JP6003293B2 - Method for manufacturing film-type capacitive touch panel - Google Patents

Description

  The present invention relates to a film-type capacitive touch panel using a mesh structure of metal wiring as a sensor, and more particularly to a technique for manufacturing a film-shaped sensor having an anti-oxidation function for metal wiring by a roll-to-roll method.

  2. Description of the Related Art In recent years, touch panel type input devices (hereinafter simply referred to as touch panels) have been adopted for operation units of various electronic devices such as mobile phones, portable information terminals, and car navigation systems. The touch panel is used as an input device that detects a contact position of a fingertip or a pen tip on a display surface of a display panel such as a liquid crystal display device or an organic EL device. There are various types of touch panels, such as a resistance film type and a capacitance type, depending on the structure and detection method.

  There are two types of capacitive touch panels: surface type and projection type. Both methods detect the position by capturing the change in capacitance between the fingertip and the conductive film. Since electrostatic coupling occurs just by moving the finger close to the sensor surface, it is possible to display a cursor before contact. The object to be pressed needs to be a finger or an electrostatically conductive material equivalent to that of the finger, but the alternating current that flows in accordance with the change in the capacitance does not depend on the impedance of the contact medium.

  In particular, the projected capacitive method can detect multiple points of the fingertip. In general, the projection type has a configuration in which a support substrate on which an electrode layer and a control IC are mounted is covered with a protective insulating resin. Although the details of the electrode layer are omitted, on the support substrate such as glass or plastic, a large number of mosaic electrodes composed of one set of X and Y direction electrodes are formed on a support substrate such as glass or plastic using a transparent electrode material (ITO). Yes. The X direction electrode and the Y direction electrode are all laid while maintaining insulation (Patent Documents 1 and 2).

  Further, as shown in FIG. 1, stripe-shaped metal wirings 2 extending in the vertical direction and metal wirings 3 extending in the horizontal direction may be laid on the substrate while maintaining insulation (Patent Documents 3 and 4). Metal wiring is more advantageous because it has lower sensitivity than ITO, but metal is light-shielding and reflective, so unlike ITO, wiring density and aperture ratio are problematic. Whether the ITO array or the metal array is touched or approached, the change in the capacitance of the electrode in the vicinity can be known from one set of vertical and horizontal electrode rows, so that the contact position can be specified fairly accurately, except for the resolution.

  Many points can be detected by a large number of electrode rows running vertically and horizontally. However, since the number of terminals is large, the wiring is thin and the resistance of the ITO wiring is too high. Therefore, in a large-sized touch panel, in order to connect an FPC on which an IC for position detection is mounted and a sensor substrate, a wiring with a large line width is provided around the substrate. There is a tendency for the cost to increase, for example, it is necessary to have a three-layer structure of molybdenum / aluminum / molybdenum or silver paste.

  Therefore, as a touch panel for a large display with a diagonal size of 15 inches or more, the metal wiring type from the beginning has lower resistance, and it is also practical to lay the metal wiring on the film at a low cost. Can be said to be expensive. However, simply forming a light-shielding metal wiring such as a thin copper wire as a sensor electrode on the film has a problem that the resistance value of the metal wiring increases with time. When the wiring resistance increases, there is a problem that the sensitivity as a position sensor decreases and the operation becomes unstable. On the other hand, there is a problem in that the visibility is lowered by forming a gap only by covering the metal wiring with another film.

  Conventionally, as a means for suppressing the change with time, there is a technique in which a metal wiring is covered with a protective film or a silica-based sol-gel solution is formed into a film as a spin coat and then patterned by a photolithography method. Moreover, generally the protective layer itself is based on a film base material, such as laminating and bonding with a PSA non-carrier film, and it is mostly bonded to a touch panel. Manufacturing two functional films and bonding them together has a problem that the process is troublesome and the process is complicated and foreign matter and bubbles are involved, resulting in a decrease in yield due to problems in the process. Moreover, since the product form after bonding is a sheet form, there existed a difficulty that a roll-to-roll construction method could not be consistent in finishing a touch panel.

  In addition to film-like touch panels, liquid crystal display devices require various functional films such as polarizing films, antireflection films, and antiglare films. When these are combined with touch panels, the thickness of the touch panel is as uniform as possible. A simple roll has an advantage that the degree of freedom is high in processing.

JP 2012-01462 A JP 2012-004042 A JP 2011-253263 A JP 2011-248722 A

  The present invention has been made in view of the above problems, and it is possible to efficiently form a protective layer that suppresses a change in metal resistance with time, and to use a metal mesh having a higher degree of freedom in processing in a later process as a sensor. It was an object to provide a method for manufacturing a capacitive touch panel.

The invention according to claim 1 for achieving the above object is as follows:
Forming striped copper wiring on the front and back surfaces of the roll film so as to be orthogonal to each other on the front and back;
Applying an ionizing radiation curable composition to the surface of the roll film to form a coating film;
Irradiating the coating with ionizing radiation to form a cured coating;
Have a in this order,
The film is a protective film made of an acid-free organic resin,
A method of manufacturing a film-like capacitive touch panel, characterized in that the surface resistance of the copper wiring is set to 3Ω / □ or less and the capacitance between the upper and lower copper wirings is set to a range of 0.5 to 3 pF. is there.

  According to the first and second aspects of the present invention, the film obtained by curing the ionizing radiation curable resin covers the metal wiring arranged in a stripe shape as the protective film, and the metal does not directly contact air. Oxidation due to moisture and oxygen is suppressed.

  Production of the metal mesh and formation of the protective film are all performed in a roll-to-roll manner, resulting in a significant improvement in productivity, and the film-like touch panel after the formation of the protective film is obtained in a roll form rather than a cut sheet form. The effect of increasing the degree of freedom in the post-process can be expected.

  As a result of forming the resin protective film directly on the film on which the metal wiring is formed, a thin touch panel can be efficiently manufactured by reducing man-hours and eliminating an extra film substrate.

It is a figure of the top view explaining the wiring arrangement (mesh structure) of the touch panel which uses a metal. It is a figure of the cross sectional view explaining the structure of the touch panel which becomes this invention. (A)-(f) It is process drawing of the cross sectional view explaining the manufacturing process of the touchscreen which becomes this invention.

  Hereinafter, embodiments of the touch panel according to the present invention will be described with reference to the drawings.

  The metal wiring pattern of the touch panel according to the present invention is shown in FIG. 1 in a top view, and the structure is shown in FIG. 2 in a sectional view. The striped copper wirings 2 and 3 having the same pitch are arranged on the front and back surfaces of the film base 5 so as to be orthogonal to each other, and the opening 4 has a generally square mesh structure when viewed from above. is there. The solid line corresponds to the striped metal wiring 3 on the front surface, and the double line corresponds to the metal wiring 2 on the back surface. Further, the metal wirings 2 and 3 on the front and back of the film are covered with a protective film 7 obtained by curing an organic resin.

  Since the insulating film base 5 is between the metal wiring 2 and the metal wiring 3, the upper and lower metal wirings 2 and 3 are naturally insulated. Two sets of films having stripe electrodes on only one surface may be prepared and pasted back to back. The present invention can also be applied to a structure in which a mesh structure is provided only on one surface.

  Since the metal wiring has a light-shielding property, if the line width d is increased, the aperture ratio is decreased and the transmittance is decreased. If the stripe pitch p is increased, the resolution as the position sensor is decreased. Therefore, the line width d and the pitch p are decreased. Is set to an appropriate value. As the metal material, aluminum or copper is preferable, but copper is most preferable in terms of resistance and cost.

  A touch panel is a grounding device when an electrostatic and conductive medium such as a finger or hand is brought close to a conductor when alternating current with the same phase and voltage is applied to both ends of the conductor such as metal wiring. This is an electronic device that utilizes the phenomenon that capacitive coupling occurs between a medium that is considered to be conductive and a conductor (which is also grounded) and an excessive alternating current flows through the conductor.

  Therefore, it is not necessary for the finger to touch the conductor directly, and the conductor may be contacted or approached via the dielectric. Since the conductor is soiled when the hand touches the conductor of the sensor portion, it is usually necessary to coat the conductor with an antifouling transparent protective material. The conductors (hereinafter also referred to as electrodes) are not necessarily present on the same plane, and may be disposed between the insulating resins 5 as shown in FIG. However, since the substantial distance to the contact medium (for example, the finger) changes, there is a possibility that the sensitivity changes depending on whether the sensitivity is above or below the insulating resin 5.

  In principle, it is possible to detect which electrode material is close to which side by simply placing the electrode material appropriately, but in order to maintain accuracy as a position sensor, linear electrodes are arranged in an XY matrix. Thus, the position is calculated from the intersection by independently detecting which X-direction electrode and which Y-direction electrode, not where on which electrode. Of course, all of the electrodes 2 in the X direction and the electrode 3 in the Y direction need to be insulated. Moreover, the electrodes 2 and 3 do not necessarily need to be linear. In the case of a light-shielding metal wiring, fine lines that are difficult to see within the range allowed by the transmittance are arranged as tightly as possible.

Although it does not specifically limit as a formation means of the organic resin layer (henceforth a protective film only) used as a protective film, It must be able to form a resin layer on a film by a roll-to-roll system. It is also preferable that the protective film 7 can be formed in a pattern so as to cover the sensor electrode portion and not the portion used for connection of the extraction electrode 6. Further, it is preferable that the protective film fills the gap between the stripe electrodes and covers the surface, and the surface of the protective film is generally flush as shown in FIG. If the thickness of the copper wires 2 and 3 is about 10 to 15 μm, the thickness of the protective film 7 is optimally about 20 to 25 μm.

  The size of the transparent portion of the touch panel is used so as to overlap with an image display unit such as a liquid crystal display or an organic EL, so that it is at least as large as these image display units. However, if the entire range is not the input range of the touch panel, the mesh electrode may be omitted even if the range is a fluoroscopic range. In general, it is preferable to paint in a frame shape so that it is not visible outside the range that requires fluoroscopy (decoration).

  The individual copper wirings 2 and 3 constituting the mesh electrode are all guided to the outer periphery of the film base 5 and connected to terminals for external connection. The wiring 6 is called a lead-out wiring and is preferably made of copper with low cost and low resistance. In a portion that is not seen through, the line width can be increased within an allowable range. In this case, a range of approximately 0.02 to 0.5 mm is preferable. The mesh-like copper wirings 2 and 3 and the drawing copper distribution wiring 6 are collectively formed from a copper thin film laminated on the film 5. All copper wiring needs to be insulated from each other as long as they are used as sensors.

  Assuming that the width of the opening 4 of the mesh partitioned by the copper wiring is p and the wiring width of the light shielding portion is d, d / p = 0.05 when the aperture ratio is 90%, and d / p = 0. It is about 01. Since the line width d of the light-shielding metal is said to be invisible when it is approximately 20 μm or less, the side p of the opening is in the range of 400 to 2000 μm when the line width d = 20 μm. The narrower line width d = 10 μm needs to be in the range of 200 to 1000 μm, and d = 5 μm in the range of 100 to 500 μm. For large displays, the line width is preferably about 50 μm or less, and the aperture ratio is 90%, and p is about 1000 μm or more.

  The surface resistance of the copper wiring is preferably set to about 3Ω / □ or less. This is because the sensor sensitivity is higher when the resistance is lower. Further, since the film 5 having a thickness of about 100 μm is interposed between the upper and lower metal wirings 2, 3, the capacitance is preferably set in the range of 0.5 to 3 pF.

  Incidentally, the surface resistance was 0.3Ω / □ (by the four-terminal method) when the electrolytic copper foil was etched to form a mesh structure having a thickness of 13 μm, a line width of 10 μm, a pitch of 1000 μm, and an aperture ratio of 98%. The deposited copper foil had a thickness of 1.5 μm, a line width of 5 μm, a mesh pitch of 250 μm (substantially corresponding to the aforementioned p), an aperture ratio of 93%, and a surface resistance of 3Ω / □. Although there are material differences in manufacturing method, the surface resistance can be controlled to a desired value within a range of 3Ω / □ or less.

  If the metal wiring 2 and 3 made of copper is laid on the film 5, the surface and side surfaces of the copper wiring are exposed to the atmosphere, and the resistance increases gradually due to oxidation of the copper surface by moisture and oxygen in the air. To do. Under an acceleration condition of 85 ° C. and 95% RH, the resistance increases by about 20% after 1000 hours. Since an increase in resistance causes a decrease in sensitivity, it is not preferable and must be suppressed.

  In the present invention, as shown in FIG. 2, the surfaces of the metal wirings 2 and 3 are preferably completely covered with a protective film 7 made of an acid-free organic resin so as not to come into contact with air. As a means for forming an organic resin coating film on a film, a roll-to-roll method may be applied. A die coating method in which resin ink is dropped onto a film from a nozzle having a predetermined width or a method in which resin ink is transferred from a cylinder plate. Any of these may be used. As the printing method, an intaglio printing method such as gravure printing, offset printing, flexographic printing or the like can be appropriately selected and used. The method of dropping from the nozzle can be selected from die coating, slit die coating, lip coating and the like. In any case, a coating film having a thickness ranging from several μm to 50 μm can be formed.

  The ionizing radiation curable composition that constitutes the organic resin layer is a curable composition that is used after being crosslinked and cured by ionizing radiation energy such as electromagnetic waves, ultraviolet rays, visible rays, and electron beams. In the case of curing by ultraviolet irradiation, a high pressure mercury lamp light source containing light having a wavelength in the range of 150 to 450 nm is used. In the case of electron beam curing, an electron beam with an irradiation voltage of 3 to 300 kGy in an acceleration voltage range of 10 to 500 kV, more preferably 30 to 200 kV is required.

  Specific examples of the curable composition include a (meth) acrylate-based composition, and a mixture of a prepolymer, an oligomer and a monomer having a polymerizable unsaturated bond or an epoxy group in the molecule is used. Examples of the prepolymer and oligomer include unsaturated polyesters, methacrylates, acrylates, and cationically polymerizable epoxy compounds.

  Examples of the monomer include compounds such as ethylene glycol diacrylate and propylene glycol diacrylate, polyfunctional compounds such as dipropylene glycol diacrylate, and polythiol compounds. In addition, a polymerization initiator or the like is necessary.

  For transparent film base materials, PET is preferable from the viewpoint of cost, but cellulose resins such as cellulose diacetate and cellulose triacetate, polyethylene resins, polypropylene resins, methacrylic resins, cyclic polyolefin resins, polystyrene resins, acrylonitrile- (Poly) styrene copolymer (AS resin), acrylonitrile-butadiene-styrene copolymer (ABS resin), polyvinyl chloride resin, poly (meth) acrylic resin, polycarbonate resin, polyester resin, polyamide resin Further, a thermoplastic resin film having a thickness of 50 to 150 μm manufactured from a polyamideimide resin or the like can be used.

  Next, a manufacturing method of the touch panel will be described with reference to the process diagram of FIG.

  A film-like touch panel with a protective film was manufactured by a roll-to-roll method using a PET film with an electrolytic copper foil having a thickness of 100 μm and a width of 300 mm.

  On the PET film, an electrolytic copper foil having a smooth surface having a thickness of 12 μm is laminated on the front and back surfaces through an adhesive having a thickness of 6 μm. Since the line width of the copper wire formed by etching the copper foil cannot be made thinner than the thickness of the copper foil, it is necessary to determine the type and thickness of the copper foil from the desired line width. When the line width is as thin as about 10 μm or less, it is preferable to use a copper thin film deposited on the film. Other than the electrolytic copper foil, a rolled copper foil can also be used.

  First, a roll-shaped PET film 5 in which a copper foil 11 having a thickness of 12 μm was laminated on both sides was prepared (FIG. 3A), and patterning of the copper foil was performed by applying a regular photolithographic method. In FIG. 3, the adhesive layer is omitted, and the film is drawn like a sheet but is in the form of a long roll. The arrows in the figure schematically indicate the moving direction of the film substrate 5.

The negative resist 12 was applied to the upper copper foil 11 surface with a thickness of about 6 μm using a roll coater 13 and dried at 90 ° C. for 30 minutes (FIG. 3B). Next, UV light was irradiated at about 100 mJ / cm ² through a photomask provided with a stripe pattern constituting the mesh portion and an extraction electrode pattern. The other film surface was coated with resist 12 with the same thickness, and then exposed through a photomask. As a resist, a casein resist can be used in addition to a general-purpose dry film type negative resist.

The photoresist layer was then developed with a 3% aqueous sodium carbonate solution. Thereby, a resist pattern is formed in a portion corresponding to the stripe pattern of the copper wiring,
The rest of the resist was removed.

  Next, using a ferric chloride solution having a specific gravity of 1.45, the exposed portions of the copper foil were etched away at the same time, and the remaining resist was peeled off. As a result, stripe-shaped metal wirings 2 and 3 having a mesh structure in the top view were formed on the front and back of the film substrate 5, and at the same time, wiring 6 was also formed on the outer peripheral portion so as to lead out (FIG. 3C). .

  PETA (light acrylate PE-3A; solid content concentration 100%) was used as the organic resin for the protective film, and the solid content concentration was diluted to 50% using IPA as a solvent. As a curing agent, Irgacure 18 (manufactured by Ciba Specialty Chemicals Co., Ltd.) was added at 5% to PETA for adjustment. Furthermore, 0.1% of fluorine-based additive F-470 (DIC Corporation 9) was added to the solid content to obtain a resin ink for a protective film.

After coating the above protective film ink on one surface of the PET film with a gravure coater 14 to a film thickness of 30 μm (FIG. 3D), the dried coating film was passed through a drying chamber (not shown). Obtained. Thereafter, the coating film was cured by irradiating ultraviolet rays 15 having a main wavelength of 365 nm and an irradiation intensity of 40 mJ / cm ² · sec for 40 seconds from the 250 W ultra-high pressure mercury lamp provided (FIG. 3E). After the film was rolled up and rolled, the same process was repeated on the metal wiring on the other side to obtain a film-like touch panel in which both surfaces of the film were covered with the protective film 7 (FIG. 3 (f)).

  In this way, a capacitive touch panel provided with a protective film by a consistent roll-to-roll method could be manufactured in a roll shape.

1. Metal wiring mesh arrangement 2, stripe electrode 3 in X direction, stripe electrode 4 in Y direction, opening 5, film base material (insulating resin)
6, lead-out wiring 7, protective layer (ionizing radiation curable composition)
9, intersection 10, touch panel 11, copper foil 12, resist 13, roll coater 14, gravure coater p; opening width d; wiring width

Claims (1)

Forming striped copper wiring on the front and back surfaces of the roll film so as to be orthogonal to each other on the front and back;
Applying an ionizing radiation curable composition to the surface of the roll film to form a coating film;
Irradiating the coating with ionizing radiation to form a cured coating;
Have a in this order,
The film is a protective film made of an acid-free organic resin,
A method of manufacturing a film-type capacitive touch panel , comprising setting a surface resistance of a copper wiring to 3Ω / □ or less and a capacitance between upper and lower copper wirings in a range of 0.5 to 3 pF .

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