Thin Film Sensor and Touch Display

Abstract

A thin film sensor and a touch display, the thin film sensor comprising a substrate, a metal nanowire layer and an optical adhesive layer. The metal nanowire layer is formed on the substrate and includes a plurality of electrode lines arranged at intervals. The optical adhesive layer is formed on the metal nanowire layer and matches the metal nanowire layer so that, under a weather resistance test at high temperature and high humidity (65°C / 90%RH / DC 5V / 240 hours), the change rate of the line resistance of the electrode lines is less than 10%, and the insulation impedance between two adjacent electrode lines is greater than 300 MΩ. Thereby, the reliability of the thin film sensor can be improved.

Description

Technical Field

[0001] The present invention relates to a thin film sensor and a touch display, and more particularly to a thin film sensor and a touch display containing metal nanowires. Background Art

[0002] In recent years, touch screens have been widely used in various electronic products. In particular, most mobile communication products use touch screens, and in order to facilitate portability, foldable touch screens have been further developed.

[0003] Generally, indium tin oxide (ITO for short) is used as the transparent conductive material for display panels. However, ITO thin films are easily broken and cannot be flexed, which is relatively limited in the application of portable electronic products. Therefore, the development of flexible transparent conductive films to replace ITO is one of the key projects in this technical field.

[0004] At present, one of the materials that have been relatively maturely developed to replace ITO is metal nanowires. A coating containing metal nanowires can be patterned to form conductive lines, and a thin film sensor can be further formed. However, in some use environments, the conductive lines of existing thin film sensors containing metal nanowires are prone to open circuit or short circuit, resulting in product malfunction. Therefore, providing a metal nanowire thin film sensor with improved reliability is the current research topic. Summary of the Invention

[0005] The present invention provides a thin film sensor capable of improving reliability.

[0006] In some embodiments of the thin film sensor of the present invention, it includes a substrate, a metal nanowire layer, and an optical adhesive layer. The metal nanowire layer is formed on the substrate and includes a plurality of electrode lines arranged at intervals. The optical adhesive layer is formed on the metal nanowire layer and matches the metal nanowire layer, so that under the weather resistance test at high temperature and high humidity (65°C / 90%RH / DC 5V / 240 hours), the line resistance change rate of the electrode lines is less than 10%, and the insulation impedance between two adjacent electrode lines is greater than 300 MΩ.

[0007] In some embodiments, the optical adhesive layer is selected from the following optical adhesive materials: non-ultraviolet-curable acrylic adhesive systems and rubber systems. Among them, the optical adhesive layer made of the non-ultraviolet-curable acrylic adhesive system material has a dielectric constant (frequency 100 KHz) less than 4, a water absorption rate (WA%) less than 0.3, and a water vapor transmission rate (38°C / 90%RH) less than 400 g / m 2 / day property; the optical adhesive layer made of the rubber-based material has a dielectric constant (frequency 100KHz) less than 4, a water absorption rate (WA%) less than 0.3, and a water vapor transmission rate (38°C / 90%RH) less than 100g / m 2 / day property.

[0008] In some embodiments, the thickness of the optical adhesive layer ranges from 25 to 250 microns.

[0009] In some embodiments, the metal nanowire layer further includes a plurality of insulating portions filled between the electrode lines.

[0010] In some embodiments, the metal nanowire layer is a structural layer in which the insulating portion is formed after the electrode lines are patterned.

[0011] In some embodiments, the thin film sensor further includes a protective layer formed on the metal nanowire layer, and the optical adhesive layer is formed on the protective layer.

[0012] In some embodiments, the protective layer has a dielectric constant (frequency 100KHz) less than 4 and a water vapor transmission rate (38°C / 90%RH) less than 12g / m 2 / day property.

[0013] In some embodiments, the thickness of the protective layer ranges from 0.2 to 10 microns.

[0014] In some embodiments, the line pitch between two adjacent electrode lines ranges from 10 to 50 microns.

[0015] In addition, the present invention provides a touch display including the aforementioned thin film sensor capable of improving reliability.

[0016] In some embodiments, the touch display of the present invention includes a display module and the aforementioned thin film sensor integrated into the display module.

[0017] In some embodiments, the touch display further includes an adhesive layer disposed between the display module and the thin film sensor, and the thin film sensor is attached to the display module through the adhesive layer.

[0018] In some embodiments, the thin film sensor is attached to the encapsulation substrate, polarizing plate, or electrode carrier substrate of the display module.

[0019] In some embodiments, the substrate is the substrate of the encapsulation substrate, polarizing plate, or electrode carrier substrate of the display module.

[0020] The present invention has at least the following effects: Through the design of the optical adhesive layer that matches the metal nanowire layer, the wire resistance change rate of the electrode wires in the metal nanowire layer is less than 10% under the weather resistance test at high temperature and high humidity (65 °C / 90% RH / DC 5V / 240 hours), and the insulation impedance between two adjacent electrode wires is greater than 300 MΩ, which can improve the reliability of the thin film sensor as a whole. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Other features and effects of the present invention will be clearly presented in the embodiments with reference to the drawings, where:

[0022] Figure 1 is a cross-sectional schematic view of an embodiment of the thin film sensor of the present invention; and

[0023] Figure 2 is a cross-sectional schematic view of an embodiment of the touch display device of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] Before the present invention is described in detail, it should be noted that in the following description, similar elements are denoted by the same reference numerals. The position terms such as "upper" and "lower" mentioned in the text only refer to the relative positions in the currently specified view, rather than absolute positions. In addition, unless otherwise specifically defined in the text, the state represented by the term "formed (or provided) on..." may include different states of direct formation and indirect formation.

[0025] Refer to Figure 1, is a cross-sectional schematic diagram of an embodiment of the thin film sensor of the present invention. The thin film sensor 1 includes: a substrate 11, a metal nanowire layer 12, and an optical adhesive layer 13. The metal nanowire layer 12 is formed on the substrate 11 and includes a plurality of electrode lines 121 arranged at intervals, where the line pitch between two adjacent electrode lines 121 is between about 10 micrometers and 50 micrometers. The optical adhesive layer 13 is formed on the metal nanowire layer 12 and is used to improve the reliability of the thin film sensor 1 in addition to providing a bonding function. More specifically, the optical adhesive layer 13 is matched with the metal nanowire layer 12 so that the resistance change rate of the electrode lines 121 is less than 10% under a weather resistance test of high temperature and high humidity (HTHH) (65 °C / 90% RH / DC 5V / 240 hours), and the insulation impedance between two adjacent electrode lines 121 is greater than 300 MΩ. Among them, since metal ions in the metal nanowire layer 12 will migrate, the optical adhesive layer 13 needs to be set in accordance with the metal nanowire layer 12 to effectively reduce the generation of metal ion migration. In contrast, for other sensors using traditional conductive material layers (such as ITO), since there is no problem of metal ion migration, there is no need and no special matching with the conductive material layer in the setting of the optical adhesive. In other words, the matching of the optical adhesive layer 13 with the metal nanowire layer 12 means that the properties of the optical adhesive selected for the optical adhesive layer 13 are coordinated with the metal nanowire material of the metal nanowire layer 12 to control the water content below the electrolysis critical value of metal ions, so as to effectively reduce the generation of metal ion migration.

[0026] In some embodiments, the thickness of the optical adhesive layer 13 can be between 25 and 250 micrometers, preferably between 50 and 150 micrometers. The material of the optical adhesive layer 13 can be selected from the following optical adhesive materials: non-ultraviolet curable acrylic adhesive systems and rubber systems. Among them, the optical adhesive layer 13 made of the non-ultraviolet curable acrylic adhesive system material has a dielectric constant (frequency 100 KHz) less than 4 (preferably less than 3), a water absorption rate (WA%) less than 0.3 (preferably less than 0.25), and a water vapor transmission rate (38 °C / 90% RH) less than 400 g / m 2 / day, that is, the water vapor transmission rate (WVTR) measured in an environment of 38 °C and 90% relative humidity is less than 400 grams per square meter per day (24 hours); the optical adhesive layer 13 made of the rubber system material has a dielectric constant (frequency 100 KHz) less than 4 (preferably less than 3), a water absorption rate (WA%) less than 0.3 (preferably less than 0.25), and a water vapor transmission rate (38 °C / 90% RH) less than 100 g / m 2 / day. In one embodiment, the optical adhesive layer 13 is preferably an optical adhesive made of a rubber system material.

[0027] In this embodiment, the metal nanowire layer 12 further includes an insulating portion 122 filled between the electrode lines 121. The manufacturing process of the metal nanowire layer 12 will be further described below.

[0028] In some embodiments, the metal nanowire layer 12 is formed by steps such as a coating step, a curing / drying step, and a patterning step using a dispersion or slurry containing metal nanowires. The coating step includes, for example but not limited to, processes such as screen printing, inkjet coating, and roll coating; in one embodiment, a roll-to-roll process can be used to coat a dispersion or slurry containing metal nanowires on the surface of a continuously supplied substrate. The dispersion containing metal nanowires can be a solvent such as water, alcohol, ketone, ether, hydrocarbon, or aromatic solvent (benzene, toluene, xylene, etc.); the above dispersion can also include additives, surfactants, or binders, such as carboxymethyl cellulose (CMC), 2-hydroxyethyl cellulose (HEC), hydroxypropylmethylcellulose (HPMC), sulfonate, sulfate, disulfonate, sulfosuccinate, phosphate, or fluorinated surfactant, etc. The metal nanowires layer can be composed of, for example, a silver nanowires layer, a gold nanowires layer, or a copper nanowires layer; more specifically, the "metal nanowires" used herein can be metal wires of elemental metals, metal wires of metal alloys, and combinations of the foregoing. The number of metal nanowires contained therein does not affect the scope of protection claimed in the present invention; and at least one cross-sectional dimension (i.e., the diameter of the cross-section) of a single metal nanowire is less than 500 nm, preferably less than 100 nm, and more preferably less than 50 nm; and the metal nanostructure referred to as "wire" in the present invention mainly has a high aspect ratio, for example, between 10 and 100,000. More specifically, the aspect ratio (length: diameter of the cross-section) of the metal nanowire can be greater than 10, preferably greater than 50, and more preferably greater than 100; the metal nanowire can be any metal, including (but not limited to) silver, gold, copper, nickel, and silver coated with gold. Other terms, such as silk, fiber, tube, etc., if they also have the above dimensions and high aspect ratio, are also within the scope covered by the present invention.

[0029] In some embodiments, the metal nanowires can be silver nanowires or silver nanofibers, which can have an average diameter of about 20 to 100 nanometers and an average length of about 20 to 100 micrometers. Preferably, they have an average diameter of about 20 to 70 nanometers and an average length of about 20 to 70 micrometers (i.e., an aspect ratio of 1000). In some embodiments, the diameter of the metal nanowires can be between 70 nanometers and 80 nanometers, and the length is about 8 micrometers.

[0030] The curing / drying step mainly allows substances such as solvents to be volatilized, so that the metal nanowires are distributed on the surface of the substrate in a random manner; preferably, the metal nanowires will adhere to the surface of the substrate without falling off to form the metal nanowire layer 12, and the metal nanowires can contact each other to provide a continuous current path, thereby forming a conductive network.

[0031] In addition, the aforementioned metal nanowires can be further post-treated to improve their conductivity. The post-treatment can be a process step including heating, plasma, corona discharge, UV ozone, or pressure. For example, after the step of curing to form the metal nanowire layer 12, pressure can be applied thereto using a roller. In one embodiment, a pressure of 50 to 3400 psi can be applied to the metal nanowire layer 12 through one or more rollers, preferably 100 to 1000 psi, 200 to 800 psi, or 300 to 500 psi. In some embodiments, the post-treatment of heating and pressure can be carried out simultaneously; specifically, the formed metal nanowires can be pressured through one or more rollers as described above and heated simultaneously. For example, the pressure applied by the roller is 10 to 500 psi, preferably 40 to 100 psi; at the same time, the roller is heated to between about 70 °C and 200 °C, preferably to between about 100 °C and 175 °C, which can improve the conductivity of the metal nanowire layer 12. In some embodiments, the metal nanowires can preferably be exposed to a reducing agent for post-treatment. For example, the metal nanowires containing silver nanowires can preferably be exposed to a silver reducing agent for post-treatment. The silver reducing agent includes borohydrides, such as sodium borohydride; boron-nitrogen compounds, such as dimethylamine borane (DMAB); or gas reducing agents, such as hydrogen (H2). The exposure time is about 10 seconds to about 30 minutes, preferably about 1 minute to about 10 minutes. And the above step of applying pressure can be implemented in an appropriate step according to actual needs.

[0032] The described patterning step can be carried out, for example, by exposure / development (i.e., the well-known lithography process) and etching on the cured metal nanowire layer 12. In one embodiment, the metal nanowire layer 12 preferably has the following characteristics: the light transmittance (Transmission) of visible light (e.g., with a wavelength between about 400 nm and 700 nm) can be greater than about 80%, and the surface resistance is between about 10 and 1000 ohms per square (sheet resistance, ohm / square); preferably, the light transmittance (Transmission) of the metal nanowire layer 12 for visible light (e.g., with a wavelength between about 400 nm and 700 nm) is greater than about 85%, and the surface resistance is between about 50 and 500 ohms per square (ohm / square).

[0033] In this embodiment, the insulating portion 122 of the metal nanowire layer 12 is an overcoat (OC) formed by coating a polymer between the electrode lines 121 and curing after the electrode lines 121 are patterned. By providing the insulating portion 122, the structural layer of the metal nanowire layer 12 can further maintain better electrical insulation between adjacent electrode lines 121. The material of the insulating portion 122 can be, for example: polymethyl methacrylate, polyvinyl alcohol, polyethylene terephthalate, polyethylene naphthalate, polycarbonate, polystyrene, polyvinyl toluene, polyvinyl xylene, polyimide, polyamide, polyamide-imide, polyetherimide, polysulfide, polysulfone, polyphenylene, polyphenylene ether, polyurethane, epoxy resin, polyurethane, polysilane, polysiloxane, poly(sil-acrylic), and so on.

[0034] In some embodiments, the material suitable for the substrate 11 is preferably a transparent material, which can be a flexible transparent substrate. The material can be selected from, for example: polyethylene terephthalate (PET), polyimide (PI), polycarbonate (PC), polymethyl methacrylate (PMMA), polyvinyl chloride (PVC), polypropylene (PP), polyethylene naphthalate (PEN), polystyrene (PS), cyclo-olefin polymers (COP), and so on.

[0035] In this embodiment, the thin film sensor 1 further includes a passivation layer 14 formed between the metal nanowire layer 12 and the optical adhesive layer 13. Specifically, the passivation layer 14 can be formed on the surface of the metal nanowire layer 12, and then the optical adhesive layer 13 is formed on the surface of the passivation layer 14, such that the passivation layer 14 is in direct contact with the metal nanowire layer 12 and the optical adhesive layer 13 respectively. In another embodiment, an optical layer, a functional layer or other laminated layers required by the design can be further provided between the passivation layer 14 and the metal nanowire layer 12 or between the passivation layer 14 and the optical adhesive layer 13, which is not limited by this disclosure. In addition, the passivation layer 14 has the following properties: the dielectric constant (frequency 100KHz) is less than 4 (preferably less than 3), that is, the dielectric constant measured at a frequency of 100KHz is less than 4, and the water vapor transmission rate (38℃ / 90%RH) is less than 12g / m 2 / day. The thickness of the passivation layer 14 can range from 0.2 to 10 microns, preferably from 2.5 to 6.5 microns. Suitable materials for the passivation layer 14 can be, for example, dry film, photoresist, ink, etc. Among them, in one embodiment, the ink can be, for example, a baking type insulating ink and the baking temperature of the insulating ink is less than 110℃, which is not limited by this disclosure. Through the design of the passivation layer 14, water vapor can be further blocked to improve the reliability of the thin film sensor 1 in a high temperature and high humidity environment.

[0036] The completed samples were tested by applying a direct current of 5V in a high temperature and high humidity environment of 65℃ and 90% relative humidity. The test results are summarized in Table 1 below, where:

[0037] Experimental Example 1 used Figure 1 In the structure of the embodiment, the structure without the passivation layer 14 was used as the sample;

[0038] Experimental Example 2 used Figure 1 In the structure of the embodiment, the structure including the optical adhesive layer 13 and the passivation layer 14 was used as the sample;

[0039] Comparative Example 1 used Figure 1 In the structure of the embodiment, the structure without the passivation layer 14 and the optical adhesive layer 13 was used as the sample;

[0040] Comparative Example 2 used Figure 1 In the structure of the embodiment, the structure without the optical adhesive layer 13 was used as the sample.

[0041] Table 1

[0042] Test Time (hours) Electrical Results Experimental Example 1 240 Normal Experimental Example 2 500 Normal Comparative Example 1 12 Failed Comparative Example 2 72 Failed

[0043] As can be seen from the test results shown in Table 1, for Samples of Experimental Examples 1 and 2 with the optical adhesive layer 13 compared to Samples of Comparative Examples 1 and 2 without the optical adhesive layer, the reliability of Experimental Examples 1 and 2 is significantly better than that of Comparative Examples 1 and 2 in a high-temperature and high-humidity environment. That is to say, the verification result shows that the thin-film sensor 1 of the present disclosure can effectively improve reliability through the design of the optical adhesive layer 13. Further, it can be seen from Experimental Example 2 that if the laminated structure design of the optical adhesive layer 13 and the protective layer 14 is adopted in the thin-film sensor 1, the reliability can be further greatly improved.

[0044] Please refer to Figure 2 , which is a schematic cross-sectional view of an embodiment of the touch display of the present invention. The touch display 100 of this embodiment includes a thin-film sensor 1, a display module 2, and an adhesive layer 3. The thin-film sensor 1 can adopt, for example, Figure 1 the structure of the thin-film sensor 1 disclosed in the embodiment of

[0045] , and the related structure and material content will not be elaborated here. The display module 2 can be, for example, an organic light-emitting diode display module (OLED), a liquid crystal display module (LCD), etc. In addition, since the thin-film sensor 1 of this embodiment uses a metal nanowire layer 12 with better flexibility as the touch electrode, in order to make the touch display 100 achieve a bendable effect, the display module 2 can also be a flexible display module. The adhesive layer 3 is disposed between the thin-film sensor 1 and the display module 2.

[0046] In summary, through the design of the optical adhesive layer 13 that matches the metal nanowire layer 12 of the thin-film sensor 1 of the present invention, under the weather resistance test of high temperature and high humidity (65°C / 90% RH / DC 5V / 240 hours), the line resistance change rate of the electrode line 121 is less than 10%, and the insulation impedance between two adjacent electrode lines 121 is greater than 300 MΩ, which can overall improve the reliability of the thin-film sensor 1.

[0047] The above are only the embodiments of the present invention, and the scope of implementation of the present invention cannot be limited thereby. That is, all simple equivalent changes and modifications made according to the claims and the content of the specification of the present invention still fall within the scope of the present invention.

Claims

1. A thin film sensor, characterized in that: Comprising: a substrate; a metal nanowire layer formed on the substrate and including a plurality of electrode lines arranged at intervals; and an optical adhesive layer formed on the metal nanowire layer and matching the metal nanowire layer, at a temperature of 65 °C, a relative humidity of 90%, 5 V direct current, and for 240 hours, so that under the weather resistance test of high temperature and high humidity, the line resistance change rate of the electrode lines is less than 10%, and the insulation impedance between two adjacent electrode lines is greater than 300 MΩ; The optical adhesive layer is selected from the following optical adhesive materials: non-UV-curable acrylic adhesive systems and rubber systems. The optical adhesive layer made of the non-UV-curable acrylic adhesive system material has a dielectric constant less than 4 at a frequency of 100 KHz, a water absorption rate less than 0.3, and a water vapor transmission rate less than 400 g / m 2 / day at a temperature of 38 °C and a relative humidity of 90%. The optical adhesive layer made of the rubber system material has a dielectric constant less than 4 at a frequency of 100 KHz, a water absorption rate less than 0.3, and a water vapor transmission rate less than 100 g / m 2 / day at a temperature of 38 °C and a relative humidity of 90%.

2. The thin film sensor according to claim 1, wherein: The thickness of the optical adhesive layer ranges from 25 to 250 microns.

3. The thin film sensor according to claim 1, wherein: The metal nanowire layer further includes a plurality of insulating portions filled between the electrode lines.

4. The thin film sensor according to claim 3, characterized in that: The metal nanowire layer is a structural layer in which the insulating portions are formed after the electrode lines are patterned.

5. The thin film sensor according to claim 1, characterized in that: It further includes a protective layer formed on the metal nanowire layer, and the optical adhesive layer is formed on the protective layer.

6. The thin film sensor according to claim 5, wherein: The protective layer has a dielectric constant of less than 4 at a frequency of 100 KHz and a water vapor transmission rate of less than 12 g / m 2 / day at a temperature of 38 °C and a relative humidity of 90%.

7. The thin film sensor according to claim 5, characterized in that: The thickness of the protective layer ranges from 0.2 to 10 microns.

8. The thin film sensor according to claim 1, wherein: The line pitch between two adjacent electrode lines ranges from 10 to 50 microns.

9. A touch display, characterized in that: Comprising: a display module; and the thin film sensor according to any one of claims 1 to 8, integrated into the display module.

10. The touch display according to claim 9, wherein: It further includes an adhesive layer disposed between the display module and the thin film sensor, and the thin film sensor is attached to the display module through the adhesive layer.

11. The touch display according to claim 10, wherein: The thin film sensor is attached to the encapsulation substrate, polarizing plate or electrode carrier substrate of the display module.

12. The touch display according to claim 9, wherein: The substrate is the substrate of the encapsulation substrate, polarizing plate or electrode carrier substrate of the display module.

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