JP2019159447A - Patternless touch panel - Google Patents

Abstract

To provide a patternless touch panel which can realize position detection with high accuracy.SOLUTION: A patternless touch panel comprises a conductive sheet 1 and a position detection unit 6. The conductive sheet 1 includes an insulative sheet-like substrate 2, a conductive signal input layer 41 uniformly formed on a detection area Rd including a center portion on the back surface of the substrate 2, and a conductive detection layer 31 uniformly formed on the detection area Rd on the back surface of the substrate 2. The position detection unit 6 applies a measurement signal to a first signal input node Ni provided on the signal input layer 41 and calculates a position of an object approaching the detection layer 31 on the basis of difference information of an output signal output from a pair of electrodes E of the detection layer 31.SELECTED DRAWING: Figure 8

Description

  The present invention relates to a patternless touch panel, and more particularly, to a patternless touch panel provided with a conductive sheet suitably used for a 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 four corner electrodes of the conductive film, and the coordinate position is calculated based on the output voltage of the detection circuit. In Patent Document 2, pulse signals having the same phase and voltage are applied to the four corner electrodes of the rectangular conductive film, and the touch position of the user is detected using the log signal ratio. Further, in Patent Document 3, the resolution is increased by using a calculation method using nonlinear data. In these touch panels, there is no need 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 WO2013 / 153609 pamphlet JP 2013-250642 A JP, 2015-201223, A

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

  Accordingly, 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, there is provided 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 substrate surface. Using. Then, the signal detection unit gives a measurement signal to the first signal input node provided in the signal input layer, and the object approaches the detection layer based on the difference information of the output signal output from the pair node provided in the detection layer The position of was calculated.

  That is, the patternless touch panel according to one aspect of the present invention is formed uniformly in a detection region including an insulating sheet-like base and a central portion on the back side of the base and has a first signal input at a peripheral portion. A conductive signal input layer provided with nodes and a plurality of signal output nodes formed uniformly in the detection region on the surface side of the substrate and spaced apart from each other at the periphery. A conductive sheet having a sensing layer; and a measurement signal applied to the first signal input node, based on difference information of output signals output from a pair of nodes selected from the plurality of signal output nodes. A position detection unit for calculating the position of an object approaching the detection layer is provided.

  Here, the “sheet” includes, in addition to a sheet formed in a thin plate shape, a sheet formed in a film shape thinner than the thin plate. The same applies to the “sheet form”, which is a concept including a thin plate form and a film form.

  In the patternless touch panel described above, the inventors of the present invention are provided with a signal input layer in which a signal input node for inputting a measurement signal is provided on the surface of an insulating substrate, and a signal output node that is separated from the back surface of the substrate. It has been found that a conductive sheet in which the detection layers are uniformly formed is used for a patternless touch panel to have good detection accuracy. 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. it can.

  In the patternless touch panel according to the aspect described above, the surface-side conductive layer may be uniformly formed by lamination on the detection region on the surface of the detection layer via an insulating layer. Furthermore, a second signal input node that receives the measurement signal may be provided in the surface-side conductive layer.

  Thereby, a patternless touch panel having good detection accuracy can be realized even in a noisy environment.

  In the patternless touch panel according to the above aspect, a wiring region in which an output wiring connected to the signal output node is formed around the detection layer is provided on the base surface, and the first signal input node includes: An input wiring formed on the back surface of the substrate may be connected so as to overlap the wiring region in a plan view and not to overlap the output wiring.

  Thereby, it is possible to avoid the generation of 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 base may be thicker than the insulating layer.

  Thereby, the change of the electric potential concerning touch operation can be raised, and the detection accuracy of a touch position can be raised.

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

  Thereby, it is possible to obtain a patternless touch panel with good touch position detection accuracy and good temporal stability.

  As described above, according to the present invention, a patternless touch panel having high position detection accuracy can be obtained.

It is a top view which shows typically the conductive sheet for patternless touch panels which concerns on embodiment. It is a schematic sectional drawing in the II-II line of FIG. It is a top view which shows typically a ground layer and 2nd input wiring. It is a top view which shows a detection layer and output wiring typically. It is a top view which shows a signal input layer and 1st input wiring typically. It is a figure for demonstrating the position detection principle of the touchscreen to which a conductive sheet is applied. It is the figure which showed an example of the signal waveform when the point TP of FIG. 6 is touched. It is a figure which shows schematic structure of a patternless touch panel. It is a top view which shows the division area which divided | segmented the detection area of the electrically conductive sheet. It is a figure which shows the relationship between the touch position of two-point touch, and a peak voltage. It is a figure which shows the relationship between the touch position of 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 the preferred embodiments is merely exemplary in nature and is in no way intended to limit the invention, its application, or its application.

  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 approaching the detection layer 31 of the conductive sheet 1.

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

  The conductive sheet 1 is disposed 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 disposed before or after the display device.

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

  On the surface of the base 2, a detection layer 31, an insulating layer 32, and a ground layer 33 as a surface-side conductive layer are uniformly arranged in order from the side close to the base 2 in a rectangular detection region Rd including the central portion thereof. Formed and laminated. Similarly, the signal input layer 41 is uniformly formed on the back surface of the substrate 2 in the detection region Rd. The detection region Rd corresponds to a region for detecting a touch position when the conductive sheet 1 is used as a member of a patternless touch panel. In the present embodiment, it is assumed that the surface of the base 2 faces the operator. Also, “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.

-Substrate-
When the conductive sheet 1 is used as a member of the patternless touch panel, the base 2 is preferably made of an insulating material from the viewpoint of preventing a short circuit due to contact between the other member and the conductive layer 2. The base 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 is not particularly limited as long as it is an insulating material. For example, a hard plate “so-called FR4 (Flame Retardant Type 4) substrate” such as alumina or glass cloth-impregnated epoxy resin, which is made of resin. One or more materials selected from the group consisting of a film and a rubber material (preferably having flexibility) can be used. Among these, from the viewpoint of reducing the capacitance between the detection layer 31 and the signal input layer 41, an FR4 substrate having a low dielectric constant is desirable. Specific examples of the resin film include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), cycloolefin polymer (COP), polycarbonate (PC), polyimide (PI), polyvinyl chloride (PVC), triacetate, Examples thereof include triacetyl cellulose (TAC). Particularly, a PET film is more preferable from the viewpoints of heat resistance and cost. Since these films contain a plasticizer, they have some flexibility and can function 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. To the position detection unit 6 and the like. When 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, A sufficient output signal may not be obtained. Specifically, the thickness of the substrate is preferably 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 the substrate 2 from the viewpoint of avoiding bonding stress, for example, 10 μm to 200 μm.

  Moreover, when arrange | positioning the electrically conductive sheet 1 in the front side of the above-mentioned display device, from the viewpoint of ensuring visibility, the base | substrate 2 has a high thing (for example, transparent) with a high light transmittance. On the other hand, when the conductive sheet 1 is disposed on the rear side of the display device, the substrate 2 does not need to be highly transmissive (for example, 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 a touch position when the conductive sheet 1 is used as a member of a patternless touch panel. In other words, the conductive sheet 1 of the present invention is configured such that the presence or absence of a touch operation can be detected by the position detection unit 6 (see FIG. 8) by being mounted on a patternless touch panel. The detection layer 31 is uniform in a detection layer formation region R1 slightly wider than the detection region Rd from the viewpoint of avoiding the generation of capacitance between the electrode E and the output wiring 53 and the signal input layer 41 and the ground layer 33. It is desirable that it is formed. 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 portion), a plurality of electrodes E (corresponding to signal output nodes No.) are arranged at equal pitches at intermediate positions in the longitudinal direction of the sides spaced from the corners of the respective sides. Is formed. The number of electrodes E is equal to the number of output wirings 53 in the wiring area described later. FIG. 1 shows an example in which three electrodes E are provided on each side of the conductive layer 22. In the present embodiment, “equal” only needs to be substantially equal, and the same effect can be obtained even if there is a slight misalignment. Therefore, “equal” is a concept including substantially equal in addition to being equal (completely matching).

  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 “touch operation” is referred to as “touching”. A position on the conductive layer 2 corresponding to the position of the indicator (for example, the operator's finger) when the “touch operation” is performed is referred to as a “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, antimony-doped tin oxide (ATO), polythiophene (PEDOT), One or more conductive materials selected from the group consisting of polyaniline and water-soluble sulfonated polyaniline are contained. The carbon is not particularly limited as long as it exhibits electrical conductivity. For example, carbon black, graphene, or carbon nanotube 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. From the viewpoint of workability, 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 from the viewpoint of stability over time, a polyester resin, acrylic resin, polyurethane ester resin, and epoxy resin that are resistant to moisture and heat are desirable. Specifically, water solubility of polyester resin, fluorine rubber, diene rubber, styrene rubber, nitrile rubber, acrylic rubber, butyl rubber, thiocol, fluorine resin, polyolefin resin, acrylic resin, nitrile resin, etc. is 1%. Less than resin can be used conveniently. Note that the conductive layer may contain a crosslinking agent.

(Detection layer resistance)
From the viewpoint of obtaining the conductive sheet 1 having excellent detection accuracy and excellent temporal stability, the detection layer 31 preferably has a resistance value of 1 kΩ / □ or more in small and medium-sized applications (for example, tablet PCs). . If the resistance value is less than 1 kΩ / □, the peak time generated by the differential potential of the detection current from the two electrodes becomes small, so that it is difficult to distinguish from noise when the touch position is detected by the position detection unit 6. There is a risk that. On the other hand, in a large application (for example, a large panel), since the resistance from the touch position to the electrode E of the detection layer 31 is high, a lower limit resistance value of 50Ω / □ or more is sufficient. In both small and medium-sized applications, the resistance value of the detection layer 31 is preferably 10 MΩ / □ or less. When the resistance value exceeds 10 MΩ / □, in the detection of the touch position by the position detection unit 6, not only the sensitivity is lowered due to the decrease in the output due to the resistance, but also there is a possibility that a delay occurs.

(Detection layer resistance variation)
The variation in the resistance value of the detection layer 31 is preferably 20% or less from the viewpoint of obtaining stability in detection accuracy. By suppressing the resistance value variation 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.

(Detection layer thickness)
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 a patternless touch panel. It is as follows.

  Note that the thickness of the detection layer 31 is desirably 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. When the thickness of the detection layer 31 is uniform, variation in the resistance value of the detection layer 31 is reduced, and stable detection accuracy can be obtained and stability over time can be improved.

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

  On the other hand, when the conductive sheet 1 is disposed 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 with low transparency. is there. Specifically, the total light transmittance of the conductive sheet 1 is 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 periphery of the detection layer 31 are formed in the wiring region Rw on the substrate surface. 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, the respective output wirings 53 are connected to the detection layer 31 via the electrodes E provided so as to be separated from each other, and the electrodes E function as signal output nodes. Each output wiring 53 is routed along the periphery of the detection layer 31, concentrated at one place (in the vicinity of the lower right corner in FIG. 1), and connected to different electrodes E. In this way, by consolidating the ends (electrodes) of the output wiring 53, it becomes easy to connect to the position detection unit 6.

  The material of the output wiring 53 is not particularly limited, and known metal wires such as gold, silver, copper, and aluminum, metal foil, and conductive paste can be used. From the viewpoint of adhesion between the output wiring 53 and the detection layer 31 via the electrode E, 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, and mixed powders, and the shape is not particularly limited. For example, it may be spherical or flake shaped.

(Resistance value of output wiring)
The output wiring 53 preferably has a resistivity of 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, a voltage drop due to the output wiring 53 becomes large, and an unnecessarily high voltage is applied to the signal input node Ni (second and third electrodes E2 and E3) described later. May have to be applied.

(Output wiring size and spacing with 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, 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 disconnected or the resistance value of the wiring region Rw is increased. Further, when the line width of the output wiring 53 exceeds 1000 μm, there is a possibility that the capacity of the wiring region Rw not involved in the detection of the touch position may be increased.

  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, the wiring may be disconnected or the resistance value may increase due to handling. On the other hand, if the thickness of the output wiring 53 exceeds 20 μm, the workability may be remarkably lowered due to an increase in viscosity, the necessity of twice coating, or the like.

  Further, the output wiring 53 may be wired away from the detection layer 31 and other output wirings 53 except for the connection portion (electrode E) to 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. Thereby, noise can be prevented from being superimposed on the output wiring 53.

-Grounding layer (surface-side conductive layer)-
As shown in FIG. 2, a conductive ground layer 33 is uniformly formed on the surface side of the detection layer 31 and the output wiring 53 with an insulating layer 32 interposed therebetween.

  The insulating layer 32 can be comprised with the insulating film affixed with the adhesive film, for example. In addition, since the material and thickness of the insulating film which comprises the insulating layer 32 can be set with the same view as the insulating film which comprises the base | substrate 2, the detailed description is abbreviate | omitted here.

  As shown in FIG. 3, the ground layer 33 is uniformly formed in the ground layer formation region R <b> 2 having substantially the same area as the detection region Rd. That is, the formation range of the ground layer 33 is formed so as to be slightly narrower than the detection layer 31 and not to overlap the electrode E of the detection layer 31 in plan view. Thereby, it is possible to avoid the generation of a capacitance 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 indicated by solid lines, and the detection layer 31 is indicated by broken lines.

The ground layer 33 preferably has a low resistivity. For example, the resistivity is preferably 1 × 10 ⁻⁴ Ω · cm or less. The ground layer 33 is preferably a metallic conductor containing one or more selected from the group consisting of copper, aluminum, and iron. For example, copper, aluminum, iron, or an alloy thereof. In the case where the second input wiring 52 is soldered to the ground layer 33, it is preferable to employ copper as the ground layer 33.

  A signal input node Ni is provided at an intermediate position on the upper side (corresponding to the peripheral portion) of the ground layer 33 on the left side in the horizontal direction of the drawing. A second input wiring 52 that is wider than the output wiring 53 is connected to the signal input node Ni. 3, the second input wiring 52 extends in an L shape along the periphery of the base 2 to the middle of the right side in the vertical direction toward the right and down in the drawing. . A pattern generator PG of the position detector 6 described later is connected to the tip of the second input wiring 52. Then, a 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 similarly to the output wiring 53, and detailed description thereof is 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 base 2. As shown in FIGS. 4 and 5, the signal input layer 41 is uniformly formed in the signal input layer formation region R <b> 3 having substantially the same area as the detection region Rd. The ground layer 33 and the signal input layer 41 are arranged so that their positions in the plan view in the conductive sheet 1 are substantially the same. In FIG. 4, the detection layer 31 and the output wiring 53 are indicated by solid lines, and the signal input layer 41 and the first input wiring 51 are indicated by broken lines. In FIG. 5, the signal input layer 41 and the first input wiring 51 are indicated by solid lines, and the detection layer 31 is indicated by broken lines.

  As shown in FIG. 5, a signal input node Ni is provided at an intermediate position on the upper left side (corresponding to a peripheral portion) of the signal input layer 41 in the left-right direction in the drawing. A first input wiring 51 that is wider than the output wiring 53 is connected to the signal input node Ni. The 1st input wiring 51 and the 2nd input wiring 52 are arrange | positioned so that the mutual position in the planar view in the conductive sheet 1 may become substantially the same. Specifically, the first input wiring 51 extends in the upper direction of the drawing in FIG. 5, and then extends in an L shape along the periphery of the conductive sheet toward the right side and the lower side of the drawing. Extends to an intermediate position. A pattern generator PG of the position detector 6 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 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. For example, the resistivity is preferably 1 × 10 ⁻⁴ Ω · cm or less. 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 an alloy thereof.

  Further, as shown in FIGS. 2 and 4, the ground wiring 42 is formed on the back surface of the base 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. Thus, by providing the ground wiring 42 on the back side of the output wiring 53, 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 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). Since the insulating film 34 can be the same as the insulating film 22 constituting the substrate 2, its detailed description is omitted here.

  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 before or after the conductive sheet 1, insulating parts are disposed, or the conductive sheet 1 is covered with a housing or the like, the insulating cover layer is not provided. May be.

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

  The analog switches 61 and 61 allow 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 to pass therethrough. The differential amplifier 62 outputs a differential signal indicating a signal amount difference between 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 / digital conversion circuit 65 converts the peak voltage value and the sign information of the peak voltage into a digital value 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 the pair electrodes E1 and E2 (corresponding to the pair node) from the electrodes E provided on the detection layer 31, and outputs the electrode selection signal SC1 indicating the pair electrodes E1 and E2 to the two analog switches 61. , 61. Furthermore, the calculation unit 66 determines the position of an object (for example, a user's finger) that has approached or contacted the detection layer 31 based on the difference information included in the differential signal (digital value) output from the analog-digital conversion circuit 65. Is obtained by calculation. Here, the difference information refers to all information obtained based on the differential signal. For example, the difference information includes sign 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. Time information etc. are included. In addition, the calculation unit 66 includes a storage unit (not shown) that stores a ROM that stores a program for performing the above control.

<Touch panel position detection principle>
Hereinafter, the detection principle of 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 diagram showing a state in which the pulse generator PG and the differential amplifier 62 of the position detection unit 6 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. The impedance Z is matched to a predetermined value (for example, about 50Ω). 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 through the input resistor Ria. 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.

  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 base 21 and is output as an output signal from the electrode E of the detection layer 31. The differential amplifier 62 is supplied with output signals output from the pair electrodes E1 and E2 via the analog switches 61 and 61. Thereafter, the touch position is calculated by the calculation unit 66 (see FIG. 8) connected to the subsequent stage.

  Specifically, when a pulse signal is supplied to the signal input node Ni in a state where the touch position TP is touched, the touch position is charged up, and the pair electrodes E1 and E2 are respectively in accordance with the following formula (1). Output voltage.

  V = Vdd (1-exp (−t / RC)) (1)

C = C _T + C _S (2)

Here, Formula (2) has shown the value of C of Formula (1). In the formula (2), C _T is the capacitance between the sensing layer 31 and the touched finger, C _S is the internal volume of the conductive sheet 1 at the touch position TP. Note that Cs is preferably set so that the value of Ct / Cs is about 1 to 100.

Further, R in the expression (1) includes R ₁ and R ₂ which are resistance values between the electrodes E1 and E2 constituting the pair electrode and the touch position, and each of the electrodes E1 and E2 to the position detection device 6. The wiring resistance R _L 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 R _L and the resistance component R _Z can be reduced to the extent little effect, the following calculation, the wiring resistance R _L and the resistance component R _Z is assumed to be "0" (zero).

Then, when the resistance between the one electrode E1 and the touch position TP of the pair electrodes and R _1, the electrode E1, the voltage indicated by the following formula (3), respectively, are outputted.

V ₁ = Vdd (1-exp (−t / R ₁ C)) (3)

Similarly, when the resistance between the other electrode E2 and the touch position TP of the pair electrodes and R _2, the electrode E2, the voltage indicated by the following formula (4), respectively, are outputted.

V ₂ = Vdd (1-exp (−t / R ₂ C)) (4)

  Accordingly, the differential amplifier 42 outputs a differential signal (difference signal between the expressions (3) and (4)) shown in the following expression (5).

Vdf = V ₁ −V _{2
= Vdd (-exp (-t / R} 1 C) + exp (-t / R 2 C)) ‥ (5)

FIG. 7 is a diagram illustrating an example of the output signals of the pair electrodes E1 and E2 and the differential signal output from the differential amplifier 42 when the touch position TP is touched by the user. In FIG. 7, the vertical axis represents voltage values, and the horizontal axis represents time. FIG. 7A shows signal waveforms of V ₁ and V ₂ obtained by equations (1) and (2) described later, and FIG. 7B shows the V _df obtained by equation (3). The signal waveform is shown.

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

  Note that 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 independent of the type of touch operation. The same. Similarly, when the touch position is one point (so-called one-point touch), when the touch position is two points (so-called two-point touch), and when the touch position is three points or more (so-called multi-touch), position detection is performed. Although the amplitude of the voltage detected by the unit 6 is different, the basic detection principle is the same.

  As described above, the inventors of the present application set the detection region Rd for detecting the touch position on the insulating base 2, and the signal input layer 41 for supplying the measurement signal to the back side of the detection region Rd. The conductive sheet 1 in which the detection layer 31 is formed in which the signal output node No for outputting the measurement signal propagated through the base 2 is formed uniformly is formed on the surface side of the detection region Rd. It was found that the touch position can be detected with high precision by using it for a touchless 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. However, the present invention is not limited to this. For example, as shown in FIG. 12, the detection region Rd (the detection layer 31 and the signal input layer 41) may be elliptical. The detection layer 31 is preferably formed in an area slightly wider than the signal input layer 41, as in the case of FIG. Note that even if the detection region Rd has an elliptical shape, the detection principle of the touch position is the same as in the above embodiment, and a detailed description thereof is omitted here.

  In the above embodiment, an example is shown in which the wiring region Rw surrounds (encloses) the detection layer 31. However, the present invention is not limited to this, and the wiring region Rw is provided around the detection region Rd. It only has to be 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 the three sides of the detection region Rd). (2) D-shape (provided around two opposing sides of the detection region Rd) and (3) L-shape (provided around two orthogonal sides of the detection region Rd) Also 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 in the detection region Rd is rectangular, the wiring region Rw is most preferably formed in a square shape.

  Moreover, although the example which provided each three electrode 4 in the intermediate position of each edge | side of the detection layer 31 was shown in the said embodiment, it is not limited to this. For example, the electrodes E may be formed at the four corners of the detection layer 31 in addition to or instead of the intermediate position of each side of the detection layer 31. Further, it is only necessary that at least two electrodes E in total are formed on the peripheral portion of the detection layer 31, and there is no particular limitation on how many electrodes E are provided on which side. For example, there may be a side where the electrode E is not provided among the sides of the detection layer 31. The arrangement of the electrodes E and the number of electrodes can be appropriately changed based on design specifications such as the size and detection accuracy of the patternless touch panel. However, the patternless touch panel has a feature that it is not necessary to provide a large number of electrodes, as compared with a 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 on the periphery of the detection layer 31 Sufficient detection accuracy can be obtained with (for example, five on each side). The required number of electrodes may be increased as appropriate in accordance with the size of the panel when the size of the panel is increased. For example, even in a touch panel (for example, a white board installed in a conference room or a classroom) where the circumference of the detection layer 31 is several meters, a total of about 30 to 40 electrodes are provided on the periphery of the detection layer 31. If there is, sufficient detection accuracy can be obtained.

  Next, specific examples will be described. The various numerical values described in the following examples are given for the purpose of assisting understanding of the invention, and are not intended to be limited to the numerical values described below.

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

-Coating of detection layer (conductive layer)-
The coating liquid containing carbon is EXP28004EC black concrete (carbon content 2. 5% by mass, polyester resin 12.0% by mass, remaining solvent). This coating solution was applied to the detection region Rd on the surface of the PEN film of the substrate 2 using a direct gravure. Specifically, the application range was a rectangular area of 17 cm × 22 cm so that only the central portion of the PEN film, that is, the periphery of the detection layer was the wiring region Rw (a blank where no conductive layer was 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.

-Wiring formation-
Next, a plurality of output wirings 53 extending along the periphery of the detection layer 31 were formed in the wiring region Rw on the surface of the PEN film of the base. The output wiring 53 was formed using Ag paste (DW-420L-2 manufactured by Toyobo Co., Ltd.) by screen printing so that the line width of the output wiring 53 was 300 μm. Each output wiring 53 was set such that the distance between adjacent wirings was 200 μm. Further, the output wiring 53 adjacent to the side of the detection layer 31 is set to have a distance D1 of 500 μm from the periphery of the detection layer.

-Formation of ground layer-
On the surface side of the detection layer 31, the 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 so as 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 insulation cover layer-
The entire surface of the ground layer 33 and the entire back surface of the signal input layer 41 were covered with insulating cover layers 34 and 43. A PEN film was attached to the surface of the ground layer 33 via an OCA film. A solder resist was applied to the back surface of the signal input layer 41.

-Touch position detection test-
The conductive sheet 1 was installed in a prototype of a patternless touch panel (Myosei University), and the detection accuracy of the touch position by the touch operation was verified. In the prototype, the conductive sheet 1 was left 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 a differential peak voltage based on an output signal output from an arbitrarily selected pair electrode, and the calculation unit 66 performs calculation. The calculation unit 66 is set (programmed) so that differential information can be confirmed on a display screen (not shown).

  As described above, the 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 two points indicated by circles or triangles with a finger, and then follows the arrows. Check the output results when moving your finger. In FIG. 9, for convenience of explanation, among the electrodes E, the electrodes provided on the left side / right side of the detection layer 31 are 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 side / lower side of the detection layer 31 were designated as E21 / E41, E22 / E42, E23 / E43 in order from the right to the left in the drawing.

  The experimental results are shown in FIGS. As shown in FIGS. 10 and 11, in both the two-point touches of the circle mark and the triangle mark, a linear and large (significant) voltage change can be detected with the movement of the touch position. For example, by applying a deep learning algorithm using the concept of percepron to the detection data, the touch position can be calculated with good detection accuracy.

  The learning data used for deep learning can be acquired by the following method, for example. First, net data obtained by changing the person or the environment with respect to a specific point appropriately thinned out from the divided area is acquired, and the specific point is learned. At this time, the acquisition of the net data may be performed several hundred times or more, preferably 1000 times or more. Thereafter, the thinned 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 with high touch position detection accuracy.

1 Conductive sheet (Conductive sheet for patternless touch panel)
2 Substrate 31 Detection layer 33 Ground layer (surface-side conductive layer)
41 Signal Input Layer 6 Position Detection Unit Ni Signal Input Node No Signal Output Node Rd Detection Area

Claims (8)

A sheet-like substrate having insulating properties, a conductive signal input layer uniformly formed in a detection region including a central portion on the back side of the substrate, and provided with a first signal input node at a peripheral portion; A conductive sheet having a conductive detection layer formed uniformly in the detection region on the surface side of the substrate and provided with a plurality of signal output nodes so as to be spaced apart from each other at the peripheral edge;
A position of an object that has approached the detection layer based on difference information of an output signal that is output from a pair node selected from the plurality of signal output nodes by giving a measurement signal to the first signal input node A patternless touch panel, comprising: a position detection unit for calculating the position. The patternless touch panel according to claim 1, wherein a surface-side conductive layer is uniformly formed by lamination on 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. The substrate surface is provided with a wiring region in which an output wiring connected to the signal output node is formed around the detection layer,
The input wiring formed on the back surface of the base is connected to the first signal input node so as not to overlap the output wiring in a region overlapping the wiring region in plan view. 1. The patternless touch panel according to 1. The patternless touch panel according to claim 2, wherein a thickness of the base is thicker than a thickness of the insulating layer. The detection layer is uniformly formed in a rectangular detection region,
The patternless touch panel according to claim 1, wherein at least two signal output nodes are provided on each side of the detection area 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 nanowires, antimony-doped tin oxide (ATO), polythiophene (PEDOT), and polyaniline. And one or more selected from the group consisting of water-soluble sulfonated polyaniline,
The signal input layer contains at least one 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 includes alumina, glass cloth impregnated epoxy resin, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), cycloolefin polymer (COP), polycarbonate (PC), polyimide (PI), polyvinyl chloride (PVC), and Containing one or more selected from the group consisting of triacetate and triacetylcellulose (TAC),
The patternless touch panel according to claim 1, wherein a thickness of the substrate is 0.8 mm or more and 6.8 mm or less.

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