JPH07186323A - Conductive film - Google Patents

Abstract

PURPOSE:To obtain a conductive film wherein a crease is difficult to be generated and its handling is easy by a method wherein a very thin film can be made by providing an organic polymeric material film formed in a metallic foil capable of being chemically etched, and a metallic film formed on the film. CONSTITUTION:A thermosetting polyimide resin film is formed on a metallic foil 1. Then, after a drying process, only its periphery part is exposed to light, subjected to development, and its periphery part is removed from the metallic foil 1. Thereafter, it is processed by thermosetting, and a film 2 consisting of thermosetting polyimide resin of 1-10mum thickness is formed on the metallic foil 1. Further, a metallic foil film is formed on the film to obtain a conductive film. Then, resist ink is printed on the metallic foil film. After removing a part other than the printed part with an etching agent, the resist ink is removed, and a pattern 3 for an electric circuit is formed. Further, an inside part on the metallic foil 1 side is removed by chemical etching, and only the periphery part forms the conductive film 4 of the metallic foil 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin conductive film which is easy to handle.

[0002]

2. Description of the Related Art Conventionally, a conductive film formed by forming a metal thin film on a substrate such as a plastic film has been widely used in various fields. At this time, a film generally used as a substrate is thick. It is said that a material having a stiffness of at least 25 μ is preferable. However,
For example, when it is used as a member for a sensor or the like, the base material needs to be thinned in order to increase its sensitivity, and there is a problem that the conventional one is too thick. Furthermore, a conductive film in which a metal thin film is directly formed on such a thin substrate is
There is a problem that wrinkles are generated on the film due to the action of heat when forming the metal thin film, and there is also a problem that handling is extremely difficult during post-processing such as fine processing and assembly processing. .

[0003]

In order to solve the above-mentioned problems, the inventors of the present invention have a thin metal film formed on a thin film and are useful in various fields such as sensor members and switch members. As a result of earnestly investigating such a conductive film, the present invention was finally achieved. An object of the present invention is to provide a conductive film having an excellent function as a sensor member, for example, a sensing unit such as a pressure sensor or a fingerprint sensor, and another object is to provide a touch switch component or the like. An object of the present invention is to provide a conductive film suitable as a switch member or the like.

Still another object is to provide a conductive film which is wrinkle resistant and easy to handle, although it is extremely thin, and yet another object is processing such as fine processing and assembly processing. It is to provide a conductive film that is easy to remove.

[0005]

The present invention has been made in view of the above objects, and is characterized by an organic polymer formed on a metal foil capable of chemical etching in a conductive film. The thin film has a structure including a material-based thin film and a metal thin film formed on the thin film. Further, the characteristic is that in the conductive film, the metal thin film is a pattern for an electric circuit. And / or a structure in which the peripheral portion of the metal foil is left and the other inner portions are removed by chemical etching.

Next, the means for solving the problems will be described in more detail. The metal foil according to the present invention is not particularly limited, but preferably copper, iron, aluminum, zinc, stainless steel and the like can be exemplified, and such a metal foil is bonded to an organic polymer material such as a polyimide resin. It has excellent properties and can be mentioned as a preferable example. The thickness is not particularly limited, but preferably 10 to 100 μm
More preferably, the thickness is about 30 to 80 μm, and the roll-formed one is more preferable.
Such a metal foil needs to be capable of being etched, and the chemical etching referred to in the present invention is a chemical etching method using a chemical agent or the like. Examples of the chemicals include corrosive inorganic acids and inorganic bases, such as nitric acid, hydrochloric acid, sulfuric acid, ferric chloride and ferric chloride.
Examples include copper, sodium hydroxide and potassium hydroxide. At the time of chemical etching, a paste or an aqueous solution of these corrosive compounds may be used, and any method may be used for etching. Such chemical etching removes at least a part of the metal foil in the conductive film according to the present invention. Since the conductive film is usually used in a cut state to suit each application, the place where the metal foil is to be removed by chemical etching should be the inside, and the peripheral part (frame part) should be left with the metal foil. It is more preferable to adopt such a configuration, and this configuration can be understood by referring to FIGS. 1 and 2. That is, in this figure, the metal foil 1 is present only in the peripheral frame portion, and in the inner portion (inside the broken line in FIG. 1), the metal foil is removed by etching. Thus
The metal foil 1 remaining in the frame portion has the effect of having the function of a support frame for the conductive film 4, and is more preferable.

The main purpose of using a metal foil is to facilitate the formation of an organic polymer material thin film. By forming an organic polymer material thin film using such a metal foil as a support, an extremely thin thin film can be formed. Molding is also possible.
The details of the forming method will be described later. It is needless to say that the conductive film of the present invention can be used as it is without removing the metal foil by chemical etching.

Next, the organic polymer material-based thin film in the present invention is a film-like thin film made of a synthetic resin such as a thermosetting resin or a thermoplastic resin, and has a thickness of 25 μm or less, preferably, 1 to 10 μm, more preferably 1 to
For example, it can be about 4 μm. A thin film having a thickness of more than 25 μm does not need a metal foil support, but when the rigidity is insufficient, a preferable thin film may not be formed without the metal foil support. Therefore, it goes without saying that the thickness value is not particularly limited. Examples of the synthetic resin described above include thermoplastic or thermosetting polyimide-based resins, polyether sulfone-based resins, polyarylate-based resins, polyester-based resins and the like, but are not particularly limited, but among others, thermosetting polyimide-based resins The resin is excellent in strength and heat resistance and can be exemplified as a preferable one.

The above-mentioned thermosetting polyimide-based resin is preferably used in the form of a polyimide-based precursor. For example, the above-mentioned precursor is used in the form of a liquid such as a varnish or a solution prepared by dissolving it in an organic solvent. In many cases. Since such a precursor liquid material can be cast on a metal foil to easily form a thin film, it is most easily used. Further, recently, photosensitive polyimide-based precursors have been available on the market, and the use of such a precursor has an advantage that post-processing is facilitated.

The method of forming the thin film is not particularly limited, but when the metal foil is thin, a method of coating the metal foil as a support by spin coating can be exemplified. The spin coating method is to supply a liquid material of an organic polymer material (including its precursor), such as a solution, a dispersion liquid, a varnish, etc., onto a metal foil arranged on a rotatable disk to move the disk at a predetermined speed. To form a thin film of the organic polymer material or its precursor, and then dry and heat it using an electric furnace if necessary to form a film-like thin film of the organic polymer material. There is also such a method. Depending on the type and thickness of the metal foil, a method of forming a thin film by an ordinary coating method such as a roll coater method can also be exemplified.

The metal thin film according to the present invention is formed on the above-mentioned organic polymer material-based thin film. The metal used here is not particularly limited, but specifically, gold, silver,
At least one of copper, platinum, titanium, nickel, tantalum, chromium, palladium, indium, tin, nichrome, iron and indium oxide, and indium-tin oxide (ITO) can be exemplified. At this time, the method of forming the metal thin film is not particularly limited, but specifically, a method of forming by a physical means such as a sputtering method, an ion plating method, an evaporation method, a method of forming by a plating means, or the like can be used. It can be illustrated. The thickness of the metal thin film thus formed is not particularly limited, but is preferably 0.01 to 20 μm.
m, and more preferably about 0.1 to 2 μm.

The metal thin film may be used as it is without being etched, or may be used by forming a pattern for electric circuit called patterning. Patterning is performed by removing a portion of the metal thin film other than the pattern forming portion by etching, but the pattern may be directly formed when the metal thin film is formed. At this time, the above-mentioned etching is usually performed by masking the preliminary pattern forming portion with an appropriate etching resistant agent and then treating with an etching agent such as HCl to remove the portion other than the pattern forming portion. . After that, when the masked anti-etching agent is removed, the removed portion becomes a pattern for an electric circuit. Further, the patterning is performed by covering a portion other than the preliminary pattern forming portion with a metal mask or the like, then forming a metal thin film by various methods such as sputtering, and thus forming a portion other than the portion covered with the metal mask or the like. It is also possible to directly form a metal thin film pattern.
As described above, there is no particular limitation on the patterning.

The conductive film thus obtained may have various modes depending on the presence or absence of etching of the metal foil and / or the presence or absence of patterning of the metal thin film, and the applications may also differ depending on the respective modes. Next, its typical use will be described below.

Among the conductive films of the present invention, those for etching a metal foil and patterning a metal thin film are most typically used as a sensing part of a pressure sensor or the like. The thin film is not patterned and is used as a sensing part such as a fingerprint sensor and a main part such as a touch switch and a transparent touch switch. However, as described above, various uses of the present invention are conceivable and are not particularly limited, and a wide range of uses in all directions are expected. The configurations of the present invention have been described above by way of example, and the present invention is not limited to these items.

Next, examples of the present invention will be described.

【Example】

Example 1 Using a spin coater, a thickness of 30 μm was set on a rotating disk.
Of stainless steel foil, and a photosensitive polyimide precursor varnish (Toray Industries, Inc., Photo Nice UR-310)
0) is supplied to form a precursor thin film (thickness 2 μm), and then a drying process is performed, and only the peripheral portion is exposed and developed, and the peripheral portion is covered with metal (as shown in FIG. 1). (Stainless steel) Removed from foil 1. After that, a thermosetting treatment was performed to form a film-like thin film made of a thermosetting polyimide resin having a thickness of 1 μm on the metal foil 1. At this time, the metal foil and the thin film were in close contact with each other, and the interlayer strength thereof was sufficient.

Further, a 0.5 μm-thick copper thin film was formed on the thin film by a sputtering method to obtain a conductive film according to the present invention. Then, a resist ink (anti-etching agent) is screen-printed on the copper thin film, then showered with dilute hydrochloric acid (etching agent) to remove the portions other than the printed portion, and then the resist ink is removed. A pattern for an electric circuit was formed as indicated by 3 in 1. Further, the metal foil side is chemically etched with a solution of ferric chloride to remove the inner portion (inside the chain line portion in FIG. 1) as shown in FIG. 1, and only the peripheral portion (frame portion) is the metal foil. A conductive film 4 made of 1 was prepared. The conductive film thus obtained was extremely useful as a sensing part of a pressure sensor.

FIG. 1 shows a conductive film 4 which constitutes a sensing portion of a pressure sensor, and FIG. 2 is a sectional view taken along the line BB. The sensing unit 4 is composed of a metal foil 1, a polyimide resin thin film 2, and a metal thin film pattern 3 that form a frame. Both ends of the pattern 3 are connected to copper wires (not shown), and pressure is applied by a predetermined electric circuit. Can be used as a pressure sensor. Next, the operation of the sensing unit 4 of the pressure sensor obtained in the present invention will be described. That is, when pressure (arrow A) is applied to the film-like thin film made of polyimide resin, the resistance of the electric circuit pattern made of the copper thin film changes due to the bending due to the pressure, and the pressure is detected by detecting this change. To do. Therefore, it is preferable that the pattern 3 is a single pattern and has a narrow width and a longer length so that the resistance change can be taken out as large as possible.

Example 2 In the conductive film obtained in the same manner as in Example 1, a metal thin film was not patterned, and a conductive film 5 having a structure in which the metal thin film was left as it was was obtained. Next, the ceramic sheet 7 to which the carbon paste 6 is applied,
The conductive film 5 obtained above was assembled into a structure as shown in FIG. 3 via the spacer 8 so that the metal thin film 13 and the carbon paste-coated surface 6 faced each other to obtain a touch switch. This touch switch has a switch function by being electrically energized by the contact between the metal thin film 13 and the carbon paste coating surface 6, and the touch surface of the touch switch obtained in this example has an extremely thin structure. Therefore, it has a feature that even a fine contact can be detected and a contact error is unlikely to occur.

Example 3 Using the same conductive film as in Example 2, a fingerprint sensor as shown in FIG. 3 was prepared. In this fingerprint sensor, a conductive film 15 and a glass sheet 10 provided on a CCD area sensor (video camera sensor) 9 are arranged via a spacer 18, and at this time, the conductive film 15 is formed.
The polyimide resin thin film 2 is placed on the surface so as to be in direct contact with the fingerprint, and the metal thin film 13 and the glass sheet 10 face each other. Here, the glass sheet 10 is a support for the conductive film (sensing section) 15 and also for introducing the reflected light from the metal thin film 13 into the CCD area sensor (video camera sensor) 9. At this time, the method for detecting the fingerprint is not particularly limited, but is usually performed by the following process. That is,
Since the conductive film 15 of this example has an extremely thin structure, the film 15 itself becomes uneven along the unevenness of the fingerprint, and the light is uneven due to the metal thin film 13 in the uneven film 15. Reflected in a circular shape, and the reflected light is introduced into the CCD area sensor through the glass sheet, the CCD area sensor detects the reflected light with unevenness of the fingerprint, and the process with the computer (in addition, the image by CRT This may be done by the above process. At this time, it goes without saying that a beam slitter or the like may be used instead of the glass sheet 10.

In the fingerprint sensor of this example, since the sensing portion uses the ultrathin polyimide resin film thin film and the ultrathin metal thin film, the unevenness of the fingerprint can be sufficiently identified. Usually, the unevenness of a fingerprint is said to be about 50 μm, and an ultrathin sensing section is required to detect this unevenness, and this example is excellent for such purposes.

By the way, the conventional fingerprint sensor has a structure in which the fingerprint is detected by directly touching the surface of the glass sheet provided on the CCD area sensor. There was also a problem that the surface of the glass sheet caused a decrease in sensitivity due to the humidity of the fingertip, but in this example, once the unevenness of the fingerprint is sensed by the sensing unit,
Since the unevenness is detected by the CCD area sensor, even if a fingerprint trace remains on the thin film, a detection error will not occur when the fingerprint is detected next time. It does not cause sensitivity deterioration.

[0023]

EFFECT OF THE INVENTION Since the conductive film of the present invention forms an organic polymer material-based thin film by using a metal foil, it is possible to prepare an extremely thin thin film. Is especially remarkable. Further, in the present invention, the metal foil can be chemically etched so that only a predetermined shape, for example, only the peripheral portion (frame portion) is left, and by doing so, the metal foil can play the role of a support. ,
Further expansion of applications can be expected. In addition, such a structure is less likely to wrinkle, easy to handle, and easy to adapt to an automated line during assembly.

[Brief description of drawings]

FIG. 1 is a plan view showing a sensing unit of a pressure sensor using a conductive film according to the present invention.

FIG. 2 is a sectional view taken along line BB of FIG.

FIG. 3 is a cross-sectional view of a touch switch using the conductive film according to the present invention as a main component.

FIG. 4 is a cross-sectional view of a fingerprint sensor using the conductive film according to the present invention as a sensing unit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Metal foil 2 Film-like thin film of polyimide resin 3 Electric circuit pattern of metal thin film 4 Conductive film (sensing part of pressure sensor) 5 Conductive film (touch part of touch switch) 6 Carbon paste coating layer 7 Ceramic sheet 8, 18 Spacer 9 CCD area sensor 10 Glass sheet 13 Metal thin film 15 Conductive film (sensing part of fingerprint sensor)

Claims (6)

[Claims] 1. A conductive film having a structure including an organic polymer material-based thin film formed on a metal foil capable of chemical etching, and a metal thin film formed on the thin film. 2. The conductive film according to claim 1, wherein at least a part of the metal foil is removed by chemical etching. 3. The conductive film according to claim 1, which has a configuration in which the peripheral portion of the metal foil is left and the other inner portions are removed by chemical etching. 4. The conductive film according to claim 1, wherein the metal thin film forms a pattern for an electric circuit. 5. The conductive film according to claim 1, wherein the organic polymer material-based thin film is a heat-effective polyimide-based resin thin film. 6. The organic polymer material thin film has a thickness of 1-10.
The conductive film according to claim 1, wherein the conductive film has a thickness of μm.