JP2003091367A - Touch panel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly reliable touch panel with a driving electrode having a less dispersed resistance value. SOLUTION: The resistance film type analog touch panel comprises a transparent electrode formed on an upper board and a transparent electrode formed on a lower board, both of which are opposed to each other in spaced relation, and the driving electrode connected to the transparent electrodes. The driving electrode is formed with a fired film of conductive paste consisting of a 30-45 wt.% silver powder 32 and 15-25 wt.% insulating auxiliary particles 30 mixed in a resin solution. The particle size of the silver powder 32 is within a range of 0.1-5 μm, and the insulating auxiliary particles 30 are plastic balls, ceramic balls or glass balls with their average particle size being within a range of 1-20 μm and satisfied with the conditions of 3-10 times the particle size of the silver powder 32.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in devices such as computers, various terminals, vending machines, and ATMs, which are arranged on the screen of a liquid crystal display, a cathode ray tube or the like, and the user can display information according to the instructions on the screen seen through. The present invention relates to a resistive film type analog touch panel in which data is input by directly pressing a display screen with a finger, a pen or the like, and particularly to a touch panel with highly reliable electrodes.

[0002]

2. Description of the Related Art A resistive film type analog touch panel as an input switch integrated with a display device is used by being arranged on a display surface of the display device. The touch panel is
An upper substrate composed of a transparent substrate and a transparent electrode formed on the lower surface thereof and a lower substrate composed of a transparent substrate and a transparent electrode formed on the upper surface of the transparent substrate face each other with a predetermined space therebetween. It is located in.

In this touch panel, when the upper portion of the upper substrate is pressed with an input pen or a finger, the upper substrate is bent and the transparent electrode of the upper substrate comes into contact with the transparent electrode of the lower substrate at the pressing point. Then, the coordinates of the contact point are detected by measuring the electric resistance, and the input information is read. Less than,
An example of a touch panel in the related art will be described with reference to the drawings.

As shown in FIG. 4, the conventional touch panel has a transparent electrode 16 formed on the upper substrate 11 on the touch side (input side) and a transparent electrode 19 formed on the lower substrate 12 having flexibility.
And are opposed to each other with a gap therebetween with an insulating bonding agent 13 interposed therebetween. In addition, the transparent electrode 16 of the upper substrate 11
A pair of parallel X-side drive electrodes 14 and 15 connected to
A pair of parallel Y-side drive electrodes 21 and 22 connected to the transparent electrode 19 of the lower substrate 12 are arranged to face each other in a square arrangement. Furthermore, connection electrodes 17 and 1 connected to the X-side drive electrodes 14 and 15 of the upper substrate 11, respectively.
Reference numeral 8 is connected to the connection electrodes 23 and 24 provided on the lower substrate 12 with a conductive adhesive, respectively. The lower substrate is usually made of transparent glass and the upper substrate is usually made of a transparent film.

The X-side drive electrodes 14 and 15 and the Y-side drive electrodes 21 and 22 were formed as low-resistance electrodes by printing silver paste on the upper substrate 11 and the lower substrate 12, respectively, and firing the paste. The silver paste is prepared by adding silver powder to a solution of an aging curable resin such as an epoxy resin or an acrylic resin.
It is prepared by mixing at a ratio of ~ 85% by weight. The particle size of the silver powder is generally 0.5 to 1.0 μm.

[0006]

However, when not only silver but also metal particles are immersed in a liquid, they naturally precipitate because of their specific gravity, but when they become fine particles of about 5 μm or less, they do not completely precipitate and they partially float. It becomes a state. This phenomenon becomes more remarkable as the viscosity of the liquid increases. Therefore, the metal fine particles are close to a diffusion state in the paste. However, the metal fine particles in the highly viscous liquid have the property that the metal particles attract each other, and it is considered that this property tends to cause the silver powder to agglomerate.
Precipitation occurs for some reason. In particular, since silver powder has a high specific gravity, it may precipitate in the resin solution before curing or may be scattered in the resin solution as a lump in which silver powders are accumulated. However, it is difficult to obtain stable conductivity.

Therefore, in order to ensure good conductivity of the electrode by the silver paste, it is necessary to increase the content of the silver powder in the resin solution, and as a result, it is preferable to use paste. In a state where it looks like a moist powder, it is difficult to print itself, which becomes an impediment to the uniformization of the film thickness of the formed drive electrode, and the resistance value after firing is 20 to 30%. The result was scattered. In this way, the principle of diffusing silver powder into the resin solution to form a conductor after curing is stochastic, and the idea is that somewhere silver powder is connected and electrical continuity is secured as a whole.
Therefore, the technique regarding uniform diffusion of silver powder in the conductive paste is an important position.

As a measure against the above problem, there is disclosed a method of avoiding the variation of the resistance value by increasing the printing width H of the electrode pattern or forming a thick print film. However, such a method has problems that the external dimensions of the touch panel are increased and the number of steps is increased.

(Object of the Invention) An object of the present invention is to solve the above-mentioned problems, to avoid variations in the resistance value of the drive electrodes, and to provide a highly reliable touch panel.

[0010]

In order to achieve the above-mentioned object, a touch panel according to a first aspect of the present invention comprises a transparent electrode formed on an upper substrate and a transparent electrode formed on a lower substrate. In a touch panel having a driving electrode connected to each of the transparent electrodes, which is arranged to face each other with a gap,
The drive electrode is formed of a fired film of a conductive paste in which a resin solution is mixed with 30 to 45% by weight of silver powder and 15 to 25% by weight of spherical auxiliary particles.
The spherical auxiliary particles are in the range of 1 to 5 μm, the average particle size of the spherical auxiliary particles is in the range of 1 to 20 μm, and 3 to 10 times the particle size of the silver powder is satisfied.

The touch panel according to the second aspect of the present invention is the touch panel according to the first aspect, wherein when the average particle size of the spherical auxiliary particles is 1 to less than 5 μm, the variation in particle size is caused. The average particle size is 30% or less, and when the average particle size is 5 to 20 μm, the variation in particle size is 50% or less of the average particle size.

The touch panel according to claim 3 of the present invention is the touch panel according to claim 1 or 2, wherein the spherical auxiliary particles are plastic balls.
It is characterized by being made of insulating auxiliary particles such as glass spheres or ceramic spheres.

Further, in the touch panel according to the invention of claim 4 of the present invention, in the touch panel according to claim 1 or 2, the spherical auxiliary particles have a conductive property obtained by coating the insulating auxiliary particles with a conductive film. It is characterized in that it is composed of sex auxiliary grains.

The touch panel according to claim 5 of the present invention is the touch panel according to claim 4, wherein the conductive film has a thickness of 0.05 to 0.2 μm. The touch panel according to item 4.

The touch panel according to claim 6 of the present invention is the touch panel according to claim 4 or 5, wherein the conductive film is gold.

The touch panel according to claim 7 of the present invention is the touch panel according to claim 1, wherein the drive electrode pattern is formed by using the conductive paste by printing.

(Function) In the conductive paste for the touch panel of the present invention, the insulating auxiliary particles such as ceramic spheres, glass spheres, or plastic spheres having a size larger than the silver powder are dispersed in the resin solution together with the silver powder. The silver powder is distributed around the insulating auxiliary particles. As a result, it is possible to suppress the occurrence of the situation in which silver powder is accumulated in the conductive paste as lumps and scattered in the resin solution, and the silver powder is evenly diffused to obtain a drive electrode having stable conductivity. You can

Furthermore, more stable conductivity can be obtained by diffusing the conductive auxiliary particles obtained by coating the insulating auxiliary particles with the conductive film together with the silver powder in the resin solution, and driving the conductive film to be formed. Further improve the quality of the conductivity of the electrode. Hereinafter, the embodiments of the present invention will be described in detail.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) FIGS. 1 and 2
The first embodiment of the present invention will be described using. Figure 1
Is the Y-side drive electrode 4 of the touch panel in the present embodiment.
It is sectional drawing which shows a part of 2. Further, FIG. 2 is a partially enlarged view showing a diffusion state of the insulating auxiliary particles 30 and the silver powder 32 in the conductive paste in the present embodiment. The overall structure of the touch panel in this embodiment is the same as that of the conventional example, and thus the description thereof is omitted. This embodiment will be described below with reference to the drawings.

As shown in FIGS. 1 and 2, the Y-side drive electrode 42 of the touch panel according to the present embodiment is a mixture of the epoxy powder of the aging curable resin and the insulating auxiliary particles 30 as spherical auxiliary particles together with the silver powder 32. The conductive paste is printed on the lower substrate 12 and fired to form a low resistance electrode.

Silver powder 32 added to the conductive paste
Is set to 30 to 45% by weight before drying, which is about half that of the conventional method. In addition, the insulating auxiliary particles 30 whose particle size has been adjusted to some extent together with the silver powder 32 are contained in an amount of 15 to 25% by weight before drying.
Added. As the insulating auxiliary particles, plastic spheres, ceramic spheres, or glass spheres can be used. For example, the ceramic spheres include alumina (Al ₂ O ₃ ) and the glass spheres include silica glass (SiO).

Despite the difference in specific gravity between the ceramic sphere (specific gravity of about 1.9) and the silica glass (specific gravity of about 2.0) and the plastic sphere (specific gravity of about 1.0), there is no significant difference. It was not seen and the same effect was obtained.
It is considered that the reason is that when the ceramic sphere has a porous structure, the effective specific gravity is almost the same as that of the plastic sphere.

The insulating auxiliary particles 30 to be added may have a particle size of 1 to 20 μm, but in the present invention, the size is selected to be 3 to 10 times the particle size of the silver powder 32 to be added at the same time. Is important for getting the effect.

The variation in the outer diameter of the insulating auxiliary particles 30 to be added is such that the average particle diameter of the insulating auxiliary particles 30 is 1 to 5 μm.
When it is less than m, it is desirable to suppress the variation of the particle diameter to 30% or less of the average particle diameter, and when the average particle diameter is 5 to 20 μm, it is desirable to suppress the variation of the particle diameter to 50% or less of the average particle diameter.

In the present embodiment, the Y drive electrode has been described as an example, but it goes without saying that the same applies to the X drive electrode.

As described above, according to the present embodiment, the silver powder 32 is distributed around the insulating auxiliary particles 30 such as the ceramic spheres, the plastic spheres, or the glass spheres diffused in an appropriate state, thereby obtaining good conductive characteristics. I was able to. Further, since the insulating auxiliary particles 30 having a particle size larger than that of the silver powder 32 are appropriately diffused, it is possible to suppress the phenomenon that the silver powder 32 is accumulated. As a result, it was possible to reduce the variation in the resistance value to 5% or less when the geometrical dimensions (width H, thickness of the electrode) of the drive electrode were set to the same conditions as in the conventional method.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 3 is a partially enlarged view showing a contact state between the conductive auxiliary particles 33 as the spherical auxiliary particles in the conductive paste and the silver powder 32 in the present embodiment. Incidentally, regarding the same parts as those of the first embodiment,
The description is omitted. This embodiment will be described below with reference to the drawings.

As shown in FIG. 3, the first embodiment of the conductive paste of this embodiment is that the conductive auxiliary particles 33 as spherical auxiliary particles are mixed with the silver powder 32 in the epoxy resin solution of the aging curable resin. Unlike the form, the others are the same.

In this embodiment, the proportion of the silver powder 32 added to the conductive paste is set to 30 to 45% by weight, as in the first embodiment. In addition, the surface of the insulating auxiliary particles 30 whose particle size has been adjusted to some extent together with the silver powder 32 is coated with a conductive film 31 of gold by a method such as electroless plating to form conductive auxiliary particles 33 in a weight ratio before drying of 15- Add 25%.
The insulating auxiliary particles 30 may be plastic spheres, ceramic spheres, glass spheres or the like as in the first embodiment, and the particle size of the insulating auxiliary particles 30 to be added is the same as in the first embodiment. It is the same.

The thickness of the conductive film 31 is 0.05 to 0.2.
μm is preferred. The lower limit value of the film thickness of 0.05 μm is a limit value at which the function of the present invention cannot be achieved if the film thickness is further reduced. If the upper limit of the fork thickness of 0.2 μm is thicker than this, cracks are likely to occur on the surface of the conductive film 31 due to temperature changes. Moreover, it is economically unfavorable to increase the film thickness. Strictly speaking, it is desirable to form the conductive film 31 having a thickness corresponding to the particle size of the insulating auxiliary particles 30. (The thickness of the conductive film 31 is reduced as the particle size of the insulating auxiliary particles 30 is reduced).

As described above, according to this embodiment, the insulating auxiliary particles 3 are used.
The conductive auxiliary particles 33 having the surface of 0 covered with the conductive film 31 made of gold have a lower specific gravity than the metal and a particle size of 3 of silver powder.
When it is 3 to 10 times larger than 2, it diffuses well (uniformly) in the paste, and the silver powder 32 adheres to the periphery of the conductive auxiliary particles 33. The conductive auxiliary particles 33 act as an intermediary to stabilize the conductivity. or,
In the paste portion other than the surface of the conductive auxiliary particles 30, the silver powder 32 adheres to each other within a certain range, but the conductive auxiliary particles 33 serve as an appropriate intermediary to suppress this phenomenon to some extent.

As described above, the metal fine particles in the highly viscous liquid have the property of approaching the metal, and the silver powder 32 adheres to the surface of the conductive auxiliary particles 33 formed by coating gold as a conductive film. It is thought that this is also due to this property. The phenomenon in which the silver powder 32 approaches and contacts the surface of the conductive auxiliary particles 33 in this way has been confirmed by observing with a microscope by the inventor, and the effect of stabilizing the conductivity is also confirmed by conducting a trial run. is doing.

Also in this embodiment, as in the first embodiment, good conductive characteristics can be obtained by distributing the silver powder 32 around the conductive auxiliary particles 33 diffused in an appropriate state. did it. Further, since the conductive auxiliary particles 33 having a particle size larger than that of the silver powder 32 are appropriately diffused,
It has become possible to suppress the phenomenon that the silver powder 32 accumulates. As a result, the geometrical dimensions of the drive electrode (electrode width H,
When the thickness was the same as that of the conventional method, the variation in the resistance value could be reduced to 5% or less.

Although gold has been described as an example of the material of the conductive film 31 in this embodiment, in addition to the above-mentioned gold,
Similar effects were obtained when the conductive auxiliary particles were formed by plating or coating the insulating auxiliary particles 30 with nickel, silver or copper. Gold is most preferable in terms of long-term oxidation resistance and conductivity in comparison with other metals, but other properties such as nickel, silver, or copper are almost the same in terms of improving conductivity. Can be obtained.

When the first embodiment and the second embodiment are compared by experiments, it is confirmed that the second embodiment is slightly superior in the conductivity, that is, the variation in the resistance value.
It is considered that this is because the silver powders adhering to the surface of the conductive auxiliary particles are in a conductive state with each other, and as described above, a gold coating is formed on the surface of the auxiliary particles, which makes it easy to attract the silver powder. As a result of the observation, it is confirmed that the silver powder uniformly adheres to the surfaces of the insulating auxiliary particles even in the first embodiment. This phenomenon is considered to be due to the fact that particles with a small mass approach and adhere to particles with a large mass in a viscous fluid. Therefore, no metal coating is formed on the surface of the auxiliary particles. Also in the first embodiment, an effect comparable to that in the second embodiment can be obtained.

[0036]

According to the present invention, the spherical auxiliary particles play the role of a medium in the conductive paste forming the drive electrode on the substrate of the touch panel to realize uniform diffusion of the silver powder. Therefore, the addition ratio of silver powder can be reduced, and the original paste printing becomes possible. As a result, the quality of the drive electrodes with respect to conductivity is improved, and the reliability of the touch panel including the change over time and the yield are improved. Further, the width H of the drive electrode can be formed narrower than that in the conventional method, and the frame portion of the touch panel can be formed in a small area.
It is possible to reduce the external dimensions of the display surface. Furthermore,
The drive electrodes can be printed more easily than in the conventional method, and the number of steps and the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a partially enlarged view showing drive electrodes in a touch panel of the present invention.

FIG. 2 is a partially enlarged view showing a mixed state of insulating auxiliary particles and silver powder according to the first embodiment of the present invention.

FIG. 3 is a partially enlarged view showing a contact state between conductive auxiliary particles and silver powder according to the second embodiment of the present invention.

FIG. 4 is an exploded perspective view showing a touch panel in a conventional example.

[Explanation of symbols]

11 Upper substrate 12 Lower substrate 13 Laminating agent 14, 15, X-side drive electrode 16 Transparent electrode on upper substrate 17, 18 Upper substrate connection electrodes 19 Transparent electrode on the lower substrate 21, 22, 42 Y side drive electrode 23, 24 lower substrate connection electrodes 30 Insulating auxiliary particles 31 conductive film 32 silver powder 33 conductive auxiliary particles

Claims (7)

[Claims] 1. A touch panel comprising a transparent electrode formed on an upper substrate and a transparent electrode formed on a lower substrate facing each other with a gap therebetween, and a drive electrode connected to each transparent electrode, wherein the drive electrode is a resin. The solution is formed of a fired film of a conductive paste in which 30 to 45% by weight of silver powder and 15 to 25% by weight of spherical auxiliary particles are mixed, and the particle size of the silver powder is 0.
The touch panel is in the range of 1 to 5 μm, the average particle size of the spherical auxiliary particles is in the range of 1 to 20 μm, and satisfies the condition of 3 to 10 times the particle size of the silver powder. 2. The average particle size of the spherical auxiliary particles is 1 to 5 μm.
When the average particle size is less than 30%, the variation of the particle size is 30% or less, and when the average particle size is 5 to 20 μm, the variation of the particle size is 50% or less of the average particle size. The touch panel according to claim 1. 3. The touch panel according to claim 1, wherein the spherical auxiliary particles are insulating auxiliary particles such as plastic spheres, glass spheres, or ceramic spheres. 4. The touch panel according to claim 1, wherein the spherical auxiliary particles are conductive auxiliary particles obtained by coating the insulating auxiliary particles with a conductive film. 5. The conductive film has a thickness of 0.05 to 0.2 μm.
The touch panel according to claim 4, wherein the touch panel is m. 6. The touch panel according to claim 4, wherein the conductive film is gold. 7. The touch panel according to claim 1, wherein the drive electrode pattern is formed by using the conductive paste by printing.