JP6995313B2 - Patternless touch panel - Google Patents

Description

The present invention relates to a patternless touch panel, and more particularly to a patternless touch panel provided with a conductive sheet preferably used for the patternless touch panel.

Patent Documents 1 to 3 disclose a patternless touch panel in which electrodes are provided on four sides of a transparent conductive film and an AC voltage for position detection having the same phase and the same potential is supplied. Specifically, in Patent Document 1, four waveform detection circuits are provided corresponding to the electrodes at the four corners of the conductive film, and the coordinate positions are calculated based on the output voltage of the detection circuits. Further, in Patent Document 2, pulse signals having the same phase and the same voltage are applied to the electrodes at the four corners of the rectangular conductive film, and the user's touch position is detected using the logarithmic signal ratio. Further, in Patent Document 3, the resolution is increased by using an arithmetic method using non-linear data. In these touch panels, it is not necessary to form a fine transparent electrode pattern on the conductive sheet, and a conductive sheet in which conductive layers are uniformly laminated is used.

International Publication WO 2013/153609 Pamphlet Japanese Unexamined Patent Publication No. 2013-250642 JP-A-2015-201223

The inventors of the present application prototyped a conductive sheet applicable to the patternless touch panel described in the above document, and conducted an evaluation test of the patternless touch panel on which the conductive sheet was mounted. In this evaluation test, a conductive sheet in which a uniform conductive layer was formed on the entire one surface of the insulating film and wiring was formed on the conductive layer via an insulating film was used. As a result, there was room for improvement in terms of touch position detection accuracy.

Therefore, an object of the present invention is to provide a patternless touch panel having good detection accuracy.

In order to achieve the above object, in the patternless touch panel according to the present invention, a conductive sheet in which a signal input layer is uniformly formed in the detection region on the back surface of the substrate and the detection layer is uniformly formed in the detection region on the front surface of the substrate is provided. Using. Then, the signal detection unit gives a measurement signal to the first signal input node provided in the signal input layer, and an object approaching the detection layer based on the difference information of the output signal output from the pair node provided in the detection layer. Changed to calculate the position of.

That is, the patternless touch panel according to one aspect of the present invention is uniformly formed in the detection region including the sheet-like substrate having an insulating property and the central portion on the back surface side of the substrate, and the first signal is input to the peripheral portion. A conductive signal input layer provided with nodes and a plurality of signal output nodes uniformly formed in the detection region on the surface side of the substrate and separated from each other at the peripheral edge portion. A measurement signal is given to the conductive sheet having the detection layer and the first signal input node, and based on the difference information of the output signals output from the paired node selected from the plurality of signal output nodes. It is characterized by including a position detection unit that calculates the position of an object close to the detection layer.

Here, the "sheet" includes a sheet formed in the form of a thin plate and a sheet formed in the form of a film thinner than the thin plate. The same applies to the case of "sheet-like", which is a concept including thin plate-like and film-like.

In the above-mentioned patternless touch panel, the inventors of the present application are provided with a signal input layer in which a signal input node for inputting a measurement signal is provided on the front surface of an insulating substrate, and a signal output node separated from each other on the back surface of the substrate. It was found that good detection accuracy was obtained by using a conductive sheet in which each of the detection layers was uniformly formed for a patternless touch panel. Specifically, since the signal input layer and the detection layer are separated via an insulating substrate, it is possible to prevent signal interference between the signal input node and the signal output node. can.

In the patternless touch panel of the above aspect, the surface-side conductive layer may be uniformly formed by laminating in the detection region on the surface of the detection layer via an insulating layer. Further, the surface-side conductive layer may be provided with a second signal input node for receiving the measurement signal.

This makes it possible to realize a patternless touch panel having good detection accuracy even in a noisy environment.

In the patternless touch panel of the above embodiment, on the surface of the substrate, a wiring region in which an output wiring connected to the signal output node is formed is provided around the detection layer, and the first signal input node is provided with a wiring region. The input wiring formed on the back surface of the substrate may be connected so as to be a region that overlaps with the wiring region in a plan view and does not overlap with the output wiring.

As a result, it is possible to avoid an inter-wiring capacitance between the input wiring and the output wiring, and it is possible to realize a patternless touch panel having good detection accuracy.

In the patternless touch panel of the above aspect, the thickness of the substrate may be larger than the thickness of the insulating layer.

As a result, it is possible to increase the change in the potential related to the touch operation, and it is possible to improve the detection accuracy of the touch position.

In the patternless touch panel of the above aspect, the detection layer is uniformly formed in a rectangular detection region, and the signal output nodes are at least two locations on each side of the detection region so as to be separated from each other. It is provided.

As a result, it is possible to obtain a patternless touch panel having good touch position detection accuracy and good temporal stability.

As described above, according to the present invention, it is possible to obtain a patternless touch panel having high position detection accuracy.

It is a top view which shows typically the conductive sheet for the patternless touch panel which concerns on embodiment. FIG. 3 is a schematic cross-sectional view taken along the line II-II of FIG. It is a top view which shows typically the ground layer and the 2nd input wiring. It is a top view which shows typically the detection layer and the output wiring. It is a top view which shows typically the signal input layer and the 1st input wiring. It is a figure for demonstrating the position detection principle of the touch panel which applied the conductive sheet. It is a figure which showed an example of the signal waveform when the point TP of FIG. 6 is touched. It is a figure which shows the schematic structure of the patternless touch panel. It is a top view which shows the divided area which divided the detection area of a conductive sheet. It is a figure which shows the relationship between the touch position of a two-point touch and a peak voltage. It is a figure which shows the relationship between the touch position of a two-point touch and a peak voltage. It is a top view which shows the other example of a conductive sheet.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The following description of preferred embodiments is merely exemplary and is not intended to limit the invention, its applications or its uses.

As shown in FIG. 8, the patternless touch panel includes a conductive sheet 1 and a position detection unit 6 that calculates the position of an object close to the detection layer 31 of the conductive sheet 1.

<Conductive sheet>
FIG. 1 is a plan view schematically showing a conductive sheet according to an embodiment. Further, FIG. 2 is a schematic cross-sectional view taken along the line II-II of FIG. In FIG. 1, the detection layer 31 and the output wiring 53 are shown by a solid line, and the ground layer 33 and the second input wiring 52 are shown by a broken line.

The conductive sheet 1 is arranged on the front side or the rear side of a display device (for example, a liquid crystal device) that displays a display screen that functions as a touch panel. That is, the conductive sheet 1 according to the present embodiment can function regardless of whether it is placed in front of or behind the display device.

As shown in FIGS. 1 and 2, the conductive sheet 1 according to the embodiment has a sheet-shaped (film-shaped or thin plate-shaped) substrate 2.

On the surface of the substrate 2, in the rectangular detection region Rd including the central portion thereof, the detection layer 31, the insulating layer 32, and the grounding layer 33 as the surface-side conductive layer are uniformly arranged in order from the one closest to the substrate 2. It is formed and laminated. Similarly, on the back surface of the substrate 2, the signal input layer 41 is uniformly formed in the detection region Rd. The detection region Rd corresponds to a region for detecting the touch position when the conductive sheet 1 is used as a member of the patternless touch panel. In this embodiment, it is assumed that the surface of the substrate 2 faces the operator. Further, "front" refers to the operator side, and "rear" refers to the opposite side.

Hereinafter, each configuration of the conductive sheet 1 will be described in detail.

-Hypokeimenon-
When the conductive sheet 1 is used as a member of a patternless touch panel, the substrate 2 is preferably made of an insulating material from the viewpoint of preventing a short circuit due to contact between another member and the conductive layer 2. The substrate 2 according to the present embodiment includes a substrate 21 having a predetermined thickness and an insulating film 22 attached to the surface of the substrate with an adhesive film (for example, an OCA (Optical Clear Adhesive) film).

The material of the substrate 21 may be any material having an insulating property, and is not particularly limited. For example, a hard plate such as alumina or a glass cloth impregnated epoxy resin “so-called FR4 (Flame Retardant Type 4) substrate”, made of resin. One or more materials selected from the group consisting of films and rubber materials (preferably flexible) can be used. Above all, an FR4 substrate having a low dielectric constant is desirable from the viewpoint of reducing the capacitance between the detection layer 31 and the signal input layer 41. Specific examples of the resin film include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), cycloolefin polymer (COP), polycarbonate (PC), polyimide (PI), polyvinyl chloride (PVC), and triacetate. Examples thereof include triacetyl cellulose (TAC), and PET film is more preferable from the viewpoint of heat resistance and cost. Since these films contain a plasticizer, they have some flexibility and can exhibit their functions even if they are not rubber materials.

The thickness of the substrate 21 is determined from the viewpoint of obtaining good signal propagation performance between the signal input layer 41 and the detection layer 31, for example, the touch capacitance value and the touch position formed between the signal input layer 41 and the detection layer 31. It is determined based on the impedance and the like from the position detection unit 6 to the position detection unit 6. If the thickness of the substrate 21 is not sufficiently secured, in the position detection unit 6 (see FIG. 8), when the capacitance between the signal input layer 41 and the detection layer 31 is relatively large with respect to the touch capacitance, Sufficient output signal may not be obtained. Specifically, it is preferable that the thickness of the substrate is 0.2 mm or more and 6.8 mm or less.

Specifically, the insulating film 22 is, for example, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), cycloolefin polymer (COP), polycarbonate (PC), polyimide (PI), polyvinyl chloride (PVC), triacetate. , Triacetyl cellulose (TAC) and the like, and in particular, a PEN film is more preferable from the viewpoint of heat resistance and cost. The thickness of the insulating film 22 is not particularly limited, but is preferably sufficiently thinner than that of the substrate 2 from the viewpoint of avoiding bonding stress, and is, for example, 10 μm to 200 μm.

Further, when the conductive sheet 1 is arranged on the front side of the above-mentioned display device, it is desirable that the substrate 2 has high light transmission (for example, transparent) from the viewpoint of ensuring visibility. On the other hand, when the conductive sheet 1 is arranged on the rear side of the display device, the substrate 2 does not need to have high transparency (for example, is transparent) and may be colored.

-Detection layer-
On the surface of the substrate 2, the detection layer 31 is uniformly formed in the rectangular detection region Rd, and a plurality of output wirings 53 are formed in the wiring region Rw surrounding the detection region Rd. The detection region Rd corresponds to a region for detecting the touch position when the conductive sheet 1 is used as a member of the patternless touch panel. In other words, the conductive sheet 1 of the present invention is configured to be mounted on a patternless touch panel so that the presence or absence of a touch operation can be detected by the position detection unit 6 (see FIG. 8). The detection layer 31 is uniform in the detection layer forming region R1 slightly wider than the detection region Rd from the viewpoint of avoiding the generation of capacitance between the electrode E or the output wiring 53 and the signal input layer 41 or the ground layer 33. It is desirable that it is formed in. Even in this case, it can be said that the detection layer 31 is uniformly formed in the detection region Rd.

On each side of the detection layer 31 (corresponding to the peripheral edge), a plurality of electrodes E (corresponding to the signal output node No.) at equal pitches at intermediate positions in the longitudinal direction of the sides at predetermined intervals from the corners of each side. Is formed. The number of electrodes E and the number of output wirings 53 in the wiring area described later are equal to each other. FIG. 1 shows an example in which three electrodes E are provided on each side of the conductive layer 22. In addition, in this embodiment, "equal" may be substantially equal, and the same effect can be obtained even if there is some misalignment. Therefore, "equal" is a concept that includes approximately equality in addition to equality (perfect match).

In the present embodiment, the touch operation is a concept including an operation of directly touching the touch panel and a hovering operation. Further, performing the above-mentioned "touch operation" is referred to as "touching". Further, the position on the conductive layer 2 corresponding to the position of the indicator (for example, the finger of the operator) when the "touch operation" is performed is referred to as the "touch position".

The detection layer 31 includes carbon, silver, copper, aluminum, indium tin oxide (ITO), fluorine-doped tin oxide (FTO), metal-doped zinc oxide, metal nanowires, antimonated tin oxide (ATO), polythiophene (PEDOT), and the like. It contains one or more conductive materials selected from the group consisting of polyaniline and water-soluble sulfonated polyaniline. The carbon is not particularly limited as long as it exhibits conductivity, and for example, carbon black, graphene, and carbon nanotubes can be used.

The conductive material used for the detection layer 31 may be used at the same time as the synthetic resin serving as a binder for the purpose of improving the adhesion to the substrate 2. Further, from the viewpoint of processability, it is desirable to use a mixed solution of a synthetic resin in which a conductive material is dispersed and a volatile solvent. The synthetic resin used as the binder is not particularly limited, but a polyester resin, an acrylic resin, a polyurethane ester resin, or an epoxy resin having moisture and heat resistance is desirable from the viewpoint of stability over time. Specifically, the solubility in water of polyester resin, fluororubber, diene rubber, styrene rubber, nitrile rubber, acrylic rubber, butyl rubber, thiocol, fluororesin, polyolefin resin, acrylic resin, nitrile resin, etc. is 1%. Less than the resin can be preferably used. The conductive layer may contain a cross-linking agent.

(Resistance value of detection layer)
The detection layer 31 preferably has a resistance value of 1 kΩ / □ or more in small and medium-sized applications (for example, tablet PCs) from the viewpoint of obtaining a conductive sheet 1 having excellent detection accuracy and excellent stability over time. .. When the resistance value is less than 1 kΩ / □, the peak time generated by the differential potential of the detection currents from the two electrodes becomes small, so that it becomes indistinguishable from noise when the position detection unit 6 detects the touch position. There is a risk that it will end up. On the other hand, in a large-scale application (for example, a large panel), the resistance from the touch position to the electrode E of the detection layer 31 becomes high, so that the lower limit resistance value of 50 Ω / □ or more is sufficient. Further, the resistance value of the detection layer 31 is preferably 10 MΩ / □ or less in both small and medium-sized and large-sized applications. If the resistance value exceeds 10 MΩ / □, the position detection unit 6 may detect the touch position, which may cause a delay as well as a decrease in sensitivity due to a decrease in output due to the resistance.

(Variation of resistance value of detection layer)
The variation in the resistance value of the detection layer 31 is preferably 20% or less from the viewpoint of obtaining the stability of the detection accuracy. By suppressing the variation in resistance value within the above range, it is possible to realize the conductive sheet 1 having stable and good detection accuracy regardless of the location on the detection layer 31.

(Thickness of detection layer)
The thickness of the detection layer 31 is preferably 0.1 μm or more and 40 μm or less, more preferably 0.5 μm or more and 5 μm, from the viewpoint of obtaining a sufficient resistance value as the conductive sheet 1 for the patternless touch panel. It is as follows.

It is desirable that the thickness of the detection layer 31 is uniform. Here, "the thickness of the detection layer 31 is uniform" means that the variation in the thickness of the detection layer 31 is 20% or less of the average thickness. Since the thickness of the detection layer 31 is uniform, the variation in the resistance value of the detection layer 31 is reduced, stable detection accuracy can be obtained, and stability over time can be improved.

(Translucency of detection layer)
When the conductive sheet 1 is arranged on the front side of the above-mentioned display device (not shown), the detection layer 31 of the conductive sheet 1 may be formed of a highly transparent conductive material from the viewpoint of ensuring the visibility of the display screen. desirable.

On the other hand, when the conductive sheet 1 is arranged on the rear side of the display device, it is not necessary to consider the influence on the visibility of the display screen, and the detection layer 31 can be formed of a conductive material having low transparency. be. Specifically, the total light transmittance of the conductive sheet 1 can be preferably less than 80%, more preferably 70% or less, and particularly preferably 50% or less.

-Output wiring-
A plurality of output wirings 53 extending along the peripheral edge of the detection layer 31 are formed in the wiring region Rw on the surface of the substrate. The output wiring 53 is used for acquiring the current output from the electrode E as the signal output node No. of the detection layer 31. In other words, each output wiring 53 is connected to the detection layer 31 via an electrode E provided so as to be separated from each other, and this electrode E acts as a signal output node. Further, each output wiring 53 is routed along the peripheral edge of the detection layer 31, gathered at one place (near the lower right corner in FIG. 1), and connected to different electrodes E, respectively. By consolidating the ends (electrodes) of the output wiring 53 in this way, it becomes easy to connect to the position detection unit 6.

The material of the output wiring 53 is not particularly limited, but known metal wires such as gold, silver, copper, and aluminum, metal foil, and conductive paste can be used. From the viewpoint of the adhesion between the output wiring 53 via the electrode E and the detection layer 31, the output wiring 53 is preferably a conductive paste. The conductive substance contained in the conductive paste is not particularly limited, but may be carbon powder, silver powder, copper powder, resin core metal plating powder, aluminum powder, or a mixed powder thereof, and the shape thereof is not particularly limited. For example, it may be spherical or flaky.

(Resistance value of output wiring)
The resistivity of the output wiring 53 is preferably 1 × 10 ^-4 Ω · cm or less in order to obtain a higher detection voltage. When the resistivity of the output wiring exceeds 1 × 10 ^-4 Ω · cm, the voltage drop due to the output wiring 53 becomes large, and the voltage drops more than necessary for the signal input nodes Ni (second and third electrodes E2 and E3) described later. May have to be applied.

(Size of output wiring and spacing from conductive layer)
The line width of the output wiring 53 is not particularly limited, but is preferably 10 μm or more and 1000 μm or less, and more preferably about 300 μm, from the viewpoint of workability. If the line width of the output wiring 53 is less than 10 μm, the workability is remarkably lowered, and there is a possibility that the output wiring 53 is broken or the resistance value of the wiring region Rw is increased. Further, if the line width of the output wiring 53 exceeds 1000 μm, the capacity of the wiring region Rw that is not involved in the detection of the touch position may increase.

The thickness of the output wiring 53 is not particularly limited, but is preferably 3 μm or more and 20 μm or less from the viewpoint of workability. If the thickness of the output wiring 53 is less than 3 μm, there is a risk that the wiring may be broken or the resistance value may increase due to handling. Further, if the thickness of the output wiring 53 exceeds 20 μm, the workability may be significantly deteriorated due to an increase in viscosity, the need for double coating, and the like.

Further, the output wiring 53 may be wired away from the detection layer 31 and other output wiring 53 except for the connection portion (electrode E) with the detection layer 31 as shown in FIG. Preferably, the distance between the detection layer 31 and the output wiring 53 is 200 μm or more. This makes it possible to prevent noise from being superimposed on the output wiring 53.

-Ground layer (conducting layer on the surface side)-
As shown in FIG. 2, on the surface side of the detection layer 31 and the output wiring 53, the conductive grounding layer 33 is uniformly formed by laminating via the insulating layer 32.

The insulating layer 32 can be made of, for example, an insulating film attached with an adhesive film. Since the material and thickness of the insulating film constituting the insulating layer 32 can be set in the same way as the insulating film constituting the substrate 2, detailed description thereof will be omitted here.

As shown in FIG. 3, the ground layer 33 is uniformly formed in the ground layer forming region R2 having substantially the same size as the detection region Rd. That is, the formation range of the ground layer 33 is formed so as to be slightly narrower than that of the detection layer 31 and not to overlap with the electrode E of the detection layer 31 in a plan view. As a result, it is possible to prevent a capacitance from being generated between the electrode E of the detection layer 31 and the ground layer 33, and it is possible to improve the detection accuracy of the touch position. In FIG. 3, the ground layer 33 and the second input wiring 52 are shown by a solid line, and the detection layer 31 is shown by a broken line.

The resistivity of the ground layer 33 is preferably low, for example, the resistivity is preferably 1 × 10 ^-4 Ω · cm or less. Further, the ground layer 33 is preferably a metallic conductor containing at least one selected from the group consisting of copper, aluminum and iron. For example, copper, aluminum, iron, or alloys thereof. When soldering the second input wiring 52 to the ground layer 33, it is preferable to use copper as the ground layer 33.

A signal input node Ni is provided at an intermediate position on the upper side (corresponding to a peripheral portion) of the ground layer 33 on the left-right side of the drawing. A second input wiring 52 wider than the output wiring 53 is connected to the signal input node Ni. The second input wiring 52 extends in the upward direction of the drawing of FIG. 3, and then extends in an L shape along the peripheral edge of the substrate 2 to an intermediate position in the vertical direction of the right side toward the right side of the drawing and the downward direction of the drawing. .. A pattern generator PG of a position detection unit 6, which will be described later, is connected to the tip of the second input wiring 52. Then, the measurement signal from the pattern generator PG is supplied to the signal input node Ni via the second input wiring 52. The material, resistance value, and thickness of the second input wiring 52 may be set in the same manner as the output wiring 53, and detailed description thereof will be omitted here. The line width of the second input wiring is not particularly limited, but is preferably 10 μm or more and 1000 μm or less, for example.

-Signal input layer-
As shown in FIG. 2, a signal input layer 41 is formed on the back surface of the substrate 2. As shown in FIGS. 4 and 5, the signal input layer 41 is uniformly formed in the signal input layer forming region R3 having substantially the same size as the detection region Rd. The ground layer 33 and the signal input layer 41 are arranged so that their positions in the conductive sheet 1 in a plan view are substantially the same. In FIG. 4, the detection layer 31 and the output wiring 53 are shown by a solid line, and the signal input layer 41 and the first input wiring 51 are shown by a broken line. Further, in FIG. 5, the signal input layer 41 and the first input wiring 51 are shown by a solid line, and the detection layer 31 is shown by a broken line.

As shown in FIG. 5, a signal input node Ni is provided at an intermediate position on the upper side (corresponding to a peripheral portion) of the signal input layer 41 on the left-right side of the drawing. A first input wiring 51 wider than the output wiring 53 is connected to the signal input node Ni. The first input wiring 51 and the second input wiring 52 are arranged so that their positions in the conductive sheet 1 in a plan view are substantially the same. Specifically, the first input wiring 51 extends in the upward direction of the drawing of FIG. 5, and then L-shapes along the peripheral edge of the conductive sheet toward the right side of the drawing and the downward direction of the drawing, in the vertical direction on the right side of the drawing. It extends to the middle position. A pattern generator PG of a position detection unit 6, which will be described later, is connected to the tip of the first input wiring 51. Then, similarly to the second input wiring 52, the measurement signal from the pattern generator PG is supplied to the signal input node Ni via the first input wiring 51.

Here, as shown in FIG. 4, the first input wiring 51, the second input wiring 52, and the output wiring 53 are formed so as not to overlap each other in a plan view. As a result, it is possible to avoid the generation of inter-wiring capacitance between the first input wiring 51 and the output wiring 53 and between the second input wiring 52 and the output wiring 53.

The signal input layer 41 preferably has a low resistivity, and for example, the resistivity is preferably 1 × 10 ^-4 Ω · cm or less. Further, the signal input layer 41 is preferably a metallic conductor containing at least one selected from the group consisting of copper, aluminum, and iron. For example, copper, aluminum, iron, or alloys thereof.

Further, as shown in FIGS. 2 and 4, a ground wiring 42 is formed on the back surface of the substrate 2 at a position overlapping the output wiring 53 in a plan view. The ground wiring 42 extends so as not to be electrically and mechanically connected to the signal input layer 41 and the first input wiring 51 and to surround the signal input layer 41. By providing the ground wiring 42 on the back surface side of the output wiring 53 in this way, the impedance between the output wiring 53 and the ground wiring 42 can be matched to a desired value (for example, about 50Ω). ..

-Insulation cover layer-
As shown in FIG. 2, the front surface of the ground layer and the back surface of the signal input layer 41 may be covered with an insulating cover layer.

Specifically, in the example of FIG. 2, the insulating film 34 is attached to the surface of the ground layer 33 with an adhesive film (for example, an OCA (Optical Clear Adhesive) film). As the insulating film 34, the same insulating film 22 as the insulating film 22 constituting the substrate 2 can be used, and therefore the detailed description thereof will be omitted here.

Further, a solder resist 43 is applied to the back surface of the signal input layer 41. The material and thickness of the solder resist 43 are not particularly limited, and general-purpose products according to the prior art can be applied.

For example, when a space is provided in front of and behind the conductive sheet 1, insulating parts are arranged, or when the conductive sheet 1 is covered with a housing or the like, the insulating cover layer is not provided. You may.

<Position detector>
As shown in FIG. 8, the position detection unit 6 is differential with a pulse generator PG that gives a measurement signal to the signal input node Ni and two analog switches 61 and 61 (denoted as AS in FIG. 8) having the same configuration. It includes an amplifier 62, a noise filter 63, a peak hold unit 64, an analog-to-digital conversion circuit 65 (denoted as ADC in FIG. 8), and a calculation unit 66.

The analog switches 61 and 61 pass output signals from two electrodes E1 and E2 (hereinafter referred to as pair electrodes) to be measured arbitrarily selected from the electrodes E provided on the detection layer 31. The differential amplifier 62 outputs a differential signal indicating a signal amount difference between the output signals from the analog switches 61 and 61. The noise filter 63 removes the noise component of the differential signal output from the differential amplifier 62. The peak hold unit 64 holds the peak voltage of the differential signal from which noise has been removed as an analog signal. The analog-to-digital conversion circuit 65 converts the peak voltage value and the code information of the peak voltage into digital values based on the peak voltage (analog signal) generated by the peak hold unit 64.

The calculation unit 66 is configured to control the operation of each block of the position detection unit 6. For example, the calculation unit 66 selects pair electrodes E1 and E2 (corresponding to pair nodes) from the electrodes E provided on the detection layer 31, and sets the electrode selection signals SC1 indicating the pair electrodes E1 and E2 to two analog switches 61. , 61. Further, the arithmetic unit 66 determines the position of an object (for example, a user's finger) that has approached or touched the detection layer 31 based on the difference information included in the differential signal (digital value) output from the analog-to-digital conversion circuit 65. Is calculated by calculation. Here, the difference information refers to all the information obtained based on the differential signal. For example, the difference information includes code information indicating whether the differential signal is a positive voltage signal or a negative voltage signal, voltage difference information indicating the magnitude of the differential signal, and until the differential signal reaches a predetermined voltage. Includes time information, etc. Further, the arithmetic unit 66 includes a storage unit (not shown) in which a ROM in which a program for performing the above control is stored is stored.

<Touch panel position detection principle>
Hereinafter, the principle of detecting the touch position related to the touch operation of the patternless touch panel using the conductive sheet 1 will be specifically described. FIG. 6 is a schematic view showing a state in which the pulse generator PG of the position detection unit 6 and the differential amplifier 62 are connected to the conductive sheet 1 in the patternless touch panel using the conductive sheet 1. In FIG. 6, Z indicates the impedance between the signal input layer 41 and the detection layer 31 and the impedance between the detection layer 31 and the ground layer 33. This impedance Z is matched to a predetermined value (for example, about 50Ω). Note that in FIG. 6, the analog switches 61 and 61 are not shown.

In FIG. 6, the pulse generator PG is connected to the signal input node Ni of the signal input layer 41 via the input resistor Ria. Further, an input resistor Rib is connected between the signal input node Ni of the signal input layer 41 and the signal input node Ni of the ground layer 33, and the signal input node Ni of the ground layer 33 is grounded.

Then, when a measurement signal is given from the pulse generator PG to the signal input node Ni, the measurement signal is propagated to the detection layer 31 via the substrate 21 and output as an output signal from the electrode E of the detection layer 31. The differential amplifier 62 is given the output signals output from the pair electrodes E1 and E2 via the analog switches 61 and 61. After that, the calculation unit 66 (see FIG. 8) connected to the subsequent stage calculates the touch position.

Specifically, when a pulse signal is supplied to the signal input node Ni in the state where the touch position TP is touched, the touch position is charged up, and the pair electrodes E1 and E2 correspond to the following equations (1), respectively. The voltage is output.

V = Vdd (1-exp (-t / RC)) ... (1)

_C = _CT + CS (2)

Here, the equation (2) shows the value of C in the equation (1). In the formula (2), _CT is the capacitance between the touched finger and the detection layer 31, and CS is the capacitance inside the conductive sheet 1 at the touch position _TP . It is desirable that Cs is set so that the value of Ct / Cs is about 1 to 100.

Further, R in the equation (1) includes _R1 and _R2 which are resistance values between the electrodes E1 and E2 constituting the pair electrode and the touch position, and the electrodes E1 and E2 to the position detecting device 6. The wiring resistance _RL and the resistance component R _Z of the impedance Z between the signal input layer 41 and the detection layer 31 are included. However, since the wiring resistance _RL and the resistance component R _Z can be made small to the extent that there is almost no effect, in the following calculation, the wiring resistance _RL and the resistance component R _Z are assumed to be “0 (zero)”.

Then, assuming that the resistance between one of the pair electrodes E1 and the touch position TP is _R1 , the voltage represented by the following equation (3) is output to each of the electrodes E1.

V ₁ = Vdd (1-exp (-t / R ₁ C)) ... (3)

Similarly, assuming that the resistance between the other electrode E2 of the pair electrodes and the touch position TP is _R2 , the voltage represented by the following equation (4) is output to each of the electrodes E2.

V ₂ = Vdd (1-exp (-t / R ₂ C)) ... (4)

Therefore, the differential amplifier 42 outputs the differential signal shown in the following equation (5) (the difference signal of the equations (3) and (4)).

Vdf = V ₁ -V ₂
= Vdd (-exp (-t / R ₁ C) + exp (-t / R ₂ C)) ... (5)

FIG. 7 is a diagram showing an example of an output signal of the pair electrodes E1 and E2 and a differential signal output from the differential amplifier 42 when the touch position TP is touched by the user. In FIG. 7, the vertical axis is the voltage value and the horizontal axis is the time. Further, FIG. 7 (a) shows the signal waveforms of V ₁ and V ₂ obtained by the formulas (1) and (2) described later, and FIG. 7 (b) shows the signal waveforms of V _df obtained by the formula (3). The signal waveform is shown.

Then, in the calculation unit 66 of the position detection unit 6, since the sign, magnitude, etc. (hereinafter referred to as differential signal information) of the differential signal represented by the equation (5) differ depending on the touch position, the differential signal. The touch position can be calculated based on the information.

The amplitude of the voltage detected by the position detection unit 6 differs depending on the type of touch operation (operation in which the indicator directly touches the touch panel and hovering operation), but the basic detection principle is irrespective of the type of touch operation. It is the same. Similarly, when the touch position is 1 point (so-called 1-point touch), when the touch position is 2 points (so-called 2-point touch), and when the touch position is 3 points or more (so-called multi-touch), the position is detected. The amplitude of the voltage detected by the unit 6 is different, but the basic detection principle is the same.

As described above, the inventors of the present application set a detection region Rd for detecting the touch position on the insulating substrate 2, and provide a signal input layer 41 for giving a measurement signal to the back surface side of the detection region Rd. A pattern of a conductive sheet 1 uniformly formed and formed with a detection layer 31 having a signal output node No. for outputting a measurement signal propagated via the substrate 2 on the surface side of the detection region Rd. We found that it is possible to detect the touch position with high accuracy by using it for a less touch panel. Specifically, since the signal input layer 41 and the detection layer 31 are separated, it is possible to prevent signal interference between the signal input node Ni and the signal output node No.

<Other embodiments>
In the above embodiment, the detection region Rd is rectangular, and the detection layer 31 and the signal input layer 41 are rectangular, but the present invention is not limited to this. For example, as shown in FIG. 12, the detection region Rd (detection layer 31 and signal input layer 41) may have an elliptical shape. The detection layer 31 is preferably formed in a region slightly wider than the signal input layer 41, as in the case of FIG. 1. Even if the detection region Rd has an elliptical shape, the principle of detecting the touch position is the same as that of the above embodiment, and detailed description thereof will be omitted here.

In the above embodiment, an example in which the wiring region Rw surrounds (surrounds) the detection layer 31 is shown, but the wiring region Rw is not limited to this, and the wiring region Rw is provided around the detection region Rd. It suffices if it is done. For example, when the substrate 2 is a rectangular film and the detection region Rd is also rectangular, the wiring region Rw is (1) U-shaped (provided around three sides of the detection region Rd). , (2) D-shaped (provided around two opposite sides of the detection area Rd) and (3) L-shaped (provided around two orthogonal sides of the detection area Rd). May be good. However, since the detection accuracy of the touch position can be improved by providing the electrodes E on each of the four sides of the detection layer 31, it is most preferable that the wiring region Rw surrounds the detection region Rd. Therefore, when the detection layer 31 of the detection region Rd has a rectangular shape, it is most preferable that the wiring region Rw is formed in a square shape.

Further, in the above embodiment, an example in which three electrodes 4 are provided at intermediate positions of each side of the detection layer 31 is shown, but the present invention is not limited to this. For example, electrodes E may be formed at the four corners of the detection layer 31 in addition to or instead of the intermediate positions of each side of the detection layer 31. Further, it is sufficient that at least two electrodes E are formed on the peripheral edge of the detection layer 31, and there is no particular limitation on which side and how many electrodes E are provided. For example, among the sides of the detection layer 31, there may be a side on which the electrode E is not provided. The arrangement of these electrodes E and the number of electrodes can be appropriately changed based on the design specifications such as the size of the patternless touch panel and the detection accuracy. However, the patternless touch panel has a feature that it is not necessary to provide a large number of electrodes as compared with the conventional (array type) touch panel. Specifically, the number of electrodes required for the patternless touch panel depends on the size of the panel and the required accuracy, but when the circumference of the detection layer 31 is less than 1 m, a total of 20 electrodes are formed on the peripheral edge of the detection layer 31. Sufficient detection accuracy can be obtained if (for example, 5 on each side) is used. When the size of the panel becomes large, the required number of electrodes may be appropriately increased according to the size. For example, even in a touch panel having a circumference of several meters of the detection layer 31 (for example, a whiteboard installed in a conference room or a classroom), a total of about 30 to 40 electrodes are provided on the peripheral edge of the detection layer 31. If there is, sufficient detection accuracy can be obtained.

Next, a specific embodiment will be described. It should be noted that the various numerical values described in the following examples are exemplified for the purpose of assisting the understanding of the invention, and are not intended to be limited to the numerical values described below at all.

(Example 1)
A PEN film (25 cm × 30 cm, thickness 50 μm) was bonded to the surface of a 25 cm × 30 cm, 1.6 mm thick FR4 substrate by optical adhesive (thickness 50 μm) to form the substrate 2.

-Coating the detection layer (conductive layer)-
The carbon-containing coating liquid has a carbon content of 2.5% by mass, a polyester resin of 12.0% by mass, and a balance solvent so as to be EXP28004EC black conch manufactured by Osaka Printing Ink Mfg. Co., Ltd. (carbon content 2. 5% by mass, polyester resin 12.0% by mass, balance solvent) was used. This coating liquid was applied to the detection region Rd on the surface of the PEN film of the substrate 2 by using direct gravure. Specifically, the coating range is a rectangular shape of 17 cm × 22 cm so that only the central portion of the PEN film, that is, the periphery of the detection layer is the wiring region Rw (margin where the conductive layer is not formed). .. Then, it dried at 120 degreeC for 1 minute. The detection layer 31 formed after drying had a carbon concentration of 17.2% by mass and a thickness of 2.64 μm.

-Formation of wiring-
Next, a plurality of output wirings 53 extending along the peripheral edge of the detection layer 31 were formed in the wiring region Rw on the surface of the PEN film of the substrate. It was formed by screen printing using Ag paste (DW-420L-2 manufactured by Toyobo Co., Ltd.) so that the line width of the output wiring 53 was 300 μm. In each output wiring 53, the distance between adjacent wirings is set to 200 μm. Further, the output wiring 53 adjacent to the side of the detection layer 31 has a distance D1 from the peripheral edge of the detection layer of 500 μm.

-Formation of the ground layer-
On the surface side of the detection layer 31, a ground layer 33 was formed in the detection region Rd via an insulating film as the insulating layer 32. The formation range of the ground layer 33 is set to be slightly narrower than that of the detection layer 31.

-Formation of signal input layer-
A signal input layer 41 set to be slightly narrower than the detection layer 31 was formed in the detection region Rd on the back surface of the substrate 2.

-Formation of insulating cover layer-
The entire front surface of the ground layer 33 and the entire back surface of the signal input layer 41 were covered with the insulating cover layers 34 and 43. A PEN film was attached to the surface of the ground layer 33 via an OCA film. Further, a solder resist was applied to the back surface of the signal input layer 41.

-Touch position detection test-
A conductive sheet 1 was installed on a prototype of a patternless touch panel (manufactured by Meisei University), and the accuracy of touch position detection by touch operation was verified. In the prototype, the conductive sheet 1 was placed statically on the acrylic plate with the detection layer 31 facing upward. Further, the output wiring 53 provided on the conductive sheet 1 was connected to the position detection unit 6. The position detection unit 6 acquires differential information such as the differential peak voltage based on the output signal output from the pair electrode arbitrarily selected, and the calculation unit 66 performs the calculation. The calculation unit 66 is set (programming) so that the differential information can be confirmed on the display screen (not shown).

As described above, a touch position detection test was performed on the prototype of the set patternless touch panel. Specifically, as shown in FIG. 9, the detection area of the conductive sheet is divided into 80 divided areas, and the experimenter touches the two points indicated by the circles or triangles with his / her finger and follows the arrow from there. I checked the output result when I moved my finger. In FIG. 9, for convenience of explanation, the electrodes provided on the left side / right side of the detection layer 31 are designated as E11 / E31, E12 / E32, and E13 / E33 in order from the top to the bottom of the drawing. Similarly, the electrodes provided on the upper / lower sides of the detection layer 31 are set to E21 / E41, E22 / E42, and E23 / E43 in order from the right to the left in the drawing.

The experimental results are shown in FIGS. 10 and 11. As shown in FIGS. 10 and 11, it was possible to detect a linear and large (significant) voltage change with the movement of the touch position in both the two-point touches of the circle and the triangle. By applying a deep learning algorithm using the concept of persetopron to this detection data, for example, the touch position can be calculated with good detection accuracy.

The learning data used for deep learning can be acquired by, for example, the following method. First, the net data in which the person and the environment are changed for the specific points appropriately thinned out for the divided area is acquired, and the specific points are learned. At this time, the net data may be acquired several hundred times or more, preferably 1,000 times or more. Then, the thinned out portion is interpolated by interpolation and extrapolation.

The present invention is extremely useful because it can provide a conductive sheet for a patternless touch panel having high touch position detection accuracy.

1 Conductive sheet (Conductive sheet for patternless touch panel)
2 Hypokeimenon 31 Detection layer 33 Ground layer (conducting layer on the surface side)
41 Signal input layer 6 Position detection unit Ni Signal input node No Signal output node Rd Detection area

Claims (8)

An insulating sheet-like substrate, a conductive signal input layer uniformly formed in a detection region including a central portion on the back surface side of the substrate, and a first signal input node provided on a peripheral portion thereof, and the above-mentioned conductive signal input layer. A conductive sheet having a conductive detection layer uniformly formed in the detection region on the surface side of the substrate and provided with a plurality of signal output nodes so as to be separated from each other at the peripheral edge portion.
A measurement signal is given to the first signal input node, and the position of an object close to the detection layer is based on the difference information of the output signals output from the paired node selected from the plurality of signal output nodes. A patternless touch panel characterized by having a position detection unit that calculates. The patternless touch panel according to claim 1, wherein a surface-side conductive layer is uniformly formed by laminating in the detection region on the surface side of the detection layer via an insulating layer. The patternless touch panel according to claim 2, wherein a second signal input node for receiving the measurement signal is provided on the surface-side conductive layer. On the surface of the substrate, a wiring region in which an output wiring connected to the signal output node is formed is provided around the detection layer.
The first signal input node is characterized in that an input wiring formed on the back surface of the substrate is connected to the region that overlaps with the wiring region in a plan view and does not overlap with the output wiring. The patternless touch panel described in 1. The patternless touch panel according to claim 2, wherein the thickness of the substrate is thicker than the thickness of the insulating layer. The detection layer is uniformly formed in a rectangular detection region, and is formed.
The patternless touch panel according to claim 1, wherein the signal output nodes are provided at least two locations on each side of the detection region so as to be separated from each other. The detection layer includes carbon, silver, copper, aluminum, indium tin oxide (ITO), fluorine-doped tin oxide (FTO), metal-doped zinc oxide, metal nanowire, antimonated tin oxide (ATO), polythiophene (PEDOT), and polyaniline. , And one or more selected from the group consisting of water-soluble sulfonated polyaniline.
The first aspect of the present invention, wherein the signal input layer contains one or more selected from the group consisting of copper, aluminum, and iron, and has a resistivity of 1 × 10-4 Ω · cm or less. Patternless touch panel. The substrate is alumina, glass cloth impregnated epoxy resin, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), cycloolefin polymer (COP), polycarbonate (PC), polyimide (PI), polyvinyl chloride (PVC), and Contains one or more selected from the group consisting of triacetate and triacetylcellulose (TAC).
The patternless touch panel according to claim 1, wherein the thickness of the substrate is 0.8 mm or more and 6.8 mm or less.

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