JP5416682B2 - Touch panel sensor and manufacturing method thereof - Google Patents

Description

  The present invention relates to a touch panel sensor having a transparent conductive film and wiring connected to the transparent conductive film.

  The touch panel sensor, used as an input switch integrated with the image display device, is located on the front of the image display device. Due to its ease of use, the touch panel sensor is widely used for bank ATMs, ticket vending machines, car navigation systems, PDAs, and copy machine operation screens. It is used. Examples of the input point detection method include a resistance film method, a capacitance method, an optical method, an ultrasonic surface acoustic wave method, and a piezoelectric method. Of these, the resistive film type and the capacitive type are most widely used because they are not costly and have a simple structure.

  A capacitive touch panel sensor has a configuration in which a transparent conductive film is formed on the front and back surfaces of a single substrate (for example, a glass substrate or a film substrate) in the X-axis direction and the Y-axis direction, respectively. It has a structure protected by a protective layer (for example, glass or film). When the protective layer in the touch panel sensor having such a configuration is touched with a finger, a pen, or the like, a capacitance change occurs with the transparent conductive film, and the touched position is detected by detecting this change. .

  In the process of manufacturing the touch panel sensor, the wiring such as the lead wiring for connecting the transparent conductive film and the control circuit and the metal wiring for connecting the transparent conductive film is generally conductive paste such as silver paste or conductive ink. Is formed by printing with an inkjet or other printing method. However, wiring made of pure silver or a silver alloy has poor adhesion to glass, resin, etc., and causes aggregation due to aggregation on the substrate at the connection portion with an external device, leading to defects due to increased electrical resistance or disconnection. There is a problem such as.

  Furthermore, the touch panel sensor is a sensor that senses contact with a human finger or the like, and the screen is slid with a finger or the like, and a temporary deflection occurs due to stress applied at the time of touch. Due to repeated use of the touch panel, this deflection is repeatedly generated, and stress is repeatedly applied to the wiring. Accordingly, the wiring is particularly required to have durability (resistance to stress). However, it is difficult to say that the wiring formed using a conductive paste made of pure silver or a silver alloy has sufficient durability, and the wiring is easily damaged during use of the touch panel. If the wiring is damaged, the electrical resistance of the wiring increases and a voltage drop occurs, so that the accuracy of position detection of the touch panel sensor tends to decrease. Further, when the pen touch method is adopted, it is necessary to reduce the pitch of the wiring. However, when the paste is used, it is difficult to reduce the pitch because it is formed by a coating method.

  On the other hand, it is also conceivable to apply pure Al having a sufficiently low electrical resistivity to the wiring material. However, when pure Al is used as the wiring material, there arises a problem that insulating aluminum oxide is formed between the transparent conductive film and the pure Al film in the touch panel sensor, and electrical conductivity cannot be ensured. Therefore, in order to prevent Al oxidation and ensure electric conductivity, a barrier metal layer made of a refractory metal such as Mo or Ti is used as a base layer by interposing between a transparent conductive film and a pure Al film. A method of using an Al—Nd alloy containing Nd having excellent heat resistance instead of pure Al has been proposed. Further, the applicant of the present invention shows an Al film containing a predetermined amount of Ni and / or Co as an Al film that exhibits low electrical resistance even when directly connected to a transparent conductive film, and that hardly increases in electrical resistance or breaks over time. A Ni / Co alloy film (single-layer wiring material) is disclosed in Patent Document 1.

JP 2009-245422 A

  An object of the present invention is to provide a highly reliable touch panel sensor that is particularly excellent in durability in the lateral direction and is less likely to cause disconnection or increase in electrical resistance over time.

  The touch panel sensor of the present invention capable of solving the above problems is a touch panel sensor having a transparent conductive film and a wiring connected to the transparent conductive film, wherein the wiring is in order from the substrate side, a refractory metal film, and an Al alloy. The Al alloy film contains a rare earth element in an amount of 0.05 to 5 atomic%, and has a Young's modulus of 80 to 200 GPa. The main point is that the maximum value of the diameter (Feret diameter) is 100 to 350 nm.

  In a preferred embodiment of the present invention, the rare earth element is one or more elements selected from the group consisting of Nd, Gd, La, Y, Ce, Pr and Dy.

  In a preferred embodiment of the present invention, the transparent conductive film is made of indium tin oxide (ITO) or indium zinc oxide (IZO).

  According to the present invention, in a touch panel sensor using a wiring material in which a refractory metal film is disposed above and below an Al alloy film containing a rare earth element as a touch panel sensor wiring, the Young's modulus and crystal of the Al alloy film are used. Since the maximum value of the constant direction tangent diameter (Feret diameter) of the grain is appropriately controlled, it is particularly excellent in durability in the lateral direction, and it is difficult to cause disconnection or increase in electrical resistance over time, and reliability. We were able to provide a high touch panel sensor. The touch panel of the present invention is suitably used for a capacitive touch panel sensor that is operated by tracing the screen in multiple directions with a finger or the like, such as a portable game machine or a tablet computer.

  The present inventors have widely used wiring materials as touch panel sensor wirings, that is, Al alloy films containing rare earth elements (hereinafter sometimes abbreviated as Al-rare earth element alloy films or simply Al alloy films). The touch panel sensor having a wiring material in which a refractory metal film such as Mo is laminated above and below is particularly suitable for lateral deformation caused by deflection applied when touched with a human finger or pen. In order to provide a wiring material that has resistance, can prevent disconnection and peeling, and further can prevent an increase in electrical resistance with time, it has been studied. As a result, as the Al-rare earth element alloy film, an Al alloy film having a predetermined Young's modulus and a maximum value of the tangential diameter (Feret diameter) of crystal grains (hereinafter sometimes abbreviated as the maximum grain size). As a result, it was found that the intended purpose was achieved, and the present invention was completed.

  That is, the characteristic part of the present invention is that an Al alloy film having a Young's modulus of 80 to 200 GPa and a maximum particle size of 100 to 350 nm is adopted as an Al-rare earth alloy film for wiring used together with a refractory metal film. is there.

  First, the Young's modulus of the Al-rare earth alloy film is 80 to 200 GPa. The touch panel is excellent in deformability (followability) when touched (in use), especially when the screen is bent with a finger or the like, and stress is temporarily concentrated on the sensor edge. It is also required to have durability in the lateral direction to such an extent that disconnection, breakage, peeling, etc. of the wiring does not occur even if the wire is deformed or deteriorates. The Young's modulus is set from such a viewpoint, and is set in consideration of the balance with the Young's modulus of the refractory metal films disposed above and below the Al alloy film.

  Specifically, when the Young's modulus of the wiring material constituting the wiring is small (too soft), the wiring is repeatedly deformed due to stress concentration, and the wiring deteriorates, causing breakage, peeling, etc., and increasing the electric resistance. Such a problem may occur. On the other hand, when the Young's modulus of the wiring material is large (too hard), deformation is difficult to occur with respect to the indentation load, so that deterioration such as microcracking or peeling may occur. Further, when a laminate of an Al alloy film and a refractory metal film is used as a wiring material as in the present invention, when setting the Young's modulus of the Al alloy film, the balance with the Young's modulus of the refractory metal film is further increased. It is necessary to consider that the upper limit of the Young's modulus of the Al alloy film should be controlled to be approximately the same as the Young's modulus of the refractory metal constituting the refractory metal film, while the lower limit of the Young's modulus of the Al alloy film It is better that the difference in Young's modulus of a substrate typified by a glass substrate is not so great. Based on such a viewpoint, in the present invention, the Young's modulus of the Al alloy film is set to 80 GPa or more and 200 GPa or less. Preferably, it is 85 GPa or more and 180 GPa or less. The Young's modulus of the Al alloy film is a value measured by the method described in the examples described later.

  Furthermore, the maximum particle diameter [maximum value of the tangential diameter (Feret diameter) of crystal grains] of the Al alloy film used in the present invention satisfies 100 to 350 nm. As described above, in the present invention, it is necessary to control the Young's modulus of the Al alloy film within a predetermined range. Normally, the Young's modulus is generally closely related to the maximum particle size, and the rare earth element content is When it is within the range of the invention (5 atomic% or less), the Young's modulus tends to decrease as the maximum particle size increases. In the present invention, from the viewpoint of securing the lower limit of the Young's modulus of the Al alloy film (80 GPa), the upper limit of the maximum particle size is set to 350 nm, and from the viewpoint of securing the upper limit of the Young's modulus of the Al alloy film (200 GPa), The lower limit of the maximum particle size was set to 100 nm. A preferable maximum particle size is 130 nm or more and 320 nm or less.

  Here, the maximum grain size means the maximum value of the tangential diameter of crystal grains (also referred to as Feret diameter or Green diameter). Specifically, it is the distance (distance) between two parallel lines in a certain direction across the particle, and when there is a dent in the crystal grain, it is the distance between the parallel external tangents in the projection, and when there is no dent in the crystal grain ( (Sphere) is a value obtained by dividing the circumference by π.

  The Young's modulus and maximum particle size of the Al alloy film that characterize the present invention have been described above.

  The Al alloy film used in the present invention contains 0.05 to 5 atom% of rare earth elements, and the balance is Al and inevitable impurities. In the present invention, the composition of the Al alloy film to be used is not characterized, and the Al alloy film containing rare earth elements has heat resistance and is known to be used as a wiring material. From the viewpoint of providing a material suitable for the touch panel sensor, an Al alloy film in which the Young's modulus and the maximum particle size are controlled has not been disclosed so far. The lower limit of the rare earth element content is determined in order to effectively exhibit the heat resistance action, while the upper limit is to ensure the Young's modulus and the maximum particle size range defined in the present invention. It is determined. As the rare earth element content increases, the Young's modulus increases and the maximum particle size tends to decrease.

  As the rare earth element used in the present invention, an element obtained by adding Sc (scandium) and Y (yttrium) to a lanthanoid element (a total of 15 elements from La of atomic number 57 to Lu of atomic number 71 in the periodic table). Groups. In the present invention, these elements can be used alone or in combination of two or more. The rare earth element content is a single amount when contained alone, and when two or more kinds are contained, Total amount. Preferred rare earth elements are one or more elements selected from the group consisting of Nd, Gd, La, Y, Ce, Pr, and Dy.

  In the present invention, a wiring material in which a refractory metal film is laminated on the top and bottom of the Al alloy film is used. As described above, the refractory metal film is widely used as an underlayer of the Al alloy film in order to prevent the oxidation of Al. In the present invention, Mo, Ti, Cr, W, or an alloy thereof is used. Can do. The composition of the refractory metal films disposed above and below the Al alloy film may be the same or different at the top and bottom.

  The preferable thickness of the Al alloy film is about 150 to 600 nm, and the preferable thickness of the refractory metal film is about 30 to 150 nm.

  In the present invention, in order to obtain an Al alloy film whose Young's modulus and maximum particle size are appropriately controlled, in addition to using an Al alloy film containing a predetermined rare earth element, the conditions during sputtering are appropriately controlled. It is preferable. That is, in the present invention, it is recommended to form an Al alloy film by sputtering from the viewpoint of thinning and homogenizing the alloy components in the film and controlling the amount of added elements easily. It is preferable to control the film forming temperature to about 230 ° C. or lower and the Ar gas pressure to about 20 mTorr or lower. Moreover, it is preferable to control the substrate temperature at the time of sputtering to about 180 ° C. or lower. The higher the substrate temperature and the film formation temperature, the closer the film quality of the formed film becomes to that of the bulk, and a dense film tends to be formed, and the Young's modulus of the film tends to increase. Further, as the Ar gas pressure is increased, the density of the film decreases, and the Young's modulus of the film tends to decrease. Such adjustment of the film forming conditions is also preferable from the viewpoint of suppressing the sparseness of the film structure and easily causing corrosion.

In addition, it is preferable to heat-treat (anneal) the Al alloy film after forming into a film by sputtering method as mentioned above in the range of room temperature-230 degreeC. In the touch panel manufacturing process, a thermal history of about room temperature to about 250 ° C. is generally applied. However, when the annealing temperature increases, the Young's modulus decreases due to the precipitation of rare earth elements and the growth of Al alloy grains. The diameter increases . Specifically, an appropriate annealing temperature may be set in accordance with the amount of rare earth element added, but it is more preferably 150 to 230 ° C.

  In the present invention, there is a feature in the wiring composed of a laminated layer of an Al alloy film and a refractory metal film connected to the transparent conductive film, and the other configurations are not particularly limited, and a known configuration usually used in the field of touch panel sensors is used. Can be adopted.

  For example, a resistive film type touch panel sensor can be manufactured as follows. That is, after forming a transparent conductive film on a substrate, resist coating, exposure, development, and etching are sequentially performed, and then a refractory metal film, an Al alloy film, and a refractory metal film are sequentially formed, and resist coating, Exposure, development, and etching are performed to form a wiring, and then an insulating film or the like that covers the wiring is formed to form an upper electrode. Also, after forming a transparent conductive film on the substrate, photolithography is performed in the same manner as the upper electrode, and then the wiring made of a refractory metal film, an Al alloy film, and a refractory metal film, as in the case of the upper electrode. Then, an insulating film covering the wiring is formed, and a micro dot spacer is formed to form a lower electrode. Then, the touch panel sensor can be manufactured by laminating the upper electrode, the lower electrode, and the tail portion separately formed.

  The said transparent conductive film is not specifically limited, As a typical example, what consists of indium tin oxide (ITO) or indium zinc oxide (IZO) can be used. In addition, as the substrate (transparent substrate), for example, glass, polycarbonate, or polyamide can be used as a commonly used substrate. For example, the substrate of the lower electrode that is a fixed electrode is made of glass. And a polycarbonate film or the like can be used for the substrate of the upper electrode that needs flexibility.

  The touch panel sensor of the present invention can also be used as a touch panel sensor such as a capacitive method or an ultrasonic surface acoustic wave method in addition to the resistive film method.

  Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited by the following examples, and can be implemented with modifications within a range that can be adapted to the above and the following points, They are all included in the technical scope of the present invention.

Example 1
A non-alkali glass plate (plate thickness 0.7 mm, diameter 4 inches) is used as a substrate, and the surface of the substrate is subjected to DC magnetron sputtering, as shown in Table 1 below, and the type and content of rare earth elements (unit is atomic%) Then, Al alloy films (thicknesses are both about 500 nm) having different balances: Al and inevitable impurities were formed. Before film formation, the atmosphere in the chamber is once set to an ultimate vacuum of 3 × 10 ⁻⁶ Torr, and then a disk-type target having the same component composition as each Al alloy film and having a diameter of 4 inches is used. As shown in FIG. 1, the film formation temperature and the Ar gas pressure were varied. The sputtering conditions other than these are as follows. Next, the Al alloy after film formation was heat-treated at various annealing temperatures shown in Table 1 for 30 minutes in a nitrogen atmosphere. In Table 1, “-” means no heating (that is, room temperature). In addition, the composition of the formed Al alloy film was confirmed by inductively coupled plasma (ICP) mass spectrometry.
(Sputtering conditions)
Ar gas pressure: 2 mTorr
Ar gas flow rate: 30sccm
・ Sputtering power: 260W
・ Substrate temperature: Room temperature

  Using the Al alloy film obtained as described above, the hardness test of the film with a nanoindenter was performed, and the Young's modulus was measured. In this test, continuous stiffness measurement was performed using an XP chip using a Nano Indenter G200 (analysis software: Test Works 4) manufactured by Agilent Technologies. The indentation depth was 500 nm, and the average value of the results of measuring 15 points was determined.

  Further, the Al alloy film obtained as described above was observed with a TEM at a magnification of 150,000 times, and the grain size (constant tangent line) observed in the measurement field (one field is 1.2 μm × 1.6 μm). Diameter, Feret diameter). The measurement was performed in a total of three fields, and the maximum value in the three fields was taken as the maximum particle size.

  For a sample in which a pure Al film was formed instead of the Al alloy film, Young's modulus and maximum particle diameter were measured in the same manner as described above.

  These results are also shown in Table 1.

  In Table 1, No. 4 to 22 are examples of Al alloy films containing Nd as a rare earth element. When the sputtering conditions and the annealing temperature are all the same, the Young's modulus tends to increase as the amount of Nd increases [for example, when the annealing temperature is room temperature (−), No. 7, 10, 20], on the other hand, the maximum particle size tends to decrease slightly. Even if the Nd amount and the sputtering conditions are the same, if the annealing temperature increases beyond the preferable range of the present invention, the Young's modulus decreases and the maximum particle size increases [for example, No. 18 and 19], it can be seen that it is effective to control the upper limit of the annealing temperature to 230 ° C. in order to control the Young's modulus and the maximum grain size within the predetermined ranges.

  In Table 1, No. 23 to 40 are examples using an Al alloy film containing a rare earth element other than Nd. All of these were prepared by controlling the sputtering conditions and the annealing temperature within the preferred range of the present invention, including the rare earth element content defined in the present invention, so that the Young's modulus and the maximum particle size were within the scope of the present invention. Was controlled. Further, it has been confirmed by experiments that the same experimental results as those of Nd described above are observed when the rare earth elements other than Nd are used (not shown in Table 1).

  From these results, when the Al-rare earth element alloy film of the present invention is used, it is possible to provide a highly reliable touch panel sensor that has excellent durability in the lateral direction and is less likely to cause disconnection or increase in electrical resistance over time. Is highly expected.

  In contrast, no. Nos. 1 to 3 are examples of pure Al containing no rare earth element, and it was not possible to control the Young's modulus and maximum particle size defined in the present invention regardless of the annealing temperature.

Claims (5)

In the touch panel sensor having a transparent conductive film and a wiring connected to the transparent conductive film,
The wiring is composed of a refractory metal film, an Al alloy film, and a refractory metal film in order from the substrate side.
The Al alloy film contains 0.05 to 5 atomic% of a rare earth element, has a Young's modulus of 80 to 200 GPa, and the maximum value of the tangential diameter (Feret diameter) of crystal grains is 100 to 350 nm. Touch panel sensor characterized by this. 2. The Al alloy film is formed by performing sputtering at a room temperature to 230 ° C. after sputtering while controlling a film forming temperature during sputtering to 230 ° C. or less and an Ar gas pressure to 20 mTorr or less. The touch panel sensor described. The rare earth element, touch panel sensor according Nd, Gd, La, Y, Ce, to claim 1 or 2 is one or more elements selected from the group consisting of Pr and Dy. The transparent conductive film, a touch panel sensor according to any one of claims 1-3 made of indium tin oxide (ITO) or indium zinc oxide (IZO). It is a manufacturing method of the touch panel sensor in any one of Claims 1, 3, or 4,
A method for manufacturing a touch panel sensor, comprising sputtering at a deposition temperature of 230 ° C. or less and an Ar gas pressure of 20 mTorr or less during sputtering, and annealing at room temperature to 230 ° C. to form an Al alloy film.