JP4428609B2 - Touch panel - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention is a computer, various terminals, vending machines, ATMs, etc., which are arranged on a screen such as a liquid crystal display or a cathode ray tube, and a user displays an information display screen with a finger, a pen, etc. The present invention relates to a resistive film type analog touch panel in which data is input by directly pressing the input, and particularly relates to a touch panel with high electrode reliability.
[0002]
[Prior art]
A resistance 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. In the touch panel, a transparent substrate and a transparent substrate formed on a lower surface thereof, and a transparent substrate and a lower substrate formed on the upper surface of the transparent substrate are separated from each other with a predetermined space therebetween. Are arranged to face each other.
[0003]
In this touch panel, when the upper part 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 contacts 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. Hereinafter, an example of a touch panel in the prior art will be described with reference to the drawings.
[0004]
In the conventional touch panel, as shown in FIG. 4, the transparent electrode 18 formed on the flexible touch side (input side) upper substrate 11 and the transparent electrode 19 formed on the lower substrate 12 are insulative bonding agents. 13 are arranged opposite to each other with a gap provided therebetween. Also, a pair of parallel X-side drive electrodes 14 and 15 connected to the transparent electrode 18 of the upper substrate 11 and a pair of parallel Y-side drive electrodes 21 connected to the transparent electrode 19 of the lower substrate 12, And 22 are arranged to face each other in a square arrangement. Further, connection electrodes 16 and 17 connected to the X-side drive electrodes 14 and 15 of the upper substrate 11 are connected to connection electrodes 23 and 24 provided on the lower substrate 12 with a conductive adhesive, respectively. In general, the lower substrate is made of transparent glass and the upper substrate is made of a transparent film.
[0005]
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 and baking a silver paste on the upper substrate 11 and the lower substrate 12, respectively. The silver paste is prepared by mixing silver powder in a proportion of 60 to 85% by weight in a solution of a mature curable resin such as an epoxy resin or an acrylic resin. The particle size of the silver powder is generally 0.5 to 1.0 μm.
[0006]
[Problems to be solved by the invention]
However, not only silver but metal particles are naturally precipitated due to the specific gravity when immersed in a liquid. However, when the particles are about 5 μm or less, they are not completely precipitated and partially floated. This phenomenon becomes more remarkable as the viscosity of the liquid increases. Therefore, the metal fine particles are close to the diffusion state in the paste. However, the metal fine particles in the highly viscous liquid have a property that the metal particles attract each other, and it is considered that the silver powder tends to be agglomerated due to this property, and 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 a situation where silver powder accumulates in a lump and is scattered in the resin solution. However, it has been difficult to obtain stable conductivity.
[0007]
For this reason, it is necessary to increase the content of silver powder in the resin solution in order to ensure good conductivity of the electrode by the silver paste. As a result, it is damp rather than paste. As a result, the printing itself is difficult to perform, which is an obstacle to the uniformity of the thickness of the drive electrode formed, and the resistance value after firing varies by 20 to 30%. It was. In this way, the principle of making the conductor after curing by diffusing the silver powder into the resin solution is probabilistic, and it is an idea that some silver powder is connected and conduction is ensured as a whole. Therefore, the technique regarding the uniform diffusion of silver powder in the conductive paste is an important position.
[0008]
As a countermeasure to the above problem, a method for avoiding variation in resistance value by increasing the control width H of the electrode pattern or forming a thick printed film is disclosed. However, such a method has problems such as an increase in the outer dimensions of the touch panel and an increase in man-hours.
[0009]
(Object of invention)
An object of the present invention is to solve the above-described problems, avoid variations in resistance values of drive electrodes, and provide a highly reliable touch panel.
[0010]
[Means for Solving the Problems]
In order to achieve the above-described object, a touch panel according to the invention of claim 1 is included in the present invention.
In the touch panel having a drive electrode connected to each transparent electrode, the transparent electrode formed on the upper substrate and the transparent electrode formed on the lower substrate are arranged to face each other with a gap therebetween,
The drive electrode has a mean particle size of 1 to 20 μm in a conductive paste obtained by adding 30 to 45% by weight of silver powder having a particle size of 0.1 to 5 μm to a highly viscous resin solution in which metal particles attract each other. And 15 to 25% by weight of spherical auxiliary particles having a particle size 3 to 10 times larger than the particle size of the silver powder, so that the silver powder is uniformly diffused in the paste. A touch panel comprising a fired film formed using a conductive paste mixed with the spherical auxiliary grains .
[0011]
In the touch panel according to the second aspect of the present invention, in the touch panel according to the first aspect, when the average particle size of the spherical auxiliary particles is less than 1 to 5 μm, the variation in the particle size is the average particle size. When the average particle size is 5 to 20 μm, the variation in particle size is 50% or less of the average particle size.
[0012]
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 grains are insulating auxiliary grains such as plastic spheres, glass spheres, or ceramic spheres. It is characterized by comprising.
[0013]
The touch panel according to claim 4 of the present invention is the touch panel according to claim 1 or 2, wherein the spherical auxiliary grains are conductive auxiliary grains obtained by coating the insulating auxiliary grains with a conductive film. It is characterized by comprising.
[0014]
The touch panel according to a fifth aspect of the present invention is the touch panel according to the fourth aspect, wherein the conductive film has a thickness of 0.05 to 0.2 μm. It is a touch panel.
[0015]
The touch panel according to a sixth aspect of the present invention is the touch panel according to the fourth or fifth aspect, wherein the conductive film is gold.
[0017]
(Function)
In the conductive paste in the touch panel of the present invention, the insulating auxiliary grains such as ceramic spheres, glass spheres, or plastic spheres having a size larger than the silver powder are diffused together with the silver powder in the resin solution, and the surroundings of the insulating auxiliary grains Silver powder is distributed on the surface. This suppresses the occurrence of a situation where silver powder is accumulated in the conductive paste and is scattered in the resin solution, and the silver powder is uniformly diffused to obtain a drive electrode having stable conductivity. Can do.
[0018]
Furthermore, by diffusing the conductive auxiliary grains in which the insulating auxiliary grains are coated with the conductive film together with the silver powder in the resin solution, more stable conductivity can be obtained, and the conductivity of the drive electrode formed on the conductive film can be obtained. Further improve quality related to sex. Hereafter, it explains in full detail by embodiment of this invention.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a cross-sectional view showing a part of the Y-side drive electrode 42 of the touch panel in the present embodiment. FIG. 2 is a partially enlarged view showing a diffusion state of the insulating auxiliary grains 30 and the silver powder 32 in the conductive paste in the present embodiment. In addition, since the whole structure of the touchscreen in this embodiment is the same as that of a prior art example, description is abbreviate | omitted. Hereinafter, the present embodiment will be described with reference to the drawings.
[0020]
As shown in FIGS. 1 and 2, the Y-side drive electrode 42 of the touch panel in this embodiment is a conductive material obtained by mixing insulating auxiliary grains 30 as spherical auxiliary grains together with silver powder 32 in an epoxy resin solution of a mature curable resin. The paste is printed on the lower substrate 12 and baked to form a low resistance electrode.
[0021]
The ratio of the silver powder 32 added to the conductive paste is set to 30 to 45% by weight before drying about half of the conventional method. In addition, 15 to 25% by weight of the insulating auxiliary grains 30 having a certain particle size adjusted together with the silver powder 32 is added before drying. The insulating auxiliary grains may be plastic spheres, ceramic spheres, or glass spheres. For example, the ceramic spheres include alumina (Al ₂ O ₃ ), and the glass spheres include silica glass (SiO).
[0022]
The ceramic sphere (specific gravity around 1.9) and the silica glass (specific gravity around 2.0) and the plastic sphere (specific gravity around 1.0) are not markedly different despite the specific gravity being different. The same effect was obtained. The reason is considered that when the ceramic sphere has a porous structure, the effective specific gravity is not much different from that of the plastic sphere.
[0023]
In addition, the size of the insulating auxiliary grain 30 to be added may be 1 to 20 μm in size, but in the case of the present invention, the size of the grain size of the silver powder 32 to be added simultaneously may be selected to be 3 to 10 times. It is important to get an effect.
[0024]
Further, the variation in the outer diameter of the insulating auxiliary grains 30 to be added is such that when the average particle diameter of the insulating auxiliary grains 30 is less than 1 to 5 μm, the variation in the particle diameter is 30% or less of the average particle diameter. When the diameter is 5 to 20 μm, it is desirable that the variation in the particle size is suppressed to 50% or less of the average particle size.
[0025]
In this 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.
[0026]
As described above, according to the present embodiment, good conductive characteristics can be obtained by distributing the silver powder 32 around the auxiliary insulating grains 30 such as ceramic spheres, plastic spheres, or glass spheres diffused in an appropriate state. It was. Further, since the insulating auxiliary grains 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 accumulates. As a result, the variation in resistance value was reduced to 5% or less when the shape dimensions (electrode width H, thickness) of the drive electrode were the same as those in the conventional method.
[0027]
(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 grains 33 and the silver powder 32 as spherical auxiliary grains in the conductive paste in the present embodiment. Note that a description of the same parts as those in the first embodiment will be omitted. Hereinafter, the present embodiment will be described with reference to the drawings.
[0028]
As shown in FIG. 3, the conductive paste in this embodiment is different from the first embodiment in that conductive auxiliary grains 33 as spherical auxiliary grains are mixed with silver powder 32 in an epoxy resin solution of a mature curable resin. Others are the same.
[0029]
In this embodiment, the ratio 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 conductive auxiliary grains 33 obtained by coating the surface of the insulating auxiliary grains 30 with the silver powder 32 having a certain particle size with a gold conductive film 31 by a method such as electroless plating are 15- Add 25%.
The insulating auxiliary grains 30 can be plastic spheres, ceramic spheres, glass spheres, etc., as in the first embodiment. The particle diameter of the insulating auxiliary grains 30 to be added is the same as that of the first embodiment. It is the same.
[0030]
The film thickness of the conductive film 31 is preferably 0.05 to 0.2 μm. The lower limit value of the film thickness of 0.05 μm is a limit value at which the function of the present invention is not achieved if the thickness is further reduced. If the upper limit value of the fork film thickness is 0.2 μm or more, cracks are likely to occur on the surface of the conductive film 31 due to temperature changes. In addition, it is not economically preferable 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 grains 30. (The thickness of the conductive film 31 is reduced as the particle size of the insulating auxiliary grains 30 is reduced).
[0031]
As described above, according to the present embodiment, the conductive auxiliary grains 33 in which the surface of the insulating auxiliary grains 30 is coated with the conductive film 31 made of gold have a specific gravity lower than that of metal and a particle diameter of 32 By being larger than 10 times, it diffuses well (uniformly) in the paste, and the silver powder 32 adheres around the conductive auxiliary grains 33. The conductive auxiliary grains 33 serve as an intermediary to stabilize the conductivity. In addition, the paste portion other than the surface of the conductive auxiliary grain 30 is generated within a range where the silver powder 32 adheres to each other, but the conductive auxiliary grain 33 acts as an appropriate mediator to suppress this phenomenon to some extent.
[0032]
Thus, 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 grains 33 formed by coating gold as a conductive film. This is considered to be due to this property. The phenomenon in which the silver powder 32 approaches and comes into contact with the surface of the conductive auxiliary grain 33 in this way has been observed and confirmed by the inventor with a microscope, and further confirmed that the conductivity is stabilized by conducting a trial production. is doing.
[0033]
Also in the present embodiment, as in the first embodiment, the silver powder 32 is distributed around the conductive auxiliary grains 33 diffused in an appropriate state, whereby good conductive characteristics can be obtained. In addition, since the conductive auxiliary grains 33 having a particle diameter larger than that of the silver powder 32 are appropriately diffused, it is possible to suppress the phenomenon that the silver powder 32 accumulates. As a result, the variation in resistance value was reduced to 5% or less when the shape dimensions (electrode width H, thickness) of the drive electrode were the same as those in the conventional method.
[0034]
In the present embodiment, gold is described as an example of the material of the conductive film 31. However, in addition to the above-described gold, nickel, silver, or copper is plated or coated on the insulating auxiliary grain 30 to form the conductive auxiliary grain. Even when the film was formed, substantially the same effect was obtained. Gold having superior properties over other metals in terms of long-term oxidation resistance and conductivity is most preferable, but in terms of improving conductivity, other nickel, silver, or copper is almost the same. Effects can be obtained.
[0035]
When the first embodiment and the second embodiment are compared by experiment, it is confirmed that the second embodiment is slightly superior in terms of conductivity, that is, variation in resistance value. This is thought to be because the silver powders adhered to the surface of the conductive auxiliary grains are in a conductive state with each other, and as described above, the gold continuous film is formed on the surface of the auxiliary grains, and it is easy to attract the silver powder. As a result of the observation, it is confirmed that the silver powder is uniformly adhered to the surface of the insulating auxiliary grains also in the first embodiment. This phenomenon is considered to be due to the property that particles with a small mass approach and adhere to particles with a large mass in a viscous fluid. Therefore, no metal film is formed on the auxiliary grain surface. Also in the first embodiment, an effect comparable to that of the second embodiment can be obtained.
[0036]
【The invention's effect】
According to the present invention, in the conductive paste that forms the drive electrode on the substrate of the touch panel, the spherical auxiliary particles serve as a medium, and uniform diffusion of the silver powder is realized. Therefore, the addition ratio of silver powder can be reduced and original paste printing becomes possible.
As a result, the quality related to the conductivity of the drive electrode is improved, and the reliability including the change with time of the touch panel and the yield are improved.
In addition, the width H of the drive electrode can be made narrower than that of the conventional method, the frame part of the touch panel can be formed with a small area, and the external dimensions with respect to the display surface can be reduced.
Furthermore, printing of the drive electrode can be performed more easily than the conventional method, and man-hour reduction and cost reduction can be realized.
[Brief description of the 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 grains and silver powder in the first embodiment of the present invention.
FIG. 3 is a partially enlarged view showing a contact state between conductive auxiliary grains and silver powder in a second embodiment of the present invention.
FIG. 4 is an exploded perspective view showing a conventional touch panel.
[Explanation of symbols]
11 Upper substrate 12 Lower substrate 13 Bonding agent 14, 15 X side drive electrode
18 Transparent electrode on upper substrate
16, 17 Upper substrate connection electrode 19 Lower substrate transparent electrodes 21, 22, 42 Y-side drive electrodes 23, 24 Lower substrate connection electrode 30 Insulating auxiliary grains 31 Conductive film 32 Silver powder 33 Conductive auxiliary grains

Claims (6)

In the touch panel having a drive electrode connected to each transparent electrode, the transparent electrode formed on the upper substrate and the transparent electrode formed on the lower substrate are arranged to face each other with a gap therebetween,
The drive electrode has a mean particle size of 1 to 20 μm in a conductive paste obtained by adding 30 to 45% by weight of silver powder having a particle size of 0.1 to 5 μm to a highly viscous resin solution in which metal particles attract each other. And 15 to 25% by weight of spherical auxiliary particles having a particle size 3 to 10 times larger than the particle size of the silver powder, so that the silver powder is uniformly diffused in the paste. A touch panel comprising a fired film formed using a conductive paste mixed with the spherical auxiliary grains .   When the average particle size of the spherical auxiliary particles is less than 1 to 5 μm, the particle size variation is 30% or less of the average particle size, and when the average particle size is 5 to 20 μm, the particle size variation is the average particle size. The touch panel according to claim 1, wherein the touch panel has a diameter of 50% or less.   The touch panel according to claim 1, wherein the spherical auxiliary grains are made of insulating auxiliary grains such as plastic spheres, glass spheres, or ceramic spheres. The touch panel according to claim 3 , wherein the spherical auxiliary grains are made of conductive auxiliary grains obtained by coating the insulating auxiliary grains with a conductive film.   The touch panel according to claim 4, wherein the conductive film has a thickness of 0.05 to 0.2 μm.   6. The touch panel according to claim 4, wherein the conductive film is gold.

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