JP2015130061A - touch panel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain a touch panel with a pressure sensitive function that can maintain the excellent pressure sensitive function over a long period of time.SOLUTION: The present invention relates to a touch panel 5, and the touch panel 5 comprises: a plurality of first electrodes 14 that is rowed in an X-axis direction; a plurality of second electrodes 24 that is rowed in a Y-axis direction; and a composition that includes a plurality of conductivity particles 33 different in particle diameters distributed in a binder 32. The touch panel includes: a pressure sensitive layer 30 that covers the first electrode 14; and a protection layer 40 that has a thickness smaller than an average particle-to-particle distance expressing an average value of spaced distances between mutually adjacent conductivity particles 33, and is provided between the pressure sensitive layer 30 and the second electrode 24.

Description

  The present invention relates to a touch panel (a touch panel with a pressure sensitive function) that can detect a pressing force in addition to a pressing position when a user touches with a finger or a stylus.

  As such a touch panel, a device described in International Publication No. 2012/176624 (Patent Document 1) is known. The device of Patent Document 1 includes at least one of a plurality of upper transparent electrodes 11a arranged side by side in the X-axis direction, a plurality of lower transparent electrodes 12a arranged side by side in the Y-axis direction, and the transparent electrodes 11a and 12a. And a transparent pressure-sensitive ink member 13 for covering (see FIGS. 2, 4, 5, etc. of Patent Document 1).

  In the apparatus of Patent Document 1, the transparent pressure-sensitive ink member 13 is made of a material whose resistance value changes in accordance with the applied external force. Therefore, the magnitude of the external force can be detected based on the resistance value change. it can. By utilizing this, the pressure-sensitive function is realized with the transparent pressure-sensitive ink member 13 as a core. And the touch panel with a pressure-sensitive function is implement | achieved in combination with the position detection function implement | achieved by making the several upper transparent electrode 11a and the several lower transparent electrode 12a into a core. Note that Patent Document 1 also describes that the transparent pressure-sensitive ink member 13 is made of a composition containing a plurality of conductive particles (see Paragraph 0039 of Patent Document 1).

  In general, the plurality of conductive particles contained in the composition exhibit a predetermined particle size distribution, and the particle size varies. For this reason, the pressure-sensitive layer (transparent pressure-sensitive ink member 13) may contain conductive particles having a particle size larger than the set thickness. In such a case, some conductive particles are exposed from the surface of the pressure sensitive layer. When the touch panel is repeatedly used in this state, the electrode (upper transparent electrode 11a) facing the pressure-sensitive layer may be rubbed with the exposed conductive particles and damaged. In addition, the conductive particles themselves may be damaged or peeled off from the pressure-sensitive layer. When the electrode or the conductive particles are damaged or the conductive particles are peeled off, the resistance value increases, and as a result, the pressure-sensitive function may be lowered.

International Publication No. 2012/176624

  Therefore, it is desired to realize a touch panel with a pressure sensitive function capable of maintaining a good pressure sensitive function over a long period of time.

The characteristic configuration of the touch panel according to the present invention is as follows.
A plurality of first electrodes arranged in parallel to each other so as to be aligned in a first direction;
A plurality of second electrodes opposed to the plurality of first electrodes and arranged in parallel to each other so as to be aligned in a second direction intersecting the first direction;
A pressure-sensitive layer comprising a plurality of conductive particles having different particle diameters dispersed in a binder, covering at least a plurality of the first electrodes, and having electrical characteristics that change according to external force;
A protective layer provided between the pressure-sensitive layer and the second electrode, having a thickness smaller than an average inter-particle distance representing an average value of a separation distance between the conductive particles adjacent to each other;
It is in the point provided with.

  In the present application, the “average interparticle distance” means the basic average interparticle distance as an average value of the distance between the conductive particles adjacent to each other in each of a plurality of sections that are virtually set dispersed in the pressure-sensitive layer. And the distance determined by calculating the average value (overall average value) of the basic average interparticle distance determined for each section.

  According to this characteristic configuration, the input position can be appropriately determined by the first electrode and the second electrode functioning centrally as in the conventional touch panel. Moreover, since the pressure-sensitive layer is made of a material whose electrical characteristics change according to an external force, the magnitude of the pressing force on the touch panel can be appropriately determined based on the change in the electrical characteristics. Therefore, a pressure-sensitive touch panel is realized.

  Moreover, according to said characteristic structure, since the protective layer is provided between the pressure sensitive layer and the 2nd electrode, when some electroconductive particle with a large particle size is exposed from the surface of a pressure sensitive layer Even so, it is possible to prevent the second electrode and the exposed conductive particles from rubbing against each other. Therefore, it can suppress effectively that a 2nd electrode and electroconductive particle are damaged, or that electroconductive particle peels from a pressure sensitive layer. Therefore, a touch panel with a pressure sensitive function capable of maintaining a good pressure sensitive function over a long period of time is realized.

  Furthermore, according to the above characteristic configuration, since the thickness of the protective layer is set smaller than the average interparticle distance, in the protective layer, it is difficult to energize in the first direction (and the second direction), and conversely the thickness direction The structure is easy to energize. For this reason, it is easy to ensure insulation between the adjacent first electrodes, and the position detection function is appropriately realized. Moreover, it is easy to ensure the energization between the 1st electrode and the 2nd electrode at the time of a press, and a pressure-sensitive function is implement | achieved appropriately. Therefore, the position detection function and the pressure-sensitive function are not impaired due to the provision of the additional protective layer. Therefore, both the position detection function and the pressure-sensitive function in the pressure-sensitive touch panel can be favorably maintained.

  Hereinafter, preferred embodiments of the present invention will be described. However, the scope of the present invention is not limited by the preferred embodiments described below.

  As one aspect, it is preferable that the thickness of the protective layer is set so as to energize in the thickness direction and not in the first direction.

  According to this structure, the insulation between adjacent 1st electrodes can be ensured appropriately. In addition, it is possible to appropriately ensure energization between the first electrode and the second electrode during pressing. Therefore, a good pressure sensitive function can be maintained over a long period of time while ensuring an appropriate function of the pressure sensitive touch panel.

  As one aspect, it is preferable that the thickness of the protective layer is set larger than the average particle diameter of the conductive particles.

  The exposed height of the conductive particles exposed from the surface of the pressure-sensitive layer is defined by the difference between the particle diameter of each conductive particle and the thickness of the binder layer. For this reason, by setting the thickness of the protective layer to be larger than the average particle diameter of the conductive particles as described above, the entire exposed portion of the many conductive particles can be covered with the protective layer. Moreover, also about other electroconductive particle, many of the exposed parts can be covered with a protective layer. Therefore, it can suppress more effectively that the 2nd electrode and conductive particles rub against each other. As a result, the pressure sensitive function can be maintained better.

  As one aspect, it is preferable that the protective layer is made of a material softer than the material constituting the conductive particles.

  According to this configuration, even if the second electrode and the protective layer are rubbed together, it is possible to suppress the second electrode from being damaged. Therefore, the pressure sensitive function can be maintained better.

  As one aspect, one pressure-sensitive layer is provided so as to cover only the plurality of first electrodes, and one protective layer is provided so as to be in contact with the pressure-sensitive layer. Is preferred.

  According to this configuration, it is possible to realize a touch panel with a pressure-sensitive function that has a simple and sufficient function by introducing only one pressure-sensitive layer and one protective layer. Further, in this configuration, since the protective layer is provided directly on the pressure-sensitive layer, the surface roughness of the pressure-sensitive layer due to the variation in the particle diameter of the conductive particles is improved. Therefore, the detection sensitivity of the pressing force can be stabilized, and as a result, the detection accuracy of the pressing force can be increased.

Perspective view of an electronic device equipped with a pressure-sensitive touch panel II-II sectional view in FIG. Exploded perspective view of touch panel Graph showing particle size distribution of conductive particles Partial enlarged view in FIG. Illustration of how to determine the average interparticle distance Graph showing comparison of FR characteristics before and after durability test Partial enlarged view showing another aspect of the touch panel Partial enlarged view showing another aspect of the touch panel Partial enlarged view showing another aspect of the touch panel

  An embodiment of a touch panel according to the present invention will be described with reference to the drawings. The touch panel 5 according to the present embodiment is provided in the electronic device 1 such as a mobile phone or a portable game machine, and functions as a touch input device. In the present embodiment, a capacitive touch panel 5 mounted on a multi-function mobile phone (smart phone) as a kind of the electronic device 1 will be described as an example. In the following description, a side on which an input surface (an operation surface 26a described later) of the touch panel 5 is located is referred to as a “front side”. This “front side” is also the side facing the user who operates the electronic device 1. On the contrary, the back side when viewed from the user operating the electronic device 1 is referred to as a “back side”.

  As shown in FIGS. 1 and 2, the electronic device 1 is arranged in a substantially rectangular parallelepiped casing 3, a display device 4 built in the casing 3, and the display device 4 so as to overlap the front side. Touch panel 5. The housing 3 is made of synthetic resin. The housing | casing 3 is provided with the recessed part 3a opened in a rectangular shape toward the front side. The concave portion 3a is formed to have a step, and this step portion functions as a support portion 3b that supports the touch panel 5 from the back side. The support portion 3b is formed in a rectangular frame shape (frame shape) corresponding to the shape of the recess 3a. The display device 4 is stored in a region (first storage recess) on the back side of the support portion 3b (stepped portion), and is supported by the support portion 3b in a region on the front side (second storage recess). The touch panel 5 is accommodated. The display device 4 is constituted by, for example, a liquid crystal display panel or an organic EL display panel.

  The shape and size of the recess 3a (first storage recess and second storage recess) can be appropriately set according to the shape and size of the display device 4 and the touch panel 5. In the present embodiment, as an example, both the display device 4 and the touch panel 5 have a substantially rectangular parallelepiped shape, and the dimensions in a plan view (viewed from the front side) of the touch panel 5 are larger than those of the display device 4. Is bigger. The recess 3a is in contact with the side surface of the first storage recess and the side surface of the display device 4, and is in contact with the side surface of the second storage recess and the side surface of the touch panel 5, and the surface of the display device 4 and the surface of the support portion 3b And the surface of the housing 3 and the surface of the touch panel 5 are formed to have substantially the same height.

  In the present embodiment, when the user touches the operation surface 26a with a finger or a stylus, the touch panel 5 simultaneously detects the magnitude of the pressing force on the operation surface 26a in addition to the pressing position on the operation surface 26a. It is configured as follows. That is, the touch panel 5 according to the present embodiment is configured as a pressure-sensitive touch panel.

  As shown in FIG. 3, the touch panel 5 includes a first electrode forming member 10, a second electrode forming member 20, and a pressure sensitive layer 30. The touch panel 5 according to the present embodiment further includes a protective layer 40. The 1st electrode formation member 10, the pressure sensitive layer 30, and the protective layer 40 are laminated | stacked in order of description toward the front side from the back side (refer FIG. 5). The pressure sensitive layer 30 is disposed on the first electrode forming member 10, and the protective layer 40 is disposed on the pressure sensitive layer 30. Further, the second electrode forming member 20 is disposed on the front side with respect to the protective layer 40 at a predetermined interval.

  Moreover, in this embodiment, the 1st electrode formation member 10 and the 2nd electrode formation member 20 are all formed in the rectangular shape, and are arrange | positioned so that it may overlap with planar view. Then, the direction along one side of the four sides forming the rectangular shape is defined as an “X-axis direction” in the present embodiment, and another side that intersects (is orthogonal to in this example) the one side. The direction along is defined as “Y-axis direction” in the present embodiment. In the present embodiment, an XY coordinate system (XY orthogonal coordinate system) is configured based on the X-axis direction and the Y-axis direction that are orthogonal to each other. In the present embodiment, the X-axis direction corresponds to the “first direction” in the present invention, and the Y-axis direction corresponds to the “second direction” in the present invention. Note that the XY coordinate system may be configured based on the X-axis direction and the Y-axis direction that intersect each other at non-right angles. In the present embodiment, a direction orthogonal to both the X-axis direction and the Y-axis direction is defined as a “Z-axis direction”. This Z-axis direction is also the stacking direction (thickness direction) of each member constituting the touch panel 5.

  As shown in FIG. 3, the first electrode forming member 10 includes a first substrate 12 and a plurality (eight in this example) of first electrodes 14 formed on the first substrate 12. The first substrate 12 is preferably configured using a material excellent in transparency, flexibility, insulation, and the like. Examples of materials that satisfy such requirements include general-purpose resins such as polyethylene terephthalate and acrylic resins, general-purpose engineering resins such as polyacetal resins and polycarbonate resins, and super engineering resins such as polysulfone resins and polyphenylene sulfide resins. Is exemplified. The thickness of the 1st board | substrate 12 can be 25 micrometers-100 micrometers, for example. In this embodiment, the 1st board | substrate 12 is comprised with the polyethylene terephthalate film.

  In the present embodiment, the first electrode 14 is formed on the surface of the first substrate 12 on the front side (second electrode forming member 20 side). The plurality of first electrodes 14 are arranged in parallel to each other so as to be arranged at a predetermined interval in the X-axis direction. In the present embodiment, the first electrode 14 is formed in a stripe shape (a linear shape having a certain width). Note that the first electrode 14 may be formed in, for example, a wave shape or a zigzag shape. In any case, each of the first electrodes 14 is formed so as to extend along the Y-axis direction as a whole.

  It is preferable that the 1st electrode 14 is comprised using the material excellent in transparency. Examples of materials that satisfy these requirements include metal oxides such as tin oxide, indium oxide, antimony oxide, zinc oxide, cadmium oxide, and ITO (Indium Tin Oxide), silver nanowires, carbon nanotubes, and conductive polymers. Etc. are exemplified. The 1st electrode 14 is a transparent conductive film comprised using these materials, The thickness can be 5 nm-5000 nm, for example. In the present embodiment, the first electrode 14 is composed of an ITO thin film.

  Examples of the method for forming the first electrode 14 include a method in which a transparent conductive film is formed on the entire surface of the first substrate 12 and then unnecessary portions are removed by etching. The entire surface of the transparent conductive film can be formed by, for example, a vacuum deposition method, a sputtering method, an ion plating method, a CVD method, a roll coater method, or the like. Etching can be performed by immersing the resist in an etching solution such as hydrochloric acid after forming a resist by a photolithography method, a screen printing method, or the like in a portion to be left as an electrode. Etching is carried out by removing the transparent conductive film where the resist is not formed by spraying an etching solution after the resist is formed, and then swelling or dissolving the resist by immersion in a solvent. It can also be done. Etching can also be performed with a laser.

  As shown in FIG. 3, the second electrode forming member 20 includes a second substrate 22 and a plurality (eight in this example) of second electrodes 24 formed on the second substrate 22. The second substrate 22 is also preferably configured using a material that is excellent in transparency, flexibility, insulation, and the like. The material constituting the second substrate 22 and the thickness of the second substrate 22 can be considered in the same manner as the first substrate 12. The second substrate 22 is disposed so as to face the first substrate 12 with a predetermined interval through a rectangular frame-shaped spacer 35. In addition, as the spacer 35, the double-sided adhesive tape which has a core material (polyethylene terephthalate film etc.) and the adhesive (acrylic adhesive paste etc.) each formed in the both surfaces can be used, for example. Alternatively, as the spacer 35, an ultraviolet curable adhesive, a thermosetting adhesive, or the like may be used. The thickness of the spacer 35 is set to 2 μm to 300 μm, for example.

  In the present embodiment, the second electrode 24 is formed on the back side (first electrode forming member 10 side) of the second substrate 22. The plurality of second electrodes 24 are arranged to face the plurality of first electrodes 14 with a predetermined interval (so-called air gap) in the Z-axis direction. The plurality of second electrodes 24 are arranged in parallel to each other so as to be arranged at a predetermined interval in the Y-axis direction. In the present embodiment, the second electrode 24 is formed in a stripe shape (a linear shape having a constant width). Note that the second electrode 24 may be formed in, for example, a wave shape or a zigzag shape. In any case, each of the second electrodes 24 is formed so as to extend along the X-axis direction as a whole. Thereby, the 1st electrode 14 and the 2nd electrode 24 are arrange | positioned so that it may mutually cross | intersect (this example orthogonally crosses) by planar view. Moreover, it is preferable that the 2nd electrode 24 is comprised using the material excellent in transparency. The material constituting the second electrode 24 and the thickness of the second electrode 24 can be considered in the same manner as the first electrode 14. The method for forming the second electrode 24 can also be considered in the same manner as the first electrode 14.

  The plurality of first electrodes 14 are each connected to a detection circuit (not shown) via a lead wiring. The plurality of second electrodes 24 are also connected to the detection circuit via routing wires. The routing wiring is configured using a metal such as gold, silver, copper, and nickel, or a conductive paste such as carbon.

  In the present embodiment, the touch panel 5 further includes a hard coat layer 26. The hard coat layer 26 is disposed on the foremost side of the touch panel 5, and specifically, adhered to the front side of the second substrate 22. The hard coat layer 26 preferably has transparency, scratch resistance, antifouling properties, and the like. Such a hard-coat layer 26 can be comprised using resin materials, such as a polyethylene terephthalate resin and an acrylic resin, for example. The 2nd board | substrate 22 and the hard-coat layer 26 are mutually bonded by the pressure sensitive adhesive (Pressure Sensitive Adhesive; PSA) etc., for example. Further, the hard coat layer 26 has an operation surface 26a on the front surface thereof. The operation surface 26 a is a surface that is touched (to be operated) by the user's finger or the like when the user inputs a predetermined operation to the electronic device 1.

  As shown in FIG. 3, the pressure sensitive layer 30 is provided so as to cover at least the entirety of the plurality of first electrodes 14. In the present embodiment, only one pressure-sensitive layer 30 is provided so as to cover only the entirety of the plurality of first electrodes 14. In other words, in this embodiment, the pressure sensitive layer 30 is not provided on the second electrode 24 side (see also FIG. 5). The pressure-sensitive layer 30 has a property that electrical characteristics change according to an external force (applied pressing force). Such a pressure sensitive layer 30 is configured using a composition including a binder 32 and a plurality of conductive particles 33 dispersed in the binder 32.

  The binder 32 is made of an insulating material, and disperses and holds the plurality of conductive particles 33 so that the conductive particles 33 do not conduct during normal times. The binder 32 is made of, for example, a resin material such as polyvinyl chloride resin, polyamide resin, polyester resin, polyacrylic resin, polyurethane resin, polyvinyl acetal resin, polyester urethane resin, cellulose ester resin, or alkyd resin. Can be configured. Especially, the resin material excellent in transparency can be used preferably. Further, as the binder 32, rubber, elastomer or the like may be used.

  The conductive particles 33 can be configured using, for example, a metal material. The conductive particles 33 themselves have a fixed shape that does not deform even when an external force is applied. The electroconductive particle 33 can be made into the metal particle which has an acicular irregular surface structure, for example. As the conductive particles 33, those that can be expected to have a quantum tunnel effect are preferably used. The conductive particles 33 are distributed and held in the binder 32 with a distribution density that does not affect the visibility and can be energized when pressed. As such a composition containing the binder 32 and the conductive particles 33, for example, a quantum tunneling composite material (Quantum Tunneling Composite) available under the trade name “QTC Clear” from Peratech Ltd. in the UK is used. Can be used.

  The pressure-sensitive layer 30 can be formed on the first substrate 12 by applying, for example, the above composition (referred to herein as a “QTC composition”). Examples of the method for applying the QTC composition include printing methods such as screen printing, offset printing, gravure printing, and flexographic printing. The thickness of the pressure-sensitive layer 30 (in particular, the thickness of the layer made of the binder 32 here) is thicker than the thickness of the first electrode 14, and is set to 1 μm to 5 μm, for example. In the present embodiment, since one pressure-sensitive layer 30 is provided so as to cover the entire plurality of first electrodes 14 as a whole, the pressure-sensitive layer 30 can be formed in a single process. With such a configuration, there is an advantage that the manufacturing process can be simplified as the entire touch panel 5.

  The pressure-sensitive layer 30 made of the QTC composition substantially functions as an insulator when no external force is applied (non-pressed state). For example, the pressure-sensitive layer 30 exhibits a resistance value of 1 MΩ or more in a non-pressed state. On the other hand, in a state in which an external force is applied (pressed state), a tunnel current flows between the plurality of conductive particles 33 that are close to each other regardless of the presence or absence of direct contact. Functions as a conductor. At this time, the resistance value (an example of electrical characteristics) of the pressure-sensitive layer 30 changes according to the magnitude of the external force. That is, the change in the resistance value of the pressure-sensitive layer 30 depends on the magnitude of the external force. For example, the pressure-sensitive layer 30 can exhibit a resistance value of less than 10 kΩ in the pressed state.

  The electronic device 1 including the touch panel 5 includes a control unit (not shown) including an arithmetic processing device such as a CPU, and the control unit is configured to perform position detection calculation and pressing force detection calculation. ing. Specifically, when a user's finger or the like is touched with respect to the touch panel 5 (operation surface 26a), the first electrode 14 and the second electrode 24 come into contact with each other at the touched location, and the electrodes 14, The resistance value between 24 changes. The control unit can determine the pressing position in the XY coordinate system on the operation surface 26a by detecting the change in the resistance value. When the user's finger or the like is touched on the touch panel 5 (operation surface 26a), as described above, the resistance value of the pressure-sensitive layer 30 changes according to the magnitude of the applied pressing force. The control unit can determine the magnitude of the pressing force applied in the direction (Z direction) orthogonal to the operation surface 26a by detecting a change in the resistance value of the pressure sensitive layer 30.

  By the way, the electroconductive particle 33 contained in the QTC composition used by this embodiment shows a particle size distribution as shown, for example in FIG. That is, the plurality of conductive particles 33 dispersedly arranged in the pressure-sensitive layer 30 have different particle sizes. In the present embodiment, the particle size of the conductive particles 33 varies within a range of 1 μm to 10 μm as an example. Although there is a mode value in the range of about 2 μm to 4 μm, conductive particles 33 having a particle size larger than the thickness of the pressure-sensitive layer 30 (in particular, the thickness of the layer made of the binder 32) are also included therein. Exists. For this reason, some conductive particles 33 are exposed from the surface on the front side of the pressure-sensitive layer 30 (here, in particular, a layer made of the binder 32) (see FIG. 5).

  Therefore, in this embodiment, as shown in FIG. 5, a protective layer 40 is provided between the pressure-sensitive layer 30 (here, a layer made of the binder 32) and the second electrode 24. In the present embodiment, only one protective layer 40 is provided so as to be in contact with the pressure-sensitive layer 30. More specifically, the protective layer 40 is provided so as to cover at least a part of the conductive particles 33 exposed from the surface of the pressure-sensitive layer 30. The protective layer 40 is made of a material that is softer than the material that forms the conductive particles 33. Moreover, it is preferable that the protective layer 40 is comprised using the material excellent in transparency. Furthermore, the protective layer 40 is preferably configured using a material having a high surface resistivity (for example, 1 MΩ / □ or more). Examples of materials that satisfy such requirements include resin materials containing metal oxide nanoparticles, conductive polymers, and the like.

  Examples of the metal oxide nanoparticles include titanium oxide, zinc oxide, aluminum oxide, niobium oxide, zirconium oxide, magnesium oxide, tin oxide, and ITO (Indium Tin Oxide). Among these, ITO nanoparticles can be preferably used. The particle size of the metal oxide nanoparticles is preferably 10 nm to 100 nm, for example. As the resin material containing metal oxide nanoparticles, an active ray curable resin such as an ultraviolet curable resin or an electron beam curable resin, or a thermosetting resin can be used. Examples of the ultraviolet curable resin include acrylic resins, epoxy acrylic resins, and alkoxy acrylic resins. Examples of the electron beam curable resin include urethane-modified acrylate resin and acrylic-modified polyester resin. Examples of the thermosetting resin include ethyl cellulose, phenol resin, epoxy resin, melamine resin, urea resin, unsaturated polyester resin, alkyd resin, polyurethane, and thermosetting polyimide.

  Examples of the conductive polymer include polyacetylene polymers, polyphenylene polymers, heterocyclic polymers, and ionic polymer polymers. Examples of the polyacetylene polymer include polyacetylene and polyphenylacetylene. Examples of the polyphenylene polymer include polyparaphenylene and polyphenylene vinylene. Examples of the heterocyclic polymer include PEDOT (polyethylenedioxythiophene) and polypyrrole. Examples of the ionic polymer polymer include polyaniline. Among these, PEDOT can be preferably used.

  In the present embodiment, the protective layer 40 provided between the pressure-sensitive layer 30 and the second electrode 24 functions as an “electrode protective layer” that protects the second electrode 24. As described above, when some conductive particles 33 having a large particle size are exposed from the surface of the pressure-sensitive layer 30, the second electrode 24 facing the pressure-sensitive layer 30 can be obtained by repeatedly using the touch panel 5. The exposed conductive particles 33 may be rubbed and damaged. However, by providing the protective layer 40 as the “electrode protective layer”, it is possible to suppress the second electrode 24 and the exposed conductive particles 33 from rubbing directly. The protective layer 40 is provided on the pressure-sensitive layer 30 so that the protective layer 40 and the second electrode 24 directly rub against each other, but the material constituting the protective layer 40 is made of conductive particles 33. Since it is softer than the constituent material, the second electrode 24 can be effectively prevented from being damaged. Moreover, it can also suppress effectively that the electroconductive particle 33 is damaged, or the electroconductive particle 33 peels from the pressure sensitive layer 30 (layer which consists of the binder 32). Therefore, a good pressure sensitive function can be maintained over a long period of time. In addition, since the protective layer 40 itself is not directly involved in the pressure-sensitive function, there is no particular problem even if the protective layer 40 is damaged.

  The thickness of the protective layer 40 is set smaller than the average interparticle distance A. Here, the average interparticle distance A is a concept representing the average value of the separation distance (interparticle distance D) between the conductive particles 33 adjacent to each other. More specifically, the average interparticle distance A is between the conductive particles 33 adjacent to each other for each of a plurality of sections C (see FIG. 6) that are virtually set dispersed in the pressure-sensitive layer 30. By determining the basic average interparticle distance B as the average value of the separation distance (interparticle distance D), and further calculating the average value (overall average value) of the basic average interparticle distance B determined for each section C Represents the distance to be determined.

  The method for determining the average interparticle distance A will be described in more detail with reference to the specific example of FIG. First, a laminate in which the pressure sensitive layer 30 is disposed on the first substrate 12 on which the first electrode 14 is formed is prepared. Next, a plurality (30 in the illustrated example) of sections C having a predetermined size (for example, 500 μm × 500 μm) are set in the laminate, and each section C is observed from the pressure-sensitive layer 30 side with an optical microscope. . The magnification in this case can be set to 150 to 750 times, for example. FIG. 6 schematically shows an enlarged view of a plurality (five in the illustrated example) of conductive particles 33 observed in one section C. Here, for convenience of explanation, the respective conductive particles 33 are distinguished by reference numerals “33a to 33e”. Further, the distance between two adjacent conductive particles 33 is represented by “D1 to D8” as follows.

Separation distance between the conductive particles 33a and the conductive particles 33b; D1
Separation distance between the conductive particles 33a and the conductive particles 33c; D2
Separation distance between the conductive particles 33b and the conductive particles 33c; D3
Distance between the conductive particles 33a and the conductive particles 33d; D4
Separation distance between the conductive particles 33b and the conductive particles 33e; D5
Distance between conductive particles 33c and 33d; D6
Distance between the conductive particles 33c and the conductive particles 33e; D7
Separation distance between the conductive particles 33d and the conductive particles 33e; D8

  Next, for each of the discovered conductive particles 33, the interparticle distance D between the other conductive particles 33 existing in the vicinity thereof is measured, and based on the obtained interparticle distance D, Other adjacent conductive particles 33 are specified. In this example, another conductive particle 33 having a minimum inter-particle distance D is specified as “an adjacent conductive particle 33”. For example, in the example of FIG. 6, when attention is paid to the conductive particles 33a, there are conductive particles 33b, 33c, 33d, and 33e in the vicinity thereof. Therefore, the interparticle distance D between the conductive particles 33b, 33c, 33d, and 33e and the conductive particles 33a is measured. Among them, the conductive particle 33b giving the minimum inter-particle distance D1 is specified as “the other adjacent conductive particle 33”, and the inter-particle distance D1 at that time is set as the “minimum separation distance with respect to the conductive particle 33a”. Sa ”. Similarly, regarding the conductive particles 33b, 33c, 33d, and 33e, the minimum separation distances Sb, Sc, Sd, and Se are determined.

Next, a basic average interparticle distance B that is an average value of the minimum separation distances S calculated for each conductive particle 33 is calculated. Specifically, the basic average interparticle distance B in the example of FIG. 6 is calculated as follows.
B = (Sa + Sb + Sc + Sd + Se) / 5
The basic average interparticle distance B calculated in this way represents the distance between any two adjacent conductive particles 33 in the section C.

The above procedure is executed for all the sections C, and the basic average interparticle distance B for each section C is calculated. Finally, the average interparticle distance A is calculated as the average value (overall average value) of the basic average interparticle distance B determined for each section C. Here, when the basic average interparticle distance B in the total 30 sections C in the example of FIG. 6 is represented by “B1 to B30”, specifically, the calculation is performed as follows.
A = (B1 + B2 + B3 +... + B30) / 30
The average interparticle distance A calculated in this way represents the distance between any two adjacent conductive particles 33 included in the entire pressure-sensitive layer 30.

  In this embodiment, since the thickness of the protective layer 40 is set to be smaller than the average interparticle distance A, it is difficult for the protective layer 40 to be energized in the X-axis direction and the Y-axis direction, and conversely in the Z-axis direction. The structure is easy to do. Supplementing this point, the resistance value in the energizing direction of interest in the protective layer 40 is proportional to the length in the direction and inversely proportional to the cross-sectional area in a plane orthogonal to the direction. Reducing the thickness of the protective layer 40 is equivalent to relatively reducing both the length in the Z-axis direction and the cross-sectional area in the YZ plane. Considering these together, by relatively reducing the thickness of the protective layer 40, the resistance value in the Z-axis direction is relatively reduced, and the resistance values in the X-axis direction and the Y-axis direction are relatively increased. can do. That is, in the protective layer 40, it is difficult to energize in the X-axis direction and the Y-axis direction, and conversely, energization is easy in the Z-axis direction.

  By relatively increasing the resistance value in the X-axis direction, it is easy to ensure insulation between the first electrodes 14 adjacent to each other. Thereby, a position detection function is implement | achieved appropriately. Further, by making the resistance value in the Z-axis direction relatively small, it is easy to ensure the energization between the first electrode 14 and the second electrode 24 via the pressure-sensitive layer 30 and the protective layer 40 at the time of pressing. . Thereby, a pressure-sensitive function is implement | achieved appropriately. Therefore, the position detection function and the pressure sensitive function are not impaired due to the provision of the additional protective layer 40.

Conceptually, the thickness of the protective layer 40 is preferably set so as to further satisfy the following criteria. That is, the thickness of the protective layer 40 is smaller than the average interparticle distance A,
(A) covering many exposed portions of the conductive particles 33;
(B) Energization in the thickness direction (Z-axis direction) of the protective layer 40 is ensured;
(C) Do not energize in the direction along the protective layer 40 (here, particularly in the X-axis direction),
(D) maintaining good visibility of the display device 4;
It is preferable to set so as to satisfy one or more of the following.

  The thickness of the protective layer 40 is preferably set so as to be larger than the average particle diameter of the conductive particles 33 based on the criterion (a). If it does in this way, about the many electroconductive particle 33, the whole part exposed from the surface of the pressure sensitive layer 30 (layer which consists of binders 32) can be covered with the protective layer 40. FIG. Further, with respect to the other conductive particles 33, many of the exposed portions can be covered with the protective layer 40. Therefore, it can suppress more effectively that the 2nd electrode 24 and the electroconductive particle 33 rub, and a pressure-sensitive function can be maintained further favorably. For example, it is preferable that the thickness of the protective layer 40 is set so as to be larger than the maximum particle diameter of the conductive particles 33. By setting in this way, the conductive particles 33 can be completely covered with the protective layer 40 so that the conductive particles 33 are not exposed from the surface of the pressure-sensitive layer 30 (layer consisting of the binder 32). The average particle size and the maximum particle size of the conductive particles 33 can be measured by, for example, a laser diffraction scattering method.

  However, by setting the thickness of the protective layer 40 larger, the continuity and transparency of the protective layer 40 may be affected. Therefore, the above criteria (b) to (d) are set in order to define a suitable upper limit value of the thickness of the protective layer 40.

  The thickness of the protective layer 40 is preferably set so as to be energized in the Z-axis direction and not energized in the X-axis direction based on the criteria of (b) and (c). For example, the thickness of the protective layer 40 is preferably set so that the resistance value in the Z-axis direction is less than 1 kΩ and the resistance value in the X-axis direction is 1 MΩ or more. Thereby, the electricity supply between the 1st electrode 14 and the 2nd electrode 24 via the pressure sensitive layer 30 and the protective layer 40 at the time of a press can be ensured appropriately. Moreover, the insulation between the 1st electrodes 14 which mutually adjoin can be ensured appropriately. Therefore, both the position detection function and the pressure sensitive function can be maintained well. Furthermore, the thickness of the protective layer 40 is preferably set so as to ensure a transmittance equal to or higher than a predetermined reference threshold based on the criterion (d). Thereby, the favorable visibility of the display apparatus 4 arrange | positioned at the back side of the touch panel 5 can be maintained.

  The thickness of the protective layer 40 is preferably set by comprehensively considering each of the above criteria (a) to (d). In this case, different weights may be set between the respective standards. For example, the criteria (b) to (d) may be more important than the criteria (a). In addition, the criteria (b) and (c) may be more important than the criteria (d). As an example, it is possible to cover as many conductive particles 33 as possible within a range in which the insulating property in the X-axis direction and the conductivity in the Z-axis direction in the protective layer 40 are sufficiently ensured and a certain degree of transparency is ensured. It is preferable that the thickness of the protective layer 40 is set so that it is possible. The thickness of the protective layer 40 depends on its constituent material, but can be set to 2 μm to 5 μm, for example.

  As described above, the touch panel 5 according to the present embodiment includes the protective layer 40 disposed between the pressure sensitive layer 30 and the second electrode 24 so as to be in contact with the pressure sensitive layer 30. For this reason, even when some conductive particles 33 having a large particle size are exposed from the surface of the pressure-sensitive layer 30, the protective layer 40 functions as an “electrode protective layer” and the second electrode 24 is damaged. Can be effectively suppressed. Moreover, it can also suppress effectively that the electroconductive particle 33 is damaged, or the electroconductive particle 33 peels from the pressure sensitive layer 30 (layer which consists of the binder 32). Therefore, a good pressure sensitive function can be maintained over a long period of time.

  The graph of FIG. 7 shows a comparison of FR characteristics before and after the durability test. In this figure, the bold line shows the FR characteristic when the touch panel 5 according to the present embodiment is used, while the thin line shows the FR characteristic when the touch panel without a protective layer is used as a comparative example. Show. Moreover, in each, the broken line has shown the FR characteristic in the test initial stage, On the other hand, the continuous line has shown the FR characteristic at the time of completion | finish of a test. Referring to the graph of FIG. 7, in the touch panel 5 according to the present embodiment including the protective layer 40, the change amount of the resistance value before and after the durability test is suppressed smaller than that of the touch panel of the comparative example. Can be easily understood. Thereby, it was confirmed that a favorable pressure-sensitive function can be maintained over a long period of time.

  In this durability test, an improvement in the detection accuracy of the pressing force was recognized as an unexpected effect due to the provision of the protective layer 40. This is considered to be because the exposed height of the conductive particles 33 from the surface of the pressure-sensitive layer 30 is reduced and the surface roughness of the pressure-sensitive layer 30 is improved by providing the protective layer 40. Thereby, the detection sensitivity of the pressing force can be stabilized, and it is considered that the detection accuracy of the pressing force is improved as a result.

[Other Embodiments]
Finally, other embodiments of the touch panel according to the present invention will be described. Note that the configurations disclosed in the following embodiments can be applied in combination with the configurations disclosed in other embodiments as long as no contradiction arises.

(1) In the above embodiment, the configuration in which one protective layer 40 is provided on the pressure-sensitive layer 30 has been described as an example. However, the embodiment of the present invention is not limited to this. If it is between the pressure sensitive layer 30 and the second electrode 24, for example, as shown in FIG. 8, one protective layer 40 is provided on the second substrate 22 so as to cover the whole of the plurality of second electrodes 24. May be. Even with such a configuration, it is possible to prevent at least the second electrode 24 and the exposed conductive particles 33 from being damaged. Therefore, the same effect as the above embodiment can be obtained. For example, as shown in FIG. 9, two protective layers 40 may be provided, one on each of the pressure-sensitive layer 30 and the second substrate 22. In this case, the thicknesses of the two protective layers 40 are preferably set so that each of the above criteria (a) to (d) is achieved in a well-balanced manner by the sum of them.

(2) In the above embodiment, the configuration in which only one pressure-sensitive layer 30 is provided so as to cover the entirety of the plurality of first electrodes 14 has been described as an example. However, the embodiment of the present invention is not limited to this. For example, two pressure sensitive layers 30 may be provided so as to cover the entire plurality of second electrodes 24 in addition to the entire plurality of first electrodes 14. Even in this case, since some of the conductive particles 33 are exposed on the surface of each pressure-sensitive layer 30, at least the conductive particles 33 may be damaged or peeled off. For this reason, by providing at least one protective layer 40 between the two pressure-sensitive layers 30 (also between the pressure-sensitive layer 30 on the first substrate 12 side and the second electrode 24), Similar effects can be obtained. Of course, a total of two protective layers 40 may be provided on each pressure sensitive layer 30 so as to cover each of the two pressure sensitive layers 30.

(3) In said embodiment, the 1st electrode formation member 10, the pressure sensitive layer 30, the protective layer 40, and the 2nd electrode formation member 20 are the structures arrange | positioned in order of description toward the front side from the back side. Described as an example. However, the embodiment of the present invention is not limited to this. For example, as shown in FIG. 10, the first electrode forming member 10, the pressure sensitive layer 30, the protective layer 40, and the second electrode forming member 20 may be arranged in the order described from the front side to the back side. In this case, the first electrode forming member 10, the pressure-sensitive layer 30, and the protective layer 40 are laminated in the order described from the front side to the back side, and the second electrode forming member 20 is on the back side with respect to the protective layer 40. It may be arranged on the side with a predetermined interval. Further, a hard coat layer 26 may be provided on the front side of the first substrate 12.

(4) In the above-described embodiment, an example in which the thickness of the protective layer 40 is set in consideration of the respective criteria (a) to (d) described above has been described. However, the embodiment of the present invention is not limited to this. The thickness of the protective layer 40 only needs to be set at least smaller than the average interparticle distance A, and one or more of the criteria (a) to (d) may not be considered at all.

(5) In the above embodiment, a value serving as a basis for calculating the basic average interparticle distance B that represents the distance between any two adjacent conductive particles 33 in the section C is set for each conductive particle 33. An example in which the minimum separation distance S is used has been described. However, the embodiment of the present invention is not limited to this. For example, the basic average interparticle distance B may be calculated based on the average separation distance for each conductive particle 33. Here, the average separation distance represents an average value of the interparticle distance D between one or more conductive particles 33 existing in the vicinity. Alternatively, not only the average separation distance but also a value obtained by performing statistical processing on the interparticle distance D between one or more conductive particles 33 existing in the vicinity (for example, median value, weighted average value, etc.) Based on this, the basic average interparticle distance B may be calculated.

(6) In the above embodiment, the plurality of first electrodes 14 are arranged in parallel so as to be arranged in the X-axis direction, and the plurality of second electrodes 24 are arranged in parallel to each other so as to be arranged in the Y-axis direction. Was described as an example. However, the embodiment of the present invention is not limited to this. The method of taking the X-axis direction and the Y-axis direction is arbitrary, and the plurality of first electrodes 14 are arranged in parallel so as to be arranged in the Y-axis direction, and the plurality of second electrodes 24 are arranged in the X-axis direction. They may be arranged parallel to each other. In this case, the Y-axis direction corresponds to the “first direction” in the present invention, and the X-axis direction corresponds to the “second direction” in the present invention.

(7) In the above embodiment, the configuration in which the touch panel 5 includes the hard coat layer 26 has been described as an example. However, the embodiment of the present invention is not limited to this. For example, such a hard coat layer 26 may not be provided on the touch panel 5. In this case, the surface on the front side of the second substrate 22 is an operation surface that is touched (operated) by a user's finger or the like.

(8) Regarding other configurations, it should be understood that the embodiments disclosed herein are illustrative in all respects and that the scope of the present invention is not limited thereby. Those skilled in the art will readily understand that modifications can be made as appropriate without departing from the spirit of the present invention. Accordingly, other embodiments modified without departing from the spirit of the present invention are naturally included in the scope of the present invention.

  The present invention can be used for, for example, a touch panel mounted on a multi-function mobile phone.

5: Touch panel 10: First electrode forming member 12: First substrate 14: First electrode 20: Second electrode forming member 22: Second substrate 24: Second electrode 30: Pressure sensitive layer 32: Binder 33: Conductive particles 40: Protective layer C: Section D: Interparticle distance S: Average separation distance B: Basic average interparticle distance A: Average interparticle distance

Claims (5)

A plurality of first electrodes arranged in parallel to each other so as to be aligned in a first direction;
A plurality of second electrodes opposed to the plurality of first electrodes and arranged in parallel to each other so as to be aligned in a second direction intersecting the first direction;
A pressure-sensitive layer comprising a composition containing a plurality of conductive particles having different particle diameters dispersed in a binder, covering at least a plurality of the first electrodes, and having electrical characteristics that change according to an external force;
A protective layer provided between the pressure-sensitive layer and the second electrode, having a thickness smaller than an average inter-particle distance representing an average value of a separation distance between the conductive particles adjacent to each other;
Touch panel equipped with.   The touch panel as set forth in claim 1, wherein the thickness of the protective layer is set so as to energize in the thickness direction and not in the first direction.   The touch panel according to claim 1 or 2, wherein a thickness of the protective layer is set larger than an average particle diameter of the conductive particles.   The touch panel as described in any one of Claim 1 to 3 with which the said protective layer is comprised with the material softer than the material which comprises the said electroconductive particle. One pressure-sensitive layer is provided so as to cover only the entirety of the plurality of first electrodes,
The touch panel as described in any one of Claim 1 to 4 with which the one said protective layer is provided so that the said pressure-sensitive layer may be contact | connected.

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