JP2000260231A - Film with conductive thin film and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a film without employing a complicated process such as lithography or etching, to remarkably simplify its process, and to reduce its manufacturing cost by providing multiple linear conductive film wiring patterns formed on one surface or both surfaces of a film-like insulating base material and separated from one another by cracks. SOLUTION: When a material having a thin film/base material structure is pulled in one direction, both the thin film 1 and the base material 2 extend to the same extent until the pulling reaches the tensile critical strain of the thin film 1, and when the strain due to the pulling reaches the critical value of the thin film 1, cracks 3 perpendicular to the pulling direction are produced in only the thin film 1. When the pulling is further continued, the thin film 1 is pulled through shearing stress on their interface, provided that the adhesion between the thin film and the base material remains, and more cracks 3 are produced almost evenly in the surface of the thin film, and the thin film 1 is brought into a form where elongated strip-like elements are continuously arranged, so that multiple linear conductive thin film wiring patterns are formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a finely divided linear conductive thin film / substrate system in general. Although the range of the thickness of the conductive thin film and the thickness of the base material may vary, the present invention is not particularly limited by the thickness.

[0002]

2. Description of the Related Art In recent years, conductive thin film materials have been widely used throughout the industry. In particular, transparent conductive thin film materials
It is used as an electrode for driving a matrix of a liquid crystal display or the like, and the demand is rapidly increasing. FIG. 6 shows a cross section of a general liquid crystal display. In general, when used for a liquid crystal display, a transparent conductive thin film (hereinafter, referred to as a “conductive film”) 20 is formed on one surface of each of two glass plates 21 sandwiching a liquid crystal 22. . Recently, a plastic plate (film) may be used instead of a glass plate to reduce the weight and flexibility of the display itself. Also in this case, the conductive film is formed on one surface of each of the two plastic plates (films).

However, to be used as an electrode for driving a matrix of a display, an isotropic conductive film is initially formed by a very troublesome pattern etching as shown in FIG. Are processed into a row of electrically isolated elongated strips, each connected to a drive circuit. The processed conductive films (the attached glass plates) are arranged so as to be shifted from each other by 90 degrees as shown in FIG. 7B. Any display matrix element (i,
When a voltage is applied to j), a voltage is applied to the i-th strip-shaped element on one side and the j-th element on the other side.

That is, since a conductive film is usually formed uniformly and electrically isotropically, when it is used as an electrode of a display, processing steps such as lithography and pattern etching for subdividing it in one direction are required. Becomes
In fact, this process involves many ancillary processes such as masking and exposure to a photocurable resin for pattern formation before pattern etching, and each process requires high precision. Has become.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a method for forming a conductive thin film without a complicated process such as lithography and etching. An object of the present invention is to provide a film with a conductive thin film having electrical insulation between adjacent wirings by a simple method. According to the present invention, for example, a process for manufacturing a liquid crystal display is greatly simplified, and a significant reduction in manufacturing cost can be expected.

[0006]

Means provided by the present invention to solve the above problems are as follows.
Formed on one or both sides of a film-like insulating substrate,
This is a film with a conductive thin film provided with a plurality of linear conductive thin film wirings separated from each other by cracks.

According to a second aspect of the present invention, there is provided the film with a conductive thin film according to the first aspect, wherein the breaking strain of the film-like insulating substrate is larger than the breaking strain of the conductive thin film.

According to a third aspect of the present invention, there is provided the film with a conductive thin film according to the first or second aspect, wherein cracks in the conductive thin film are closed by a non-conductor.

According to a fourth aspect of the present invention, the conductive thin film comprises:
A film is formed on one or both sides of a film-like insulating substrate having a breaking strain larger than the breaking strain of the conductive thin film to form a material, and the material is pulled in one direction to generate a number of cracks perpendicular to the pulling direction. A method for producing a film with a conductive thin film, comprising forming a plurality of linear conductive thin film wirings separated into a plurality of lines.

According to a fifth aspect of the present invention, the material is pulled at least until the base material undergoes plastic deformation, and the one-way conductivity is maintained even after unloading. This is a method for producing a film with a thin film.

According to a sixth aspect of the present invention, the pulling of the material is stopped at least within the time that the conductive thin film causes a buckling breakdown, and the one-way conductivity is maintained even after unloading. A method for producing a film with a conductive thin film according to claim 5.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, in general, when a material having a two-layer structure composed of a thin film / substrate has a larger strain than that of a thin film, the thin film / substrate system is moved in one direction. The crack that occurs in the thin film when pulled is described.

FIGS. 1A and 1B are explanatory diagrams when a thin film / substrate material is pulled in one direction. FIG. 1A shows a case where the tension is equal to or less than the critical strain of the thin film 1, and FIG. Is the case. Both the thin film 1 and the base material 2 extend to the same degree as the tensile strain of the thin film 1, but when the strain reaches the critical value of the thin film 1, cracks are generated only in the thin film 1 at right angles to the pulling direction. When the film is further pulled, if the adhesion between the thin film and the substrate remains, the thin film 1 is pulled through the shear stress at the interface, further cracks 3 are generated almost uniformly on the thin film surface, and the thin film 1 is elongated in one direction. The shape elements are continuously arranged.

Next, the case of a conductive thin film / film (substrate) -like insulating substrate will be described. In general, the critical tensile strain of a conductive thin film is smaller than that of a film (substrate) -like insulating base material. A row of strip-shaped elements elongated in the direction. At this time, the resistance in the long side direction (perpendicular to the pulling direction) of the strip remains almost the same as before the film was destroyed, but since each strip element is electrically insulated by cracks, the resistance is initially low. A conductive thin film having an anisotropic conductivity has a large resistance value in a short side direction (tensile direction). Therefore, a row of strip-shaped elements elongated in one direction becomes wiring of a large number of linear conductive thin films. Thereby, the film (substrate) with a conductive thin film on which the conductive film is formed acts as a film (substrate) with a unidirectional transparent conductive thin film provided with a plurality of conductive thin film wirings processed into strip-shaped elements. Things,
It becomes an electrode that can directly drive a liquid crystal display or the like in a matrix.

[0015]

Next, examples of a film (plate) with a one-way transparent conductive thin film and a method of manufacturing the same according to the present invention will be described in more detail with reference to the drawings.

<Example 1> As a specific material, a PET (film) having a thickness of 100 μm was used as a film (plate) -like insulating base material, an ITO thin film was used as a conductive thin film, and the base material was formed using a winding film forming apparatus. A sample uniformly formed on one side was used as a sample. The thickness of the ITO thin film was 150 nm. I
Loresta AP (Mitsubishi Yuka) was used to measure the surface electric resistance of the TO film. As a result of measuring the surface electric resistance of the formed sample, a substantially constant value of 300Ω / □ was obtained in the in-plane direction of the film.

Next, the sample was set in a unidirectional tensile tester and pulled until a crack occurred in the ITO thin film (about 2.2%). FIG. 2 shows cracks generated in the ITO thin film at this time. It can be seen that the thin film is formed by arranging elongated strip-shaped elements in one direction due to cracks.
Subsequently, the sample was removed from the tester and unloaded, and the surface electric resistance was measured by a usual method. Loresta AP for measurement
(Mitsubishi Yuka) was used to measure the resistance value of the four terminals. The results are shown in FIG. The horizontal axis in the figure shows the deviation of the angle between the crack and the four-terminal probe. When the probe and the crack are parallel, the deviation is 0 degree. The vertical axis is a logarithmic value obtained by normalizing the measured resistance value with the resistance value at 0 degree without cracks. In the crack direction, the resistance value is not much different from the initial resistance value, but when the angle is slightly deviated therefrom, a sharp increase in resistance is shown, indicating that it has an extremely sharp one-way conductive characteristic. However,
In order to have such a sharp one-way conductive property, attention must be paid to the final tensile rate of the material. That is, in the case of the ITO / PET system used in this embodiment, about 1.0%
However, if the load is removed from the testing machine at this tensile rate and the load is removed, the crack is closed again due to the elasticity of the PET film, the conductivity is restored, and the one-way conductive property almost disappears. In other words, it is important that the substrate be pulled beyond the yield strain of the substrate so that the crack is not closed even after unloading, and the process is performed until the substrate undergoes plastic deformation. Since the yield strain of the PET film used in this example was about 2.0%, as described above, the sample pulled to about 2.2% maintained sharp one-way conductive properties even after unloading. .

Alternatively, when the substrate is not pulled until the substrate yields for other reasons, the film (plate) material with a transparent conductive thin film is pulled to a desired value, and then the film is not renewed on the thin film in the pulled state. Conductor coating,
A method of closing a crack with a nonconductor is effective. Further, although the residual strain is large, even when the material is used as a display electrode while being pulled, the crack is opened, so that the one-way conductive property is maintained.

As described above, the destruction of the thin film is as follows.
First, many crack-like fractures perpendicular to the tensile direction occur. When the tension is further continued, a large number of fractures are generated in parallel with the tensile direction. FIG. 4 shows a state in which these destructions have occurred. When the thin film and the base material are compressed by the Poisson effect in a direction perpendicular to the tensile direction, the thin film and the base material have different Poisson's ratios. )), And is referred to herein as buckling failure.

It is important to keep the final tensile ratio before the pack ring failure 5 because if the material is pulled until this failure occurs, the high conductivity properties in the direction of the crack 4 will be lost. Incidentally, even in the case of the material of this example, the initial buckling failure was observed at around 5% or more, and when the high tensile state was reached, an increase in the surface resistance in the crack direction was observed.

The present invention is also effective for materials other than the materials used in the present embodiment when the breaking strain of the substrate is larger than that of the thin film. It is also possible to form a conductive thin film on both surfaces of the base material to generate cracks and use them.

Example 2 Next, a liquid crystal display was produced using the one-way conductive film produced in Example 1. FIG. 5 is a conceptual diagram showing the display in a plane.
(A) is a conceptual plan view of the whole, and (b) is a conceptual plan view partially enlarged. Portions other than the unidirectional conductive film according to the present invention have the same structure as the conventional liquid crystal display shown in FIGS. 6 and 7, and the manufacturing method is also the same.

First, two unidirectional conductive films obtained in Example 1 were prepared for an upper electrode and a lower electrode. Thereafter, a driving upper electrode 8 and a lower electrode 7 were provided. Electrode 7,
In No. 8, a metal material was vapor-deposited on a film and provided by patterning, etching, or the like using a normal photolithography technique.
At this time, one or more cracks (for the upper electrode) 1
0 (for the lower electrode) 9 was prepared so that the electrodes were electrically insulated. Next, these films were attached to two glass plates (without conductivity) constituting a liquid crystal panel, respectively, and further, these two glass plates were attached by rotating them by 90 degrees with the upper electrode side facing upward. Was. At this time, the intersection of the strip-shaped thin film wires connected to the upper and lower electrodes becomes the display matrix element 6. Further, when attaching the glass, an alignment film was formed and aligned on the side corresponding to the inside between the two glasses in advance in the same manner as in a normal liquid crystal panel production method. Next, liquid crystal sealing and the like were performed to obtain a liquid crystal panel. This is converted to a simple matrix drive circuit for experiments (64 pixels * 64 pixels, 36d
pi) and the display was displayed. as a result,
A good matrix drive was observed with high precision as a liquid crystal display, confirming the usefulness of the present invention.

[0024]

According to the present invention, a film (plate) with a conductive thin film having isotropic conductivity at first is simply pulled in one direction without using a complicated process such as etching, and thus, the electrical conductivity is reduced. It is possible to produce a film (plate) with a unidirectional (transparent) conductive thin film by processing it into a row of strip-shaped elements that are elongated in one direction and isolated in one direction. This greatly simplifies the process of manufacturing a liquid crystal display, for example, and can greatly reduce manufacturing costs.

[Brief description of the drawings]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram of a thin film crack generated by unidirectional stretching of a thin film / substrate system material, (a) is an explanatory diagram when the tensile is equal to or less than the critical strain of the thin film, and (b) is a critical strain of the thin film. FIG.

FIG. 2: About 2.2% of ITO thin film / PET film sample
The top view showing the pattern of the crack which arose in the thin film after pulling.

FIG. 3 is a characteristic diagram showing in-plane anisotropy of surface electric resistance of an ITO / PET sample after being pulled by 2.2%.

FIG. 4 is a plan view showing a pattern of buckling destruction generated in the ITO thin film.

FIG. 5 is a conceptual diagram showing an example of matrix driving of a liquid crystal display using a film with a unidirectional transparent conductive thin film.

FIG. 6 is an explanatory diagram showing a concept of a general liquid crystal display in a cross section.

7A and 7B are explanatory diagrams showing general liquid crystal display electrodes and matrix driving thereof, wherein FIG. 7A is an explanatory diagram showing the relationship between a transparent conductive thin film, a substrate and liquid crystal, and FIG. Explanatory drawing showing a relationship.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Thin film 2 ... Base material 3 ... Crack 4 ... Crack 5 ... Buckling destruction 6 ... Display matrix element 7 ... Lower electrode for driving 8 ... Upper part for driving Electrode 9 Crack for lower electrode 10 Crack for upper electrode 20 Transparent conductive thin film 21 Glass plate (plastic film plate) 22 Liquid crystal

Claims (6)

[Claims] 1. A film with a conductive thin film formed on one or both surfaces of a film-like insulating substrate and provided with a plurality of linear conductive thin film wirings separated from each other by cracks. 2. The film with a conductive thin film according to claim 1, wherein the breaking strain of the film-like insulating substrate is larger than the breaking strain of the conductive thin film. 3. The film with a conductive thin film according to claim 1, wherein cracks in the conductive thin film are closed by a non-conductor. 4. A conductive thin film is formed on one or both sides of a film-like insulating base material having a breaking strain larger than the breaking strain of the conductive thin film, and the material is pulled in one direction. A method for producing a film with a conductive thin film, characterized in that a large number of cracks perpendicular to the thin film are generated, and a large number of linear conductive thin film wirings separated from each other are formed. 5. The method for producing a film with a conductive thin film according to claim 4, wherein the stretching of the material is performed at least until the substrate undergoes plastic deformation, and the unidirectional conductivity is maintained even after unloading. . 6. The method according to claim 4, wherein the pulling of the material is stopped at least within the time that the conductive thin film causes buckling breakage, and the unidirectional conductivity is maintained even after unloading. A method for producing a film with a conductive thin film.