JP2024067642A - Touch Panel - Google Patents

Abstract

To provide a transparent touch panel of an analog resistive film system for detecting a touch position without using a transparent conductive film comprising ITO (Indium Tin Oxide).SOLUTION: A touch panel 1 includes: a pair of transparent substrates 2 and 3 arranged to face each other with a small gap therebetween; first and second mesh resistors formed in a mesh shape made of metal-made thin wires on the facing surfaces of the pair of transparent substrates so as not to be visible to the naked eye; a spacer member provided on one of the pair of transparent substrates to hold the first and second mesh resistors in a non-contact state; and detection means (detection circuit 7) for detecting the contact position of the first and second mesh resistors that come into contact by touching the transparent substrate 2 of the pair of transparent substrates arranged on a front side, as a change in resistance value by applying voltages to both ends of the first and second mesh resistors, respectively.SELECTED DRAWING: Figure 1

Description

The present invention relates to a transparent analog resistive touch panel that is used in combination with a display panel such as a liquid crystal panel or an organic EL panel.

Conventionally, resistive touch panels have often used a transparent conductive film made of ITO (Indium Tin Oxide). The ITO that forms the transparent conductive film is made from indium (In), which is a rare metal and has become difficult to obtain in recent years.

Furthermore, when forming an ITO film by vacuum sputtering, high temperatures must be applied, which leads to the emission of _CO2 , and is therefore undesirable from the viewpoint of global warming, which has become a hot topic recently.

Furthermore, the ITO film that forms the transparent conductive film must have a high resistance and high transparency, so it generally needs to be formed with a very thin film thickness of 100 to 150 Å. The ITO film is an amorphous film made by doping indium (In) and tin (Sn) with oxygen and is not crystallized, so generally the thinner the film, the more unstable the structure of the film becomes. Therefore, when an ITO film is used as a transparent conductive film for a touch panel, it is difficult to control the film quality to be uniform within the surface, and there is a large variation in the resistance value within the surface, which limits the accuracy of detecting the touch position. In addition, the ITO film that forms the transparent conductive film has a technical problem in that the resistance value is easily changed due to the influence of temperature, and the operating characteristics are not stable.

Incidentally, touch panel technologies have already been proposed, for example those disclosed in Patent Documents 1 and 2.

Patent Document 1 discloses a resistive film type touch panel having a rectangular first region capable of receiving a touch operation that brings an upper electrode having a transparent conductive film into contact with a lower electrode, and a second region arranged to surround the first region, and capable of detecting the position on the first region where the touch operation was performed from the voltage value of the conductivity caused by the contact. The transparent conductive film is arranged to overlap the first region and the second region, and etching portions are formed in the regions overlapping with the first region near the opposing sides of the first region.

Patent document 2 discloses an upper electrode substrate having an upper conductive film, a lower electrode substrate having a lower conductive film, a first power supply terminal, a second power supply terminal, and a third power supply terminal provided at each of the four corners of the lower electrode substrate, a fourth power supply terminal disposed diagonally from the first power supply terminal, and resistors disposed between the second power supply terminal, the third power supply terminal, and the fourth power supply terminal and a power supply potential, and when measuring in a first direction, the first power supply terminal and the third power supply terminal are grounded. , a power supply potential is supplied to the second power supply terminal and the fourth power supply terminal via a resistor, and a divided voltage value at the second power supply terminal and the fourth power supply terminal is detected. When measuring in a second direction intersecting the first direction, the first power supply terminal and the second power supply terminal are grounded, and a power supply potential is supplied to the third power supply terminal and the fourth power supply terminal via a resistor, and a divided voltage value at the third power supply terminal and the fourth power supply terminal is detected.

JP 2021-149554 A JP 2018-152105 A

The objective of the present invention is to provide a transparent touch panel using an analog resistive film method that can detect the touch position without using a transparent conductive film made of ITO (Indium Tin Oxide).

The present invention described in claim 1 comprises a pair of transparent substrates arranged to face each other with a small gap therebetween;
a first mesh resistor and a second mesh resistor each formed in a mesh shape made of thin metal wires on the opposing surfaces of the pair of transparent substrates so as not to be visually recognized;
a spacer member provided on one of the pair of transparent substrates and configured to hold the first and second mesh resistors in a non-contact state;
a detection means for detecting a contact position of the first and second mesh resistors that is contacted by touching the transparent substrate disposed on the front side of the pair of transparent substrates as a change in resistance value by applying a voltage to both ends of the first and second mesh resistors, respectively;
It is a touch panel equipped with.
The invention described in claim 2 is the touch panel described in claim 1, wherein the transparent substrate located on the front side of the pair of transparent substrates has a decorative portion on its outer periphery.

The invention described in claim 3 is the touch panel described in claim 1, in which the first and second mesh resistors are each formed in a mesh shape that intersects at a predetermined pitch, and are arranged in a staggered manner so as not to overlap each other.

The invention described in claim 4 is the touch panel described in claim 3, in which the first and second mesh resistors are arranged parallel to each other at a pitch of 100 μm to 5 mm.

The invention described in claim 5 is the touch panel described in claim 1, in which the first and second mesh resistors are formed in the form of thin wires of a metal or alloy of either titanium (Ti) or chromium (Cr).

The invention described in claim 6 is the touch panel described in claim 5, in which the first and second mesh resistors have a film thickness of 500 to 2000 Å and a line width of 1 to 100 μm.

The invention described in claim 7 is the touch panel described in claim 6, in which the first and second mesh resistors have a resistance value per unit area of 400 to 2000 Ω/□.

The invention described in claim 8 is the touch panel described in claim 1, in which the pair of transparent substrates are made of tempered glass, and the transparent substrate located on the front side of the pair of transparent substrates also serves as a cover glass.

The invention described in claim 9 is the touch panel described in claim 8, in which the transparent substrate located on the front side of the pair of transparent substrates is made of a glass plate having a thickness of 0.1 to 0.5 mm, and the transparent substrate located on the back side is made of a glass plate having a thickness of 0.5 to 3.0 mm.

The invention described in claim 10 is characterized in that one of the pair of transparent substrates has opposite opposite end edges formed with a pair of first current-carrying electrodes for passing current through the first mesh resistor, and the other transparent substrate has opposite opposite end edges formed with a pair of second current-carrying electrodes for passing current through the second mesh resistor,
2. The touch panel according to claim 1, wherein the first and second current-carrying electrodes are extended to positions of current-carrying terminals provided on parts of outer peripheries of the pair of transparent substrates.

The invention described in claim 11 is the touch panel described in claim 10, in which the current-carrying terminal is provided on the transparent substrate located on the front side of the pair of transparent substrates, and the lead-out portion of one current-carrying electrode provided on the transparent substrate located on the back side of the pair of transparent substrates is connected to the current-carrying terminal provided on the transparent substrate located on the front side via a conductive member when the pair of transparent substrates are arranged to face each other with a small gap between them.

The invention described in claim 12 is the touch panel described in claim 1, in which the pair of transparent substrates are formed to have the same shape.

The invention described in claim 13 is the touch panel described in claim 1, in which the transparent substrate located on the back side of the pair of transparent substrates has an opening for attaching a flexible printed circuit board for passing electricity through the first and second mesh resistors.

The present invention provides a transparent touch panel using an analog resistive film method that can detect a touch position without using a transparent conductive film made of ITO (Indium Tin Oxide).

1A and 1B are a front view and a rear view showing a transparent analog resistive film touch panel according to a first embodiment of the present invention. FIG. 2 is an enlarged view showing area II in FIG. FIG. 3 is an enlarged view showing area III in FIG. FIG. 4 is an enlarged schematic view showing the first electrode. FIG. 5 is an enlarged schematic view showing the second electrode. FIG. 6 is an enlarged cross-sectional view showing the state in which the first and second electrodes are formed. FIG. 7 is an enlarged schematic view showing the first electrode. FIG. 8 is an enlarged schematic view showing the second electrode. FIG. 9 is a configuration diagram showing a connection state of a flexible printed circuit board. FIG. 10 is a plan view showing the configuration of a flexible printed circuit board. FIG. 11 is a configuration diagram showing a connection state of a flexible printed circuit board. FIG. 12 is a table showing the results of Experimental Example 1. FIG. 13 is a graph showing the results of Experimental Example 1. FIG. 14 is a graph showing the results of Experimental Example 1. FIG. 15 is a table showing the results of Experimental Example 2. FIG. 16 is a table showing the results of Experimental Example 2.

Below, an embodiment of the present invention will be described with reference to the drawings.

[Embodiment 1]
1A and 1B are a front view and a rear view, respectively, showing a transparent analog resistive film touch panel according to a first embodiment of the present invention.

The touch panel according to the first embodiment is used in combination with, for example, display devices such as liquid crystal panels or organic EL (Electro Luminescence) panels in machine tools, vending machines, etc., fixed-displays such as the display units of personal computers, televisions, and home appliances, and further with portable display devices such as smartphones, mobile phones, notebook personal computers, tablets, and PDAs (Personal Digital Assistants).

As shown in Figs. 1(a) and 1(b), the touch panel 1 according to the first embodiment is roughly divided into a pair of transparent substrates 2, 3 arranged to face each other with a small gap therebetween, first and second mesh resistors 4, 5 (see Fig. 2) formed in a fine mesh shape on the facing surfaces of the pair of transparent substrates 2, 3, respectively, a spacer member 6 (see Fig. 3) interposed between the pair of transparent substrates 2, 3 and holding the first and second mesh resistors 4, 5 in a non-contact state, and a detection circuit 7 as an example of a detection means for detecting the contact positions of the first and second mesh resistors 4, 5 that come into contact when the transparent substrate 2 arranged on the front side of the pair of transparent substrates 2, 3 is touched as a change in resistance value by passing current through both ends of the first and second mesh resistors 4, 5, respectively.

The pair of transparent substrates 2, 3 are, for example, both made of transparent glass substrates. Here, the transparent substrate 2 located on the front side of the pair of transparent substrates 2, 3 is referred to as the first transparent substrate, and the transparent substrate 3 located on the back side is referred to as the second transparent substrate. Examples of glass materials constituting the first and second transparent substrates 2, 3 include glass materials such as soda lime glass, aluminosilicate glass, and borosilicate glass. However, the glass materials constituting the first and second transparent substrates 2, 3 are not limited to these, and other glass materials may of course be used. In addition, the first and second transparent substrates 2, 3 are not necessarily limited to those made of glass materials, and those made of transparent synthetic resins such as polyethylene terephthalate resin, polycarbonate resin, polymethyl methacrylate resin, urethane resin, thiourethane resin, and polyimide resin may also be used.

When using glass substrates as the first and second transparent substrates 2 and 3, it is preferable to use glass substrates made of chemically or physically strengthened glass.

The first and second transparent substrates 2, 3 are formed such that the first transparent substrate 2 is thinner than the second transparent substrate 3. The first transparent substrate 2 is, for example, a glass substrate having a thickness of 0.33 mm, and the second transparent substrate 3 is, for example, a glass substrate having a thickness of 1.1 mm.

However, the thicknesses of the first and second transparent substrates 2, 3 are not limited to the above values, and the first transparent substrate 2 may have a thickness of, for example, about 0.1 to 0.5 mm, and the second transparent substrate 3 may have a thickness of about 0.5 to 3.0 mm. If the first transparent substrate 2 is less than 0.1 mm thick, it may be insufficient in strength, and if it exceeds 0.5 mm thick, it may be possible for the detection accuracy to decrease when touched with a finger or the like. Furthermore, if the second transparent substrate 3 is less than 0.5 mm thick, it may be insufficient in strength, and if it exceeds 3.0 mm thick, it is undesirable because the weight of the touch panel 1 increases unnecessarily.

As shown in FIG. 1, the first and second transparent substrates 2 and 3 are formed in the same shape. In a conventional touch panel, the second transparent substrate 3 is set larger than the first transparent substrate 2 because a flexible printed circuit board for passing electricity through the transparent conductive film provided on the first and second transparent substrates 2 and 3 is attached to the second transparent substrate 3, etc. In contrast, when the first and second transparent substrates 2 and 3 are formed in the same shape, there is no area in which one of the first and second transparent substrates 2 and 3 exists, so that even if the thickness of the first and second transparent substrates 2 and 3 is relatively thin, the mechanical strength can be improved. The first and second transparent substrates 2 and 3 according to the first embodiment are formed in a horizontally elongated rectangular shape in plan view, for example, with the horizontal side (X direction in the figure) longer than the vertical side (Y direction in the figure). However, the shape of the first and second transparent substrates 2 and 3 is arbitrary and is not limited to a horizontally elongated rectangular shape, and may of course be a square shape, a vertically elongated rectangular shape, or a trapezoidal shape. The left and right corners 8, 9 located at the upper ends of the first and second transparent substrates 2, 3 are formed in an R shape (curved shape).

A flexible printed circuit (FPC) 10 for passing electricity through the first and second mesh resistors 4 and 5 is attached to the center of the lower end of the first transparent substrate 2 on the rear surface of the first transparent substrate 2. On the other hand, as shown in FIG. 1B, the second transparent substrate 3 is provided with a notch 11 as an example of an opening cut out from the center of the lower end of the second transparent substrate 3 in order to attach the flexible printed circuit 10 to the rear surface of the first transparent substrate 2. Note that the opening for attaching the flexible printed circuit 10 to the touch panel 1 is not limited to the notch 11 provided on the rear surface of the first transparent substrate 2, and a hole drilling process may be performed to provide an insertion hole as an example of an opening in the second transparent substrate 3, so that a connection electrode for connecting to the flexible printed circuit 10 is drawn to the rear surface of the second transparent substrate 3, and the flexible printed circuit 10 is attached to the rear surface of the second transparent substrate 3.

As shown in FIG. 1(a), the back surface of the first transparent substrate 2 is provided with a decorative portion 12 that forms a border (adds decoration) around the outer periphery. The decorative portion 12 of the first transparent substrate 2 is formed in a strip shape having a required width (e.g., about 10 mm) so as to cover the entire outer periphery of the first transparent substrate 2. In the present embodiment 1, the material of the decorative portion 12 is PhotoBlack (registered trademark), which is a black pigment with excellent light-shielding properties. However, the material of the decorative portion 12 is not limited to PhotoBlack (registered trademark), and it goes without saying that the color may be set to a color other than black.

The first transparent substrate 2 is provided with a decorative portion 12, which forms a display portion 13 consisting of a planar rectangular opening of a predetermined size formed in the first transparent substrate 2. The display portion 13 is a portion that displays an image of a display means such as a liquid crystal display panel or an EL display panel arranged on the back side of the touch panel 1. The display portion 13 is also an effective area where the touch panel 1 can detect a touch position. As described below, the decorative portion 12 of the first transparent substrate 2 is formed on the outer periphery of the first and second transparent substrates 2 and 3, and also serves the function of making the current-carrying electrodes for passing current through the first and second mesh resistors 4 and 5 and the connection portion of the flexible printed circuit board 10 invisible (hiding) from the outside.

Compared to when the decorative portion 12 is not provided, the first transparent substrate 2 does not require an outer frame component such as a bezel that covers the outer periphery of the first and second transparent substrates 2 and 3, and the decorativeness of the touch panel 1 is improved while the touch panel 1 can be placed directly in front of a display device such as a liquid crystal panel (not shown) for easier installation.

As shown in FIG. 4, the first and second transparent substrates 2, 3 are arranged to face each other with a small gap between them. A gap setting member 14 that sets the gap between the first and second transparent substrates 2, 3 is arranged around the entire periphery of the first and second transparent substrates 2, 3. The gap setting member 14 covers the entire periphery of the first and second transparent substrates 2, 3, and thereby also serves the function of increasing the airtightness of the space 15 formed between the first and second transparent substrates 2, 3.

The gap setting member 14 is made of a material such as synthetic resin. The gap setting member 14 is attached to the first and second transparent substrates 2, 3 via a pressure sensitive adhesive or glue (not shown), thereby holding and fixing the first and second transparent substrates 2, 3 so that they face each other with a predetermined minute gap in between. The gap between the first and second transparent substrates 2, 3, i.e., the thickness of the gap setting member 14, is set to, for example, about 2 to 30 μm.

As shown in FIG. 5, the opposing surfaces of the first and second transparent substrates 2 and 3 are provided with first and second mesh resistors 4 and 5, which are formed in a mesh shape made of thin metal wires so as not to be visible to the naked eye. The first and second mesh resistors 4 and 5 function as transparent resistive films that are not visible to the naked eye. Note that FIG. 5 is an enlarged schematic diagram showing the first and second mesh resistors 4 and 5 formed on the opposing surfaces of the first and second transparent substrates 2 and 3 as viewed from the front side.

The touch panel 1 according to the first embodiment is a transparent touch panel that employs an analog resistive film method. Metal, which is a conductor, is an opaque material that does not transmit light, unlike a transparent conductive film made of ITO (Indium Tin Oxide).

While intensively researching materials to replace the conventional transparent conductive film made of ITO (Indium Tin Oxide), the inventors discovered that even if the material is a metal, it is possible to make it function as a transparent resistive film that is invisible to the naked eye by forming extremely fine, thin linear electrodes into a mesh shape.

As is well known, the resistance R of a conductor such as a metal having a constant cross-sectional area is given by the following formula:
R = ρ(L/A)
= ρ {L/(WT)}
Here, L is the length of the conductor (m), A is the cross-sectional area of the conductor ( ^m2 ), and ρ is the electrical resistivity (Ω·m) determined by the material of the conductor. For example, in the case of a conductor with a rectangular cross section, the cross-sectional area A is calculated by the product W·T of the line width W and layer thickness T of the conductor.

First, the first and second mesh resistors 4, 5 must have a line width W that is not visible to the naked eye. To achieve this, it is desirable for the line width W of the resistance wires that make up the first and second mesh resistors 4, 5 to be thin, but considering the mechanical strength of the touch panel 1 when repeatedly subjected to pressure and the sheet resistance value as a planar resistive film, it is desirable for the line width W of the resistance wires that make up the first and second mesh resistors 4, 5 to be 1 to 100 μm. If the line width W of the resistance wire is less than 1 μm, this is undesirable from the standpoint of mechanical strength, and if it exceeds 100 μm, it becomes easily visible and is undesirable from the standpoint of transparency.

The layer thickness T of the resistance wire constituting the first and second mesh resistors 4, 5 determines the resistance value of the first and second mesh resistors 4, 5, and is set to 500 to 2000 Å in this embodiment 1. If the layer thickness T of the resistance wire is less than 500 Å, it is undesirable in terms of the strength of the portion drawn out to the outer periphery of the first and second transparent substrates 2, 3 and the mechanical strength against repeated loads by the touch panel 1. If the layer thickness T of the resistance wire exceeds 2000 Å, the resistance value may be too low from the viewpoint of the first and second mesh resistors 4, 5 acting as a transparent resistive film, which is undesirable. In this embodiment 1, the layer thickness T of the resistance wire of the first and second mesh resistors 4, 5 is set to 800 Å.

The material of the conductors constituting the first and second mesh resistors 4, 5, together with the line width W and layer thickness T of the resistance wire, determines the overall resistance value of the first and second mesh resistors 4, 5, which act as a transparent resistive film, and is therefore a very important factor.

When copper (Cu) or aluminum (Al), which are commonly used in capacitive touch panels, are used as the conductive material constituting the first and second mesh resistors 4 and 5, the electrical resistivity of copper (Cu) is 1.68× ^10-8 (Ω·m), and the electrical resistivity of aluminum is 2.65× ^10-8 (Ω·m).

Therefore, if copper (Cu) or aluminum (Al) is used as the material of the conductor that constitutes the first and second mesh resistors 4, 5, in order to achieve the desired resistance value of the entire first and second mesh resistors 4, 5, the line width W and layer thickness T of the resistance wires of the first and second mesh resistors 4, 5 must be set to significantly small values. Although this is not a problem from the viewpoint of transparency, it is inappropriate because it significantly weakens the mechanical strength.

The conductive material constituting the first and second mesh resistors 4, 5 must satisfy all of the requirements in terms of transparency for visibility, mechanical strength for use as a resistive film for the touch panel 1, and line width W and layer thickness T for functioning as a transparent resistive film with the desired resistance value.

As described above, the inventors have been conducting intensive research into alternative materials to the conventional transparent conductive film made of ITO (Indium Tin Oxide), and have found that metals such as titanium (Ti) or chromium (Cr) are suitable as metal materials or alloys or compounds thereof.

The electrical resistivity of titanium (Ti) is 4.20×10 ⁻⁷ (Ω·m), and the electrical resistivity of chromium (Cr) is 1.29×10 ⁻⁷ (Ω·m), which is slightly lower than that of titanium (Ti) and is approximately one order of magnitude higher than the above-mentioned copper (Cu) and aluminum (Al), etc. An ITO (Indium Tin Oxide) film has a higher electrical resistivity than titanium (Ti) and chromium (Cr).

A conventional transparent conductive film made of ITO (Indium Tin Oxide) is formed uniformly (so-called "solid") on the surface of a transparent substrate, and has a resistance value per unit area (10 mm ² ) of 400 to 800 Ω/□.

In contrast, when the first and second mesh resistors 4, 5 made of titanium (Ti), 5μ wide and 800 Å thick, are formed at a pitch of 0.5 mm, the resistance per unit area ( ¹⁰ mm2) is about 785.2Ω/□.On the other hand, when the first and second mesh resistors 4, 5 made of chromium (Cr), 3μ wide and 800 Å thick, are formed at a pitch of 0.5 mm, the resistance per unit area ( ¹⁰ mm2) is also about 785.2Ω/□.

As shown in Fig. 6, the first and second mesh resistors 4, 5 are not transparent electrodes such as ITO (Indium Tin Oxide) films, but are formed on the opposing surfaces of the first and second transparent substrates 2, 3 by processes such as forming and etching a conductive layer, and are made of opaque metal thin wires with a line width W and a film thickness T that are not visible to the naked eye. Therefore, unlike the ITO film, there is no need to form the film by a vacuum sputtering method or the like performed in a high-temperature environment, and it is desirable from the viewpoint of global warming and the like because it does not involve the emission of _CO2 . In addition, chromium (Cr) can also be used as the first and second mesh resistors 4, 5, but titanium (Ti) is preferable from the viewpoint of safety to the human body and the like.

In the first embodiment, the first and second mesh resistors 4 and 5 are made of a thin film of the metal titanium (Ti). Titanium (Ti), an example of a conductive material, is an opaque metal material that does not transmit light. As described above, titanium (Ti) is desirable because it has a relatively high electrical resistivity and is easier to form a straight, extremely thin wire having a required film thickness with high precision in a uniform and excellent linearity state compared to an ITO film. Furthermore, titanium (Ti) has high adhesion to the first and second transparent substrates 2 and 3 made of glass substrates, etc., and has sufficient mechanical strength to be resistant to deformation under repeated pressure loads.

In the first embodiment, as described above, the first and second mesh resistors 4 and 5 are made of very thin strip-shaped (thin wire) electrodes made of titanium (Ti) with a film thickness T of 800 Å and a line width W of 5 μm, which are formed in a mesh shape.

A first mesh resistor 4 is formed on the back surface of the first transparent substrate 2. A second mesh resistor 5 is formed on the front surface of the second transparent substrate 3, which is the surface facing the first transparent substrate 2.

As shown in the enlarged schematic diagram of FIG. 7, the first mesh resistor 4 is formed by forming very thin strip-shaped (thin-line) resistance wires 41 in a mesh (lattice) shape on the back surface of the first transparent substrate 2. The thin-line resistance wires 41 are arranged to intersect at a 90-degree angle with a predetermined pitch P (e.g., about 500 μm) as shown in FIG. 2. One of the intersecting thin-line resistance wires 41 of the first mesh resistor 4 is arranged to be inclined at an angle of 22.5 degrees with respect to the horizontal X direction. Therefore, the other of the intersecting thin-line resistance wires 41 of the first mesh resistor 4 is arranged to be inclined at an angle of 112.5 degrees (22.5 degrees + 90 degrees) with respect to the horizontal X direction.

On the other hand, the second mesh resistor 5 is formed by forming very thin strip-shaped (thin wire-shaped) resistance wires 51 in a mesh (lattice) shape on the surface of the second transparent substrate 3, as shown in the enlarged schematic diagram in FIG. 8. The thin wire-shaped resistance wires 51 are arranged to intersect at a 90-degree angle at a predetermined pitch P (for example, about 500 μm) as in the first mesh resistor 4, as shown in FIG. 2. One of the intersecting thin wire-shaped resistance wires 51 of the second mesh resistor 5 is arranged to be inclined at an angle of 22.5 degrees with respect to the horizontal X direction. The other of the intersecting thin wire-shaped resistance wires 51 of the second mesh resistor 5 is arranged to be inclined at an angle of 112.5 degrees (22.5 degrees + 90 degrees) with respect to the horizontal X direction. Note that the meshes forming the first and second mesh resistors 4 and 5 do not necessarily have to have an intersection angle of 90 degrees, and may be set to other angles. Furthermore, the resistance wires 41, 51 that form the first and second mesh resistors 4, 5 do not necessarily have to be straight, but may be formed in a mesh shape that is curved or the like.

However, the pitch of the resistance wires 41, 51 of the first and second mesh resistors 4, 5 is not limited to 500 μm, but may be approximately 100 μm to 5 mm.

In addition, the inclination angle of the first and second mesh resistors 4, 5 is not limited to 22.5 degrees, and may be set to another angle, for example, any angle between 5 degrees and 85 degrees with respect to the horizontal direction X, as long as it does not interfere with the image of a liquid crystal panel or the like arranged on the back surface of the touch panel 1 and cause a moire pattern.

The first mesh resistor 4 formed on the first transparent substrate 2 and the second mesh resistor 5 formed on the second transparent substrate 3 are formed on the first transparent substrate 2 and the second transparent substrate 3 so that the pitch P of the thin resistance wires 41, 51 is shifted by 1/2 pitch (250 μm) when the first and second transparent substrates 2, 3 are combined, as shown in FIG. 5. The resistance value per unit area of the first and second mesh resistors 4, 5 is set to, for example, 400 to 2000 Ω/□.

In this way, by arranging the first mesh resistor 4 and the second mesh resistor 5 with a 1/2 pitch (250 μm) offset, it is possible to improve the transparency of the touch panel 1. However, the first mesh resistor 4 and the second mesh resistor 5 are not limited to being offset by 1/2 pitch, and may be arranged with an offset of about 1/5 to 1/2 as long as they do not overlap.

As described above, the first and second mesh resistors 4, 5 have a very thin line width W of 1 to 100 μm, so even if they are formed on one side of the first and second transparent substrates 2, 3, they cannot be visually recognized by humans, that is, they are not visible to the naked eye. Therefore, the pair of transparent substrates 2, 3 on which the first and second mesh resistors 4, 5 are formed has a very high aperture ratio of about 98%, and is recognized as transparent to the naked eye.

As shown in FIG. 7, a pair of first current-carrying portions 42, 43 in the form of narrow, elongated strips for conducting electricity to the first mesh resistor 4 are formed on both opposing (upper and lower) edges of the first transparent substrate 2. The first current-carrying portions 42, 43 are integrally formed on the upper and lower edges of the first transparent substrate 2 with the same material as the first mesh resistor 4 and connected to the resistance wire 41 of the first mesh resistor 4. The first mesh resistor 4 is for detecting the touch position in the Y direction.

The first mesh resistor 4 has a pair of first current-carrying electrodes 44, 45 for connecting one of the first current-carrying parts 42, 43 to a ground potential (0 V) and applying a required voltage Vcc to the other first current-carrying part 43. The first current-carrying electrodes 44, 45 are formed, for example, from a silver paste having excellent electrical conductivity.

Of the pair of first current-carrying electrodes 44, 45, one of the first current-carrying electrodes 44 is arranged in a state overlapping the first current-carrying portion 42, and includes a first current-carrying electrode portion 441 formed in a long, narrow strip shape that is wider than the first current-carrying portion 42, a vertical electrode portion 442 arranged vertically along the edge of the first transparent substrate 2 at one end (left end in FIG. 7) along the longitudinal direction of the first current-carrying electrode portion 441, a horizontal electrode portion 443 arranged across the center along the lower edge of the first transparent substrate 2 at the lower end of the vertical electrode portion 442, and a first extraction electrode portion 444 formed in a generally L-shape facing downward at the tip of the horizontal electrode portion 443.

Of the pair of first current-carrying electrodes 44, 45, the other first current-carrying electrode 45 is arranged in a state overlapping the first current-carrying portion 43 and includes a first current-carrying electrode portion 451 formed in a narrow strip shape slightly wider than the first current-carrying portion 43, and a second extraction electrode portion 452 formed in a generally L-shape facing downward at the center along the longitudinal direction of the first current-carrying electrode portion 451.

Furthermore, the first and second lead electrode portions 451, 452 are provided with third and fourth lead electrode portions 544, 554 adjacent to each other at a required interval, as described below, for connection to the second current-carrying electrode portion 551 of the second mesh resistor 5. The upper ends of the third and fourth lead electrode portions 544, 554 are integrally provided with connection portions 545, 555 formed in a tiny planar rectangular shape for connection to the second current-carrying electrode portion 543, 553 of the second mesh resistor 5. The connection portions 545, 555 of the third and fourth lead electrode portions 543, 553 have tiny holes drilled therein.

On the other hand, as shown in FIG. 8, a pair of second current-carrying portions 52, 53 in the form of narrow, elongated strips for conducting electricity to the second mesh resistor 5 are formed on both opposing (left and right) edges of the second transparent substrate 3. The second current-carrying portions 52, 53 are integrally formed on the left and right edges of the second transparent substrate 3 with the same material as the second mesh resistor 5 and connected to the electrode portion 51 of the second mesh resistor 5. The second mesh resistor 5 is for detecting the touch position in the X direction.

The first current-carrying parts 52, 53 of the second mesh resistor 5 are connected to a pair of second current-carrying electrodes 54, 55 for connecting one of the second current-carrying parts 52, 53 to ground potential (0 V) and applying a required voltage Vcc to the other second current-carrying part 53. The second current-carrying electrodes 54, 55 are formed, like the first current-carrying electrodes 44, 45, from, for example, a silver paste having excellent conductivity.

Of the pair of second current-carrying electrodes 54, 55, one second current-carrying electrode 54 is arranged in a state where it overlaps with the second current-carrying portion 52, and includes a second current-carrying electrode portion 541 formed in a long and narrow strip shape that is wider than the second current-carrying portion 52, a lateral electrode portion 542 arranged at the lower end of the second current-carrying electrode portion 541 along the lower edge of the second transparent substrate 3 to the center, and a connection portion 543 formed in a tiny planar rectangular shape at the tip of the lateral electrode portion 542. A small circular opening is provided at the center of the connection portion 543. The connection portion 543 is arranged at a position corresponding to the connection portion 545 described above.

The other second current-carrying electrode 55 of the pair of second current-carrying electrodes 54, 55 is arranged in a state where it overlaps with the second current-carrying portion 53, and includes a second current-carrying electrode portion 551 formed in a long and narrow strip shape wider than the second current-carrying portion 53, a lateral electrode portion 552 arranged at the lower end of the second current-carrying electrode portion 551 along the lower edge of the second transparent substrate 3 to the center, and a connection portion 553 formed in a tiny planar rectangular shape at the tip of the lateral electrode portion 552. A small circular opening is provided at the center of the connection portion 553. The connection portion 553 is arranged at a position corresponding to the above-mentioned connection portion 555.

The flexible printed circuit board 10 for energizing the first and second mesh resistors 4 and 5 is attached to the first transparent substrate 2 as described above. Therefore, the connection parts 543 and 553 for energizing the second mesh resistor 5 provided on the second transparent substrate 3 must be electrically connected to the connection parts 545 and 555 of the lead-out parts 544 and 554 provided on the first transparent substrate 2.

The connection parts 543, 553 for passing electricity through the second mesh resistor 5 provided on the second transparent substrate 3 are electrically connected to the connection parts 545, 555 of the lead parts 544, 554 provided on the first transparent substrate 2 by the approximately spherical conductive particles 16 as shown in FIG. 9. At that time, the conductive particles 16 are positioned and connected by the minute holes provided in the connection parts 543, 553 and the connection parts 545, 555.

As shown in Figures 3 and 4, the spacer members 6 are formed on the second transparent substrate 3 with an insulating material such as photoresist into a roughly hemispherical shape with a radius of about 3 μm so that they protrude about 3 μm from the surface of the second mesh resistor 5. The spacer members 6 are arranged so that they are spaced apart from each other by about 10 mm in the vertical and horizontal directions. The spacing at which the spacer members 6 are arranged may be smaller or larger than 10 mm, as long as it is possible to keep the first and second mesh resistors 4, 5 apart.

As shown in FIG. 10, the flexible printed circuit board 10 is configured by forming four electrodes 102-105 for energizing the first and second mesh resistors 4, 5 of the touch panel 1 in approximately parallel relation on the surface of a planar, approximately T-shaped insulating substrate 101 having flexibility made of synthetic resin or the like. The tips 102a-105a of the four electrodes 102-105 are formed wide at the tip of the insulating substrate 101 at a required interval. The tips 102a-105a of the four electrodes 102-105 of the flexible printed circuit board 10 are connected to the first to fourth extension parts 444, 452, 544, 555 of the touch panel 1 (see FIG. 7) by soldering or other means. The first and second mesh resistors 4, 5 of the touch panel 1 are connected at both ends to the detection circuit 7 via the flexible printed circuit board 10.

The detection circuit 7 applies a required voltage Vcc to both ends of the first and second mesh resistors 4, 5 in the touch panel 1 to energize them, and detects the resistance value between the first and second mesh resistors 4, 5 as a voltage value at the first and second electrodes 4, 5, thereby detecting the position where the first transparent substrate 2 located on the surface of the touch panel 1 is touched.

The detection circuit 7 can be the same as the detection circuit of the touch panel 1 made of a conventional ITO film, and its description is omitted here.

<Function of touch panel>
In the touch panel according to the first embodiment, it is possible to provide a transparent touch panel of an analog resistive film type capable of detecting a touch position without using a transparent electrode film made of ITO (Indium Tin Oxide) in the following manner.

That is, as shown in FIG. 1, the touch panel 1 according to the first embodiment includes first and second transparent substrates 2 and 3 arranged to face each other with a small gap therebetween, and first and second mesh resistors 4 and 5 formed in a mesh shape made of thin metal wires on the facing surfaces of the first and second transparent substrates 2 and 3 so as not to be visible to the naked eye.

The first and second mesh resistors 4, 5 are constructed by forming very thin strip-shaped (fine wire) resistance wires 41, 51 made of titanium (Ti) into a mesh shape. Therefore, the first and second mesh resistors 4, 5 are transparent electrodes that cannot be seen with the naked eye.

Experimental Example 1
The present inventors fabricated a prototype touch panel 1 as shown in Fig. 1 and conducted an experiment to measure the light transmittance (transparency) and color of the touch panel 1. The first and second mesh resistors 4, 5 were made of very thin strip-shaped (thin wire) resistance wires 41, 51 made of titanium (Ti) with a film thickness T of 800 Å and a line width W of 5 μm, which were formed in a mesh shape with a pitch of 500 μm. As Comparative Example 1, a touch panel was used in which a thin film made of ITO was formed to a uniform thickness (150 Å) on the opposing surfaces of a pair of transparent glass substrates.

Figures 12 to 14 are charts and graphs showing the measurement results of the above Experimental Example 1 and Comparative Example.

As is clear from Figures 12 to 14, the touch panel 1 of Experimental Example 1 exhibits a very high light transmittance of 80% across all wavelengths, and is recognized as transparent by the human eye.

On the other hand, the touch panel according to the comparative example has a low light transmittance of 60-70% in the short wavelength region, and the average transmittance is also slightly lower than that of touch panel 1 according to the present experimental example 1.

In addition, as shown in Figure 14, the touch panel 1 of Experimental Example 1 is colorless, whereas the touch panel using a thin film made of ITO has a yellowish tint.

Experimental Example 2
The present inventors also conducted an experiment to fabricate a prototype touch panel 1 as shown in Fig. 1 and measure the resistance value of the touch panel 1. The first and second mesh resistors 4 and 5 are the same as those in Experimental Example 1. As Comparative Example 2, a touch panel was used in which a thin film made of ITO was formed to a uniform thickness (150 Å) on the opposing surfaces of a pair of transparent glass substrates.

Figures 15 and 16 are charts and graphs showing the measurement results of Experimental Example 2 and Comparative Example 2.

Figure 15 shows the sheet resistance (resistance per unit area) of the first and second mesh resistors 4 and 5 of the touch panel 1 in Experimental Example 2. Note that the inter-terminal resistance in Figure 15 is calculated by sheet resistance (R) x current flow direction (Y) / current flow width direction (X).

As is clear from FIG. 15, in the touch panel 1 in experimental example 2, the sheet resistance (Ω/□) of the first and second mesh resistors 4, 5 is high at 785.2, and the resistance between the terminals is also high at 450 Ω, whereas in the transparent electrode film made of an ITO film in comparative example 2, the sheet resistance (Ω/□) fluctuates widely from 450 to 750, and the resistance between the terminals also fluctuates widely from 257.9 to 429.8 Ω, and in either case, it is clear that the characteristics are not stable.

Figure 16 shows the variation in the in-plane distribution of the resistance values of the first and second mesh resistors 4 and 5 of the touch panel 1 in Experimental Example 2. Note that Figure 16 shows data showing the in-plane variation in the resistance values of a uniform, so-called solid film before the first and second mesh resistors 4 and 5 made of titanium are meshed.

As is clear from FIG. 16, the touch panel 1 in Experimental Example 2 has a small sigma (σ) of 0.18 and 0.20, which indicates the variation in the in-plane distribution of the first and second mesh resistors 4 and 5, whereas the transparent electrode film made of an ITO film in Comparative Example 2 has a relatively large sigma (σ) of 22.64 and 23.91, which indicates the variation in the in-plane distribution, although the units are different from those in Experimental Example 2, indicating a large variation.

It is possible to provide a transparent touch sensor using an analog resistive film method that can detect the touch position without using an ITO (Indium Tin Oxide) film.

REFERENCE SIGNS LIST 1... touch panel 2... first transparent substrate 3... second transparent substrate 4... first mesh resistor 5... second mesh resistor 7... detection circuit

Claims (13)

A pair of transparent substrates arranged to face each other with a small gap therebetween;
a first mesh resistor and a second mesh resistor each formed in a mesh shape made of thin metal wires on the opposing surfaces of the pair of transparent substrates so as not to be visually recognized;
a spacer member provided on one of the pair of transparent substrates and configured to hold the first and second mesh resistors in a non-contact state;
a detection means for detecting a contact position of the first and second mesh resistors that is contacted by touching the transparent substrate disposed on the front side of the pair of transparent substrates as a change in resistance value by applying a voltage to both ends of the first and second mesh resistors, respectively;
A touch panel equipped with The touch panel according to claim 1, wherein the transparent substrate located on the front side of the pair of transparent substrates has a decorative portion on its outer periphery. The touch panel according to claim 1, wherein the first and second mesh resistors are formed in a mesh shape that intersects with a predetermined pitch and are offset from one another so as not to overlap. The touch panel according to claim 3, wherein the first and second mesh resistors are arranged parallel to each other with a pitch of 100 μm to 5 mm. The touch panel according to claim 1, wherein the first and second mesh resistors are formed as thin wires of a metal or alloy of either titanium (Ti) or chromium (Cr). The touch panel according to claim 5, wherein the first and second mesh resistors have a film thickness of 500 to 2000 Å and a line width of 1 to 100 μm. The touch panel according to claim 6, wherein the first and second mesh resistors have a resistance per unit area of 400 to 2000 Ω/□. The touch panel according to claim 1, wherein the pair of transparent substrates are made of tempered glass, and the transparent substrate located on the front side of the pair of transparent substrates also serves as a cover glass. The touch panel according to claim 8, wherein the transparent substrate located on the front side of the pair of transparent substrates is made of a glass plate having a thickness of 0.1 to 0.5 mm, and the transparent substrate located on the rear side is made of a glass plate having a thickness of 0.5 to 3.0 mm. a pair of first current-carrying electrodes for passing current through the first mesh resistor are formed on both opposing edges of one of the pair of transparent substrates, and a pair of second current-carrying electrodes for passing current through the second mesh resistor are formed on both opposing edges of the other transparent substrate that are different from the edges of the first mesh resistor;
The touch panel according to claim 1 , wherein the first and second current-carrying electrodes are extended to positions of current-carrying terminals provided on parts of outer peripheries of the pair of transparent substrates. The touch panel according to claim 10, wherein the current-carrying terminal is provided on the transparent substrate located on the front side of the pair of transparent substrates, and the lead-out portion of one current-carrying electrode provided on the transparent substrate located on the back side of the pair of transparent substrates is connected to the current-carrying terminal provided on the transparent substrate located on the front side via a conductive member when the pair of transparent substrates are arranged to face each other with a small gap between them. The touch panel according to claim 1, wherein the pair of transparent substrates are formed to have the same shape. The touch panel according to claim 1, wherein the transparent substrate located on the back side of the pair of transparent substrates has an opening for attaching a flexible printed circuit board for passing electricity through the first and second mesh resistors.

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