JP7401378B2 - wiring prints - Google Patents

Description

TECHNICAL FIELD The present invention relates to a printed circuit including a base material and a conductive layer.

BACKGROUND ART In recent years, wiring printed matter in which wiring made of a conductive layer is provided by printing on a base material made of an easily deformable film or sheet has come to be widely used. This type of wiring printed material has the advantage that it is inexpensive and that the base material can be deformed to match the shape of the object on which the wiring printed material is provided. In particular, by making it possible to attach the back side of the base material to the surface on which the wiring is provided to an object via an adhesive such as a pressure-sensitive adhesive, convenience becomes excellent.

When the base material is deformed, the wiring is also inevitably deformed. Since the wiring is relatively hard, cracks may occur in the wiring during this deformation. In this case, electrical conduction becomes difficult to occur in the cracks, so the resistance of the wiring increases. In order to avoid this, Patent Document 1 proposes making the curved portion of the wiring thicker so that cracks are less likely to occur.

JP 2017-5032 Publication

The conductive layer is generally applied to the substrate by known printing techniques such as inkjet printing or screen printing using a conductive paste. Therefore, in order to locally increase the thickness of the wiring, it is necessary to repeat printing. Therefore, it takes a long time. Furthermore, since there is a limit to the thickness that can be achieved by printing, there is also the problem that it is not easy to ensure a sufficient thickness for a portion of the conductive layer.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a wiring printed material that can avoid cracks in the conductive layer as much as possible.

In order to achieve the above object, according to one embodiment of the present invention, in a wiring printed material including a base material and wiring made of a conductive layer,
a first insulating layer formed on the base material;
the conductive layer formed on the first insulating layer;
a second insulating layer covering the conductive layer together with the first insulating layer;
Equipped with
The conductive layer is formed using a conductive paste containing conductive flakes and a binder that joins the conductive flakes as a starting material,
A wiring printed material is provided in which the bonding strength of the first insulating layer and the second insulating layer to the conductive layer is greater than the yield stress of the base material.

Further, according to another embodiment of the present invention, in a wiring printed material including a base material and wiring made of a conductive layer, and in which a curved part is formed,
a first insulating layer formed on the base material;
the conductive layer formed on the first insulating layer;
a second insulating layer covering the conductive layer together with the first insulating layer;
Equipped with
The conductive layer is formed using a conductive paste containing conductive flakes and a binder that joins the conductive flakes as a starting material,
The softening temperature of the conductive paste is lower than that of the base material, and the softening temperature of the base material is lower than the softening temperatures of the first insulating layer and the second insulating layer. A wiring print is provided.

According to the present invention, materials for the first insulating layer and the second insulating layer constituting the printed circuit are selected from materials whose bonding strength to the conductive layer is greater than the yield stress of the base material. Therefore, even when the base material undergoes plastic deformation, the conductive layer sandwiched between the first insulating layer and the second insulating layer remains bonded to both insulating layers. That is, the conductive layer is protected by both insulating layers covering the conductive layer. For this reason, the state in which the conductive flakes in the conductive layer are bonded via the binder is maintained, thereby suppressing the occurrence of cracks in the conductive layer.

Alternatively, a conductive paste containing conductive flakes and a binder for bonding the conductive flakes is selected as the starting material for the conductive layer constituting the wiring printed material. Further, the softening temperatures of the conductive paste, the base material, the first insulating layer, and the second insulating layer become high in this order. In this case, when obtaining a wiring print, the conductive paste is protected by the first insulating layer and the second insulating layer and deforms together with the base material to follow the shape of the object to be pasted. That is, the wiring printed material has good shape followability. For this reason, the state in which the conductive flakes are bonded via the binder is maintained, so that the occurrence of cracks in the conductive layer 16 is suppressed.

FIG. 2 is an overall schematic perspective view of the first wiring printed material according to the first embodiment of the present invention attached to a first attachment target. FIG. 2 is a schematic side view of the main part of FIG. 1; 2 is a sectional view taken along the line III-III in FIG. 1. FIG. FIGS. 4A and 4B are a schematic flowchart of attaching the first wiring printed material to the columnar convex portion. FIG. 7 is an overall schematic perspective view of a second wiring printed product according to a second embodiment of the present invention attached to a second attachment target. FIG. 7 is a schematic side sectional view of the main part when joining the second printed circuit to the hemispherical convex portion of the second object to be pasted. It is a graph showing the relationship between the total thickness of the first insulating layer and the second insulating layer and the resistance of the second wiring printed material.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the wiring printed matter according to the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is an overall schematic perspective view of a first wiring printed material 10 according to the first embodiment. This first wiring printed material 10 is pasted on the first pasting object 12 . Here, the first attachment target 12 has a columnar convex portion 14 that protrudes vertically upward from the upper end surface of the flat plate-shaped portion 13. As shown in FIGS. 1 and 2, the first wiring printed material 10 is attached so as to go over the columnar convex portion 14. As shown in FIGS.

FIG. 3 is a sectional view taken along the line III-III in FIG. In addition, in FIG. 3, the first pasting object 12 is omitted and only the first wiring printed material 10 is shown. Furthermore, in order to facilitate understanding of the conductive flakes 18 and binder 20 that constitute the conductive layer 16, they are shown simply and schematically, and the actual scale is ignored.

The first wiring printed material 10 includes a base material 22, a first insulating layer 24, a conductive layer 16 (or wiring), and a second insulating layer 26 in this order from the side close to the object to be pasted. The starting material of the base material 22 is selected and its thickness is set so that it exhibits excellent flexibility and is easily deformed. A suitable example of the starting material for the base material 22 is polyethylene terephthalate (PET). When a seal-like base material is used, it may be a releasable PET. Further, an adhesive such as a pressure-sensitive adhesive is applied to the end surface of the base material 22 facing the first attachment target 12, and a protective sheet (none of which is shown) for protecting the adhesive is applied. It will be pasted.

The first insulating layer 24 and the second insulating layer 26 have the conductive layer 16 interposed therebetween in areas where the conductive layer 16 exists, and are integrated in areas where the conductive layer 16 does not exist. In other words, the first insulating layer 24 and the second insulating layer 26 cover the conductive layer 16. In addition, in FIG. 3, a boundary line is attached to distinguish the first insulating layer 24 and the second insulating layer 26, which are printed separately in separate steps, but the boundaries between the first insulating layer 24 and the second insulating layer 26 are There is no particular need for a clear boundary line (interface) to exist between them. Furthermore, the first insulating layer 24 and the second insulating layer 26 are, for example, transparent.

The first insulating layer 24 and the second insulating layer 26 are made of a soft insulating material. Suitable starting materials for the first insulating layer 24 and the second insulating layer 26 include insulating polymers such as polycarbonate.

The conductive layer 16 (wiring) is spaced apart from the base material 22 by the thickness of the first insulating layer 24 . Further, the wiring is mainly protected by the second insulating layer 26 provided directly above the conductive layer 16. In this case, the conductive layer 16 is formed using a conductive paste containing conductive flakes 18 and a binder 20 as a starting material. A suitable example of this type of conductive paste is silver (Ag) paste, which is easily available and relatively inexpensive.

In the above configuration, the bonding strength of the first insulating layer 24 and the second insulating layer 26 to the conductive layer 16 is greater than the yield stress of the base material 22, that is, the stress that exceeds the elastic deformation region and reaches the plastic deformation region. It is set to large. This means that when the base material 22 undergoes plastic deformation, the first insulating layer 24 and the second insulating layer 26 are bonded to the conductive layer 16 without coming off.

The first wiring printed material 10 according to the first embodiment is basically configured as described above, and its effects will be explained next.

In order to attach the first wiring printed material 10 to the first attachment target 12, first, the protective sheet is peeled off from the back surface of the base material 22. This exposes the adhesive, so turn the back side of the base material 22 toward the first object 12 and press a part of the back surface of the base material 22 onto the top surface of the first object 12, as shown in FIG. 4A. guess. As a result, the part of the back surface is pasted onto the top surface of the first pasting object 12. Thereafter, the back surface of the base material 22 is sequentially pressed against the columnar convex portion 14 from the side away from it to the side closer to it.

At the locations where the columnar protrusions 14 are provided, the first wiring printed material 10 rides on the columnar protrusions 14, as shown in FIGS. 4B and 2. That is, the first wiring printed material 10 is attached to one side, the top surface, and the other side of the columnar convex portion 14 in this order. In this process, the first wiring printed material 10 includes a boundary between the flat plate-shaped portion 13 and one side of the columnar projection 14, a boundary between one side of the columnar projection 14 and the top surface, and a boundary between the top surface and the columnar projection 14. A bent portion 28 (curved portion) as a plastically deformed portion is formed at the boundary with the other side surface and the boundary between the other side surface of the columnar convex portion 14 and the flat plate-shaped portion 13.

Here, when the resistance value of the printed wiring according to the prior art in which the first insulating layer 24 and the second insulating layer 26 are not formed is measured, it is approximately 2.5 times the resistance value of the first printed wiring 10. The reason for this is thought to be that in the wiring printed matter according to the prior art, cracks occurred in the conductive layer 16 at the bent portions 28 as described above, and the resistance of the wiring increased.

In contrast, in the first embodiment, the bonding strength of the first insulating layer 24 and the second insulating layer 26 to the conductive layer 16 is greater than the yield stress of the base material 22. Therefore, the state in which the conductive layer 16 is bonded to the first insulating layer 24 and the second insulating layer 26 is maintained at the bent portion 28 . That is, the conductive layer 16 is protected by the first insulating layer 24 and the second insulating layer 26, thereby maintaining the state in which the conductive flakes 18 are bonded via the binder 20. Therefore, generation of cracks in the conductive layer 16 (wiring) is suppressed.

As a result, the resistance of the wiring is prevented from increasing. That is, according to the first embodiment, it is possible to configure the first wiring printed material 10 in which the wiring exhibits sufficient conductivity. Moreover, in this case, there is no particular need to increase the thickness of the portion of the conductive layer 16 that corresponds to the bent portion 28. Therefore, the first wiring printed material 10 can be obtained efficiently in a relatively short time.

In order to obtain the first wiring printed material 10, the first insulating layer 24, the conductive layer 16, and the second insulating layer 26 may be individually formed in this order on the base material 22. As mentioned above, suitable examples of starting materials for the base material 22, the first insulating layer 24 and the second insulating layer 26, and the conductive layer 16 include PET (or release PET), polycarbonate, and silver paste (silver flakes and binder 20 and a mixture of solvents). Further, the first insulating layer 24, the conductive layer 16, and the second insulating layer 26 are preferably formed by inkjet printing.

Next, the second wiring printed material 30 according to the second embodiment shown in FIG. 5 will be explained. This second wiring printed material 30 is joined to the second attachment object 32 by welding. Here, the second pasting object 32 has a hemispherical convex portion 34 that bulges out in a hemispherical shape from the upper end surface of the flat plate-shaped portion 13. The second wiring printed material 30 is bonded over the entire one end surface of the second attachment target 32 so as to cover the hemispherical convex portion 34 .

Similar to the first wiring printed material 10, the second wiring printed material 30 includes the base material 22, the first insulating layer 24, the conductive layer 16, and the second insulating layer 26 in this order from the side close to the second attachment target 32. (See Figure 3). Therefore, detailed description of each layer will be omitted.

In the second wiring printed material 30, starting materials for the base material 22, the first and second insulating layers 24 and 26, and the conductive layer 16 are selected from materials whose softening temperatures satisfy a predetermined relationship. Specifically, the conductive paste has the lowest softening temperature, the first insulating layer 24 and the second insulating layer 26 have the highest softening temperature, and the base material 22 has a softening temperature between them. That is, regarding the level of softening temperature, the following relational expression holds true.
Conductive paste<base material 22<first insulating layer 24 and second insulating layer 26

Note that the softening temperature of the conductive paste and the base material 22 is the glass transition point. Further, the softening temperature of the first insulating layer 24 and the second insulating layer 26 refers to the deflection temperature under load, but the value indicated by the manufacturer of the first insulating layer 24 and the second insulating layer 26 as the nominal value of "heat-resistant temperature" is You may also use it. Examples of starting materials for the base material 22, the first insulating layer 24, the second insulating layer 26, and the conductive layer 16 that satisfy the above relational expression include PET (or release PET), polyurethane, and silver paste, respectively.

The second wiring printed material 30 according to the second embodiment is basically configured as described above, and its effects will be explained next.

In order to join the second wiring printed material 30 to the second attachment target 32, first, the second wiring printed material 30 is heated. This heating is preferably performed from the base material 22 side. Further, at this time, heat is applied to an extent that exceeds the softening temperature of the conductive paste and the base material 22. Thereby, the conductive paste and the base material 22 are sufficiently softened.

Next, the second wiring printed material 30 whose conductive paste and base material 22 have been softened by heating is placed on one end surface of the second pasting object 32 . At this time, as shown in FIG. 6, the second wiring printed material 30 is stretched so as to be inclined from the flat plate-shaped part 13 of the second pasting object 32 to the top of the hemispherical convex part 34. Therefore, at this point, a closed space 40 is formed between the second wiring printed material 30 and the vicinity of the boundary between the flat plate-shaped portion 13 and the hemispherical convex portion 34 of the second attachment target 32 .

Next, the gas in the closed space 40 is sucked by a suction mechanism such as a pump (not shown) and is discharged outside the closed space 40 . As a result, the inside of the closed space 40 becomes negative pressure, so that the portion of the second wiring printed material 30 that defines the closed space 40 approaches and abuts near the boundary between the flat plate-shaped portion 13 and the hemispherical convex portion 34. . When the temperature of the second wiring printed material 30 decreases in this state, the base material 22 becomes fixed to the second attachment target 32.

A curved portion 42 (curved portion) as a plastically deformed portion is formed at a portion of the second wiring printed material 30 corresponding to the vicinity of the boundary between the flat plate-shaped portion 13 and the hemispherical convex portion 34 . As described above, in the second embodiment, the softening temperature (heat resistance temperature) of the first insulating layer 24 and the second insulating layer 26 is higher than that of the base material 22 and the conductive paste. Therefore, the conductive paste deforms together with the base material 22, following the shape of the hemispherical convex portion 34 while being protected by the first insulating layer 24 and the second insulating layer 26. That is, the second wiring printed material 30 has good shape followability.

For the above reasons, the state in which the conductive flakes 18 are bonded via the binder 20 is maintained in the second wiring printed material 30 as well. Therefore, generation of cracks in the conductive layer 16 (wiring) is suppressed.

FIG. 7 is a graph showing the relationship between the total thickness of the first insulating layer 24 and the second insulating layer 26 and the resistance of the second wiring printed material 30. This graph shows that as the total thickness increases, the resistance decreases. That is, the state in which the conductive flakes 18 are bonded via the binder 20 is maintained appropriately.

In order to obtain the second wiring printed material 30, the first insulating layer 24, the conductive layer 16, and the second insulating layer 26 may be individually formed in this order on the base material 22. As mentioned above, suitable examples of starting materials for the base material 22, the first insulating layer 24 and the second insulating layer 26, and the conductive layer 16 include PET (or release PET), polycarbonate, and silver paste (silver flakes and binder 20 and a mixture of solvents). Further, the first insulating layer 24, the conductive layer 16, and the second insulating layer 26 are preferably formed by inkjet printing.

By performing the simple operation of pasting the first wiring printed material 10 and the second wiring printed material 30 obtained in this way onto the first pasting object 12 and the second pasting object 32, the user can place the first wiring printed material 10 and the second wiring printed material 30 at the desired location. Appropriate wiring can be provided for.

The present invention is not particularly limited to the embodiments described above, and various modifications can be made without departing from the spirit of the present invention.

For example, the first application object 12 may be provided with a curved projection such as the hemispherical projection 34, and the second application object 32 may be provided with a curved projection such as the columnar projection 14. You can.

DESCRIPTION OF SYMBOLS 10, 30... Wiring printed material 12, 32... Pasting object 14... Columnar convex part 16... Conductive layer 18... Conductive flake 20... Binder 22... Base material 24, 26... Insulating layer 28... Bent part 34... Hemispherical convex part 40...Closed space 42...Curved part

Claims (4)

In a wiring printed material including a base material and wiring made of a conductive layer,
a first insulating layer formed on the base material;
the conductive layer formed on the first insulating layer;
a second insulating layer covering the conductive layer together with the first insulating layer;
Equipped with
The conductive layer is formed using a conductive paste containing conductive flakes and a binder that joins the conductive flakes as a starting material,
A wiring printed material, wherein the bonding strength of the first insulating layer and the second insulating layer to the conductive layer is greater than the yield stress of the base material. 2. The wiring printed material according to claim 1, wherein the base material is polyethylene terephthalate, the conductive paste is silver paste, and the first insulating layer and the second insulating layer are polycarbonate. A wiring printed material including a base material and a wiring made of a conductive layer, and in which a curved portion is formed,
a first insulating layer formed on the base material;
the conductive layer formed on the first insulating layer;
a second insulating layer covering the conductive layer together with the first insulating layer;
Equipped with
The conductive layer is formed using a conductive paste containing conductive flakes and a binder that joins the conductive flakes as a starting material,
The softening temperature of the conductive paste is lower than that of the base material, and the softening temperature of the base material is lower than the softening temperatures of the first insulating layer and the second insulating layer. A wiring print. 4. The wiring printed material according to claim 3, wherein the base material is polyethylene terephthalate, the conductive paste is silver paste, and the first insulating layer and the second insulating layer are polyurethane.

Images