon atoms or sulfur atoms as impurities. Alternatively, for example, the substrate 5 on which the first wiring layer 32 is formed may be immersed in a liquid containing impurities. Examples of impurities include organic substances such as surfactants and / or sulfur-based organic compounds. The concentration of the impurities may be selected depending on the plating concentration. The impurity concentration of the first wiring layer 32 may be set to gradually decrease from the top surface downward.

[0034] The first covering layer 35 is laminated above the first wiring layer 32 (first main body layer 34). The electrode covering layer 45 has the function of making the heating wire 24 less visible to a user of the transparent heater 1. The reflectance of the first covering layer 35 for visible light wavelengths is lower than the reflectance of the first wiring layer 32 for visible light wavelengths. For example, the reflectance of the first covering layer 35 for visible light wavelengths is 20% or more and 95% or less. More preferably, it is 20% or more and 65% or less. Furthermore, the resistivity of the first covering layer 35 is higher than the resistivity of the first wiring layer 32.

[0035] The first coating layer 35 is formed by, for example, vapor deposition, sputtering, electrolytic plating, or electroless plating. This embodiment illustrates an example in which the first coating layer 35 is laminated on the first wiring layer 32 by electroless plating. The composition of the electroless plating solution used in the electroless plating is not particularly limited. This embodiment illustrates, as an example, an example in which palladium (Pd) is used as a constituent atom of the first coating layer 35. In this case, the first coating layer 35 is formed, for example, by substituting copper crystal grains located at the boundaries (so-called "grain boundaries") between copper crystal grains located on the upper surface of the first wiring layer 32 with palladium (blackening treatment). Specifically, in the blackening treatment, intergranular corrosion progresses along the boundaries (grain boundaries) between copper crystal grains located on the upper surface of the first wiring layer 32, substituting copper crystal grains that form the upper surface of the first wiring layer 32 with palladium. This results in the first coating layer 35 being laminated on the upper surface of the first wiring layer 32. The same applies to the case where palladium (Pd) is used as a constituent atom of the electrode coating layer 45 described later.

[0036] 〔electrode〕 Returning to Fig. 1, the transparent heater 1 has a pair of electrodes 25 connected to both ends of a heating wire 24. The electrodes 25 are connected to a power source EV via conductors 26 such as lead wires. The transparent heater 1 functions as a heater when a current flows from the power source EV through the conductors 26 and the electrodes 25 to the heating wire 24, causing the heating wire 24 to generate heat.

[0037] 3, the electrode 25 includes a conductive electrode wiring layer 42 embedded in the second groove 9, and an electrode covering layer 45 laminated on the upper surface of the electrode wiring layer 42. The electrode 25 has a predetermined pattern (e.g., a ladder-like pattern). The line width dimension of the electrode 25 (dimension w2 shown in FIG. 3) is the same as the groove width dimension L2 of the second groove 9, and is, for example, not less than 1.0 μm and not more than 20.0 μm.

[0038] The electrode wiring layer 42 includes an electrode seed layer 43 and an electrode main layer 44. Both the electrode seed layer 43 and the electrode main layer 44 are conductive and are made of, for example, copper (Cu).

[0039] In order to ensure adhesion of the electrode wiring layer 42 to the second groove portion 9, an electrode adhesion layer 41 may be provided between the second groove portion 9 and the electrode wiring layer 42. The electrode adhesion layer 41 is, for example, a metal layer made of the same compound as the first adhesion layer 31. The electrode adhesion layer 41 is formed in the second groove portion 9 by, for example, vapor deposition or sputtering.

[0040] The electrode covering layer 45 is laminated on the upper surface of the electrode wiring layer 42 (electrode main layer 44). The thickness of the electrode covering layer 45 (reference numeral d2 shown in FIG. 3) is, for example, not less than 0.01 μm and not more than 5.0 μm.

[0041] [Other embodiments] Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments, and various modifications are possible within the scope of the present disclosure.

[0042] For example, the heating wire 24 described in the above embodiment may be configured without the first covering layer 35.

[0043] For example, as shown in Fig. 4, the heating wire 24 may not be provided with the first coating layer 35, but may instead have a second wiring layer 36 embedded in the first groove 8 and stacked above the first wiring layer 32. In other words, the wiring layer of the heating wire 24 may have a two-layer structure. In this case, the resistivity of the second wiring layer 36 is higher than the resistivity of the first wiring layer 32. Specifically, for example, the first wiring layer 32 may be copper containing impurities, and the second wiring layer 36 may be a metal layer containing nickel.

[0044] This offers the advantages of a better appearance and higher reliability. For example, forming a layer with a relatively high resistance as the second wiring layer 36 increases the resistance of the heating wire 24, while forming a wiring layer with a relatively low resistance decreases the resistance of the heating wire 24. This allows for more precise control of the resistance compared to when the wiring layer has a single-layer structure. In other words, it is possible to accommodate a variety of resistance values ​​while keeping the cross-sectional area of ​​the heating wire 24 the same.

[0045] 4, the relationship between the resistivity of the first wiring layer 32 and the resistivity of the second wiring layer 36 is not limited to the above, and the resistivity of the first wiring layer 32 may be higher than the resistivity of the second wiring layer 36. In that case, for example, the first wiring layer 32 is a metal layer containing nickel, and the second wiring layer is copper containing impurities. This configuration has the effect of improving the adhesion of the wiring.

[0046] Furthermore, the second wiring layer 36 may contain impurities in addition to or instead of the first wiring layer 32. The impurities in this case may be the same as those in the above embodiment, or may be different from those in the above embodiment.

[0047] 5, the upper surface of the first wiring layer 32 may include a first surface 32a exposed toward the surface 5a of the substrate and a second surface 32b in contact with the lower surface 35a of the first covering layer 35. In other words, in the cross-sectional view shown in FIG. 5, the first wiring layer 32 may be formed in a U-shape so that both end surfaces (open end surfaces) in the X direction are exposed, and the first covering layer 35 may be formed in the recesses of the first wiring layer 32.

[0048] In this manner, by configuring the first wiring layer 32 to be exposed on the surface, electrical continuity can be established between the upper surface 5 a of the substrate 5 and the first wiring layer 32 without the electrode 25 being interposed therebetween.

[0049] The above-described embodiments and modifications can be combined as appropriate, and new embodiments can be created by combining them. For example, in FIG. 5, instead of the first coating layer 35, the second wiring layer 36 described in FIG. 4 can be formed in the recess of the first wiring layer 32, and the same effect can be obtained. That is, it is possible to accommodate various resistance values ​​while keeping the cross-sectional area of ​​the heating wire 24 the same. In addition, electrical continuity with the first wiring layer 32 can be achieved from the substrate surface without passing through the electrode 25.

[0050] <Summary> A transparent heater 1 according to one embodiment of the present disclosure includes a transparent substrate 5 having a first groove 8 extending linearly and having a bottom formed on its upper surface, and a first wiring layer 32 having conductivity and embedded in the first groove 8, wherein the first wiring layer 32 contains impurities.

[0051] According to the above embodiment, the resistance value can be controlled by adjusting the impurity concentration of the first wiring layer 32 without changing the wiring width or thickness of the first wiring layer 32. This eliminates the need to narrow the wiring width or length of the first wiring layer 32, preventing a decrease in reliability due to high resistance. Furthermore, since the first wiring layer is embedded in the groove, only one side of the first wiring layer 32 is exposed, making it less likely that the chemical resistance and corrosion resistance will decrease due to the inclusion of impurities. Furthermore, protection such as passivation is also facilitated. The impurities may include, for example, carbon atoms or sulfur atoms.

[0052] In the above embodiment, a first covering layer 35 may be included which is laminated above the first wiring layer 32. By providing the first covering layer 35 in this manner, the chemical resistance and corrosion resistance of the first wiring layer 32 can be improved.

[0053] In the above embodiment, the reflectance of the first covering layer 35 to visible light wavelengths may be lower than the reflectance of the first wiring layer 32 to visible light wavelengths. This makes the first conductive wires 24 less visible when viewed from above. In the above embodiment, the resistivity of the first covering layer 35 may be higher than the resistivity of the first wiring layer.

[0054] The above embodiment may further include a second wiring layer 36 embedded in the first groove portion 8 and stacked above the first wiring layer 32, and the resistivity of the second wiring layer 36 may be higher than that of the first wiring layer 32. This allows for more precise control of the resistance value compared to when the wiring layer has a single-layer structure. In other words, it is possible to accommodate various resistance values ​​while keeping the cross-sectional area of ​​the heating wire 24 the same.

[0055] In the above embodiment, the impurity concentration of the first wiring layer 32 may be gradually decreased from the top surface downward.

[0056] In the above embodiment, the upper surface of the first wiring layer 32 may include a first surface 32a exposed toward the surface of the substrate 5 and a second surface 32b in contact with the lower surface 35a of the first covering layer 35. This exposes the first wiring layer 32 to the surface, allowing electrical continuity between the upper surface 5a of the substrate 5 and the first wiring layer 32 without the electrode 25 being interposed therebetween. [Industrial Applicability]

[0057] The present disclosure is industrially applicable as a transparent heater. [Explanation of symbols]

[0058] 1 Transparent heater 5. Substrate 8 First groove (groove) 32 First wiring layer 32a Top surface of first wiring layer 32b Lower surface of the first wiring layer 35 First coating layer (coating layer) 35a Underside of coating layer 36 Second wiring layer

Claims

1. a transparent substrate having a linear groove with a bottom formed on its upper surface; a first wiring layer buried in the groove and having conductivity; The first wiring layer includes an impurity.

2. The transparent heater according to claim 1, The transparent heater, wherein the impurities include carbon atoms or sulfur atoms.

3. The transparent heater according to claim 1, A transparent heater including a covering layer laminated above the first wiring layer.

4. The transparent heater according to claim 3, A transparent heater, wherein the reflectance of the covering layer to visible light wavelengths is lower than the reflectance of the first wiring layer to visible light wavelengths.

5. The transparent heater according to claim 3, A transparent heater, wherein the resistivity of the covering layer is higher than the resistivity of the first wiring layer.

6. The transparent heater according to claim 1, a second wiring layer embedded in the groove and stacked above the first wiring layer; A transparent heater, wherein the resistivity of the second wiring layer is higher than the resistivity of the first wiring layer.

7. The transparent heater according to claim 1, The impurity concentration of the first wiring layer gradually decreases from the top surface to the bottom surface.

8. The transparent heater according to claim 5, A transparent heater, wherein the upper surface of the first wiring layer includes a first surface exposed toward the substrate surface and a second surface in contact with the lower surface of the cover layer.

9. The transparent heater according to claim 3, a second wiring layer that is embedded in the groove, has electrical conductivity, and is in contact with the covering layer; an upper surface of the first wiring layer includes a first surface in contact with the covering layer and a second surface in contact with a lower surface of the second wiring layer; A transparent heater, wherein the resistivity of the second wiring layer is higher than the resistivity of the first wiring layer.

10. The transparent heater according to claim 1, The resistivity of the first wiring layer is 1.68×10 －８ Transparent heater with a resistance higher than [Ω·m].

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