JP2003217348A - Conductive paste, manufacturing method therefor and light-transmissive touch panel using this - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a conductive paste and a light-transmissive touch panel using this in which the connection resistance at a boundary face of a conductive layer and an electrode is small in the light-transmissive touch panel used for operation, in various kinds of electronic instruments. <P>SOLUTION: The conductive paste is formed by dispersing an alloy of silver and indium or a compound in which indium is deposited on silver in a synthetic resin and making the ratio of indium against the silver to 1-50 wt.%. Thereby, since the electrode formed by the conductive paste containing the same indium as a constituent of the conductive layer has good affinity for the boundary face of the conductive layer made of indium oxide tin, the conductive paste can be obtained in which the connection resistance at the boundary face of the upper conductive layer 6 and the upper electrode 17 and the connection resistance of the boundary face of the lower conductive layer 2 and the lower electrode 13 and a whole resistance value of the upper electrode 17 and the lower electrode 13 can be made small. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive paste, a method for manufacturing the same, and a light-transmitting touch panel using the same.

[0002]

2. Description of the Related Art In recent years, as electronic equipment has become more sophisticated and diversified, a light transmissive touch panel is mounted on the front surface of a display element such as an LCD, and characters displayed on the display element through the light transmissive touch panel. Increasingly, the functions and functions of the device are switched by visually recognizing and selecting symbols, symbols, pictures, etc. and operating the light-transmissive touch panel.

Such a conventional light transmissive touch panel will be described with reference to FIG.

FIG. 2 is a sectional view of a conventional light transmissive touch panel. In FIG. 2, reference numeral 1 denotes a light transmissive lower substrate, and a light transmissive lower conductive layer of indium tin oxide is provided on the upper surface of the lower substrate 1. 2 is formed.

On the upper surface of the lower conductive layer 2, lower electrodes 3 made of a conductive paste in which silver is dispersed in a synthetic resin are formed at both ends, and a lower light-transmitting conductive wiring board 4 is formed.
Is configured.

Reference numeral 5 is an optically transparent upper substrate, and an upper conductive layer 6 similar to the lower conductive layer 2 is formed on the lower surface of the upper substrate 5.

On the lower surface of the upper conductive layer 6, upper electrodes 7 made of a conductive paste similar to the lower electrode 3 are formed on both ends of the lower electrode 3 in a direction orthogonal to each other. The wiring board 8 is configured.

Further, the lower light-transmissive conductive wiring board 4 and the upper light-transmissive conductive wiring board 8 are provided with a frame-like spacer 9 whose upper and lower surfaces are coated with an adhesive (not shown). The light-transmitting touch panel is configured by bonding the outer periphery of the lower conductive layer 2 on the upper surface of the conductive wiring substrate 4 and the upper conductive layer 6 on the lower surface of the upper light-transmitting conductive wiring substrate 8 so as to face each other with a predetermined gap. ing.

In the above structure, the upper electrode 7 and the lower electrode 3
Is connected to the detection circuit of the electronic device, and a portion excluding the spacer 9 on the upper surface of the upper substrate 1, that is, an operation effective area where the pressing operation and its position can be detected is pressed with a finger or a pen, the upper substrate 1 The upper conductive layer 6 that is bent and pressed contacts the lower conductive layer 2, and the pressed position is detected by the resistance ratio between the upper electrodes 7 and between the lower electrodes 3.

[0010]

However, in the above-mentioned conventional conductive paste and the light transmissive touch panel using the same, the affinity between the material of the upper and lower conductive layers, indium tin oxide, and the material of the upper and lower electrodes, silver, is high. Since it was not so good, there was a problem that the connection resistance at the interfaces between the upper conductive layer 6 and the upper electrode 7 and between the lower conductive layer 2 and the lower electrode 3 was large.

SUMMARY OF THE INVENTION The present invention is intended to solve such a conventional problem, and an object thereof is to provide a conductive paste having a small connection resistance at the interface between a conductive layer and an electrode, and a light transmissive touch panel using the same. .

[0012]

In order to achieve the above object, the present invention has the following constitution.

According to the first aspect of the present invention, an alloy of silver and indium or a mixture of silver and indium deposited on a synthetic resin is dispersed, and the ratio of indium to silver is 1 to 50% by weight. The conductive paste is formed as, and the electrode formed of the conductive paste containing the same indium as the constituent of the conductive layer has a good affinity for the interface with the conductive layer made of indium tin oxide. This has the effect of making it possible to obtain a conductive paste that can reduce the connection resistance at the interface between the layer and the electrode and also reduce the resistance value of the entire electrode.

According to a second aspect of the present invention, silver and indium powder are stirred to deposit indium on the silver.
This is a method for producing the conductive paste described above, and has an effect that indium can be easily attached to silver.

According to a third aspect of the present invention, there is provided an upper substrate having an upper conductive layer formed on a lower surface thereof, and a lower substrate having a lower conductive layer formed on the upper surface thereof and facing the upper conductive layer with a predetermined gap therebetween. A light-transmissive touch panel having electrodes formed on the surface of at least one of an upper conductive layer and a lower conductive layer by the conductive paste according to claim 1, which has a small connection resistance and a small detection error. It has the effect that

According to a fourth aspect of the invention, in the third aspect of the invention, a predetermined electrode is formed by printing a conductive paste on the surface of the conductive layer and then drying at 150 to 250 ° C. Indium is much softer than silver and rich in malleability and has a melting point of 156 ° C.
When dried at 50 ° C., the indium contained in the conductive paste starts to melt from the surface and spreads to the interface between the conductive layer and the electrode to further reduce the connection resistance.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to FIG.

The same components as those described in the section of the prior art are designated by the same reference numerals to simplify the detailed description.

(Embodiment) FIG. 1 is a cross-sectional view of a light-transmitting touch panel according to an embodiment of the present invention. In FIG. 1, reference numeral 1 is a light-transmitting lower substrate such as glass or acrylic or polycarbonate resin. A light-transmitting lower conductive layer 2 of indium tin oxide is formed on the upper surface of the lower substrate 1.

Then, an alloy of silver and indium or a mixture of silver and indium adhered in a synthetic resin is dispersed, and a lower electrode formed of a conductive paste in which the ratio of indium to silver is 1 to 50% by weight. Thirteen
Are formed on both ends of the upper surface of the lower conductive layer 2 to form the lower light-transmissive conductive wiring board 14.

Reference numeral 5 is a light-transmissive upper substrate such as polyethylene terephthalate or polycarbonate film, and an upper conductive layer 6 similar to the lower conductive layer 2 is formed on the lower surface of the upper substrate 5.

Then, on the lower surface of the upper conductive layer 6, an upper electrode 17 formed of the same conductive paste as the lower electrode 13 is formed.
Are formed on both ends which are orthogonal to the lower electrode 13 to form an upper light-transmissive conductive wiring board 18.

The lower light-transmissive conductive wiring board 14 is also used.
The upper light-transmitting conductive wiring board 18 is formed by a frame-shaped spacer 9 such as a non-woven fabric or a polyester film whose upper and lower surfaces are coated with an adhesive (not shown) made of a thermoplastic resin such as an acrylic resin or a polyester resin. The lower conductive layer 2 on the upper surface of the lower light-transmissive conductive wiring board 14 and the upper conductive layer 6 on the lower surface of the upper light-transmissive conductive wiring board 18 are bonded together at their outer peripheries so as to face each other with a predetermined gap therebetween, thereby transmitting light. A sex touch panel is configured.

In the above-mentioned structure, the upper electrode 17 and the lower electrode 13 are connected to the detection circuit of the electronic device, and a position excluding the spacer 9 on the upper surface of the upper substrate 1, that is, an operation capable of pressing and detecting its position. When the effective area is pressed with a finger or a pen or the like, the upper substrate 1 bends, the upper conductive layer 6 contacts the lower conductive layer 2 at the pressed position, and the resistance ratio between the upper electrodes 17 and the lower electrodes 13 causes It is configured to detect the pressed position.

Next, a specific method of producing such a conductive paste and a method of forming electrodes using the same will be described.

First, a predetermined amount of silver powder (A, manufactured by Shoei Chemical Industry Co., Ltd.)
g530) and indium powder (Mitsui Kinzoku Co., Ltd.) were put into a ball pot mill, and a solvent solution of water: ethanol = 70: 30 and stearic acid of 0.01% were added to prevent coagulation.
Add by weight% and stir for 10 hours. After stirring, wash with methanol and dry.

Next, bisphenol resin (MR-1 manufactured by Showa Kasei Co., Ltd.) and ethylated rubitol were added to the dried product so that the paste viscosity was 10 Pa.s. s to give a conductive paste.

At this time, indium is 1 to 1 with respect to silver.
A 60 wt% ratio was prepared.

Then, this conductive paste is printed on the upper surfaces of the upper conductive layer 6 and the lower conductive layer 2 and then dried at 150 to 250 ° C. to form the upper electrode 17 and the lower electrode 13.

Since indium is much softer than silver and rich in spreadability, and has a melting point of 156 ° C.,
When dried at 0 to 250 ° C., the indium contained in the conductive paste begins to melt from the surface, spreads to the interface between the conductive layer and the electrode, and the connection resistance at this interface becomes smaller.

Next, a specific method for evaluating such a conductive paste will be described.

As described above, the conductive paste in which the ratio of indium to silver was changed was formed as the electrode on the upper surface of the conductive layer of indium tin oxide formed on the upper surface of the glass substrate. Was measured as the initial connection resistance value.

Next, the connection resistance value after 1000 cycles of a so-called thermal shock test, in which the test pieces were left at 85 ° C. for 30 minutes and at −30 ° C. for 30 minutes as one cycle, and a temperature of 6
The connection resistance value was measured after 1000 hours of so-called high temperature and high humidity test, in which the test piece was left to stand in 0 ° C. and 95% RH.

The results of this evaluation are shown in Table 1.

[0035]

[Table 1]

As is apparent from Table 1, No. 1 in which silver does not contain indium was used. No. 1 in which the ratio of indium to silver is 1 to 50% by weight as compared with No. 1. Nos. 2 to 6 had small initial connection resistance values and showed little change after thermal shock and after high temperature and high humidity.

The ratio of indium to silver is 60.
% By weight of No. No. 7 of 40% by weight or less. 1
The specific resistance, which is the reciprocal of the electric conductivity of the conductive paste, was about 10 times larger than that of Nos. 5 to 5, which was not preferable.

From the above, by setting the ratio of indium to silver to be 1 to 50% by weight, and more preferably 10 to 40% by weight, the connection resistance not only at the initial stage but also after thermal shock and after high temperature and high humidity can be obtained. A conductive paste having a small value and a small specific resistance can be obtained.

As described above, according to the present embodiment, the alloy of silver and indium or the one in which indium is attached to silver is dispersed in the synthetic resin, and the ratio of indium to silver is set to 1 to 50% by weight. By forming the conductive paste, the electrode formed of the conductive paste containing the same indium as the constituent component of the conductive layer has a good interface affinity with the conductive layer made of indium tin oxide. 6 and the upper electrode 17, and the lower conductive layer 2 and the lower electrode 1
The connection resistance at the interface of 3 can be reduced and the upper electrode 17
Also, it is possible to obtain a conductive paste that can reduce the resistance value of the entire lower electrode 13.

Further, indium can be easily attached to silver by stirring the silver and indium powders to produce a conductive paste.

Then, the upper conductivity of the upper substrate 5 having the lower conductive layer 6 formed on the lower surface and the lower substrate 1 having the lower conductive layer 2 facing the upper conductive layer 6 at a predetermined distance on the upper surface are formed. By forming the upper and lower electrodes 17 and 13 with the conductive paste on at least one of the surface of the layer 6 or the lower conductive layer 2 to form the light transparent touch panel, a light transparent touch panel having a small connection resistance and a small detection error is obtained. be able to.

Further, by printing a conductive paste on the surface of the conductive layer and drying at 150 to 250 ° C. to form a predetermined electrode, indium is much softer than silver and has a good spreadability and a melting point of 156 ° C. Therefore, 15
The indium contained in the conductive paste starts to melt from the surface during drying at 0 to 250 ° C., spreads to the interface between the conductive layer and the electrode, and the connection resistance can be further reduced.

In the above description, a conductive paste in which indium is adhered to silver is dispersed in a synthetic resin has been described. However, molten silver and molten indium are heated at temperatures above their respective melting points. The present invention can be practiced by using a mixture obtained by cooling the mixture obtained in (1) and cooling and solidifying the alloy of silver and indium in a synthetic resin.

[0044]

As described above, according to the present invention, by using indium having a good affinity for the conductive layer made of indium tin oxide in the conductive paste forming the electrode, the conductive layer-electrode interface can be formed. An advantageous effect that a conductive paste having a low connection resistance and a light transmissive touch panel using the same can be provided is obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a light transmissive touch panel according to an embodiment of the present invention.

FIG. 2 is a sectional view of a conventional light transmissive touch panel.

[Explanation of symbols]

1 Lower substrate 2 Lower conductive layer 3,13 Lower electrode 4,14 Lower light transmitting conductive wiring board 5 Upper substrate 6 Upper conductive layer 7,17 Upper electrode 8,18 Light-transmissive conductive wiring board 9 spacers

Continued front page    (72) Inventor Kenichi Takahata             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. F-term (reference) 5G006 AA01 AZ05 CD06 DD01 FB14                       FB19 FB30 FB39                 5G050 AA01 AA19 BA04 CA16 DA10                 5G301 DA02 DA03 DA42 DD01 DE01

Claims (4)

[Claims] 1. An alloy of silver and indium or a mixture of silver and indium adhered in a synthetic resin is dispersed, and the ratio of indium to silver is 1 to 50% by weight.
And conductive paste. 2. The method for producing a conductive paste according to claim 1, wherein the powder of silver and indium is stirred to deposit indium on the silver. 3. An upper substrate having an upper conductive layer formed on a lower surface,
2. An electrode formed by the conductive paste according to claim 1, comprising a lower substrate having a lower conductive layer formed on an upper surface thereof and facing the upper conductive layer with a predetermined space therebetween, and at least one of the upper conductive layer and the lower conductive layer surface. A light-transmissive touch panel. 4. The light transmissive touch panel according to claim 3, wherein a conductive paste is printed on the surface of the conductive layer and then dried at 150 to 250 ° C. to form a predetermined electrode.