A visual humidity sensor based on AC electroluminescence and its preparation method

Abstract

The present invention relates to the technical field of humidity sensors and discloses a visual humidity sensor based on alternating current electroluminescence. The sensor comprises a base layer and a humidity-sensitive luminescent layer, wherein a coplanar double electrode layer is provided between the base layer and the humidity-sensitive luminescent layer, and the humidity-sensitive luminescent layer is coated on the surface of the coplanar double electrode layer. The two electrodes of the coplanar double electrode layer are located in the same plane and are closely adjacent to each other. The two electrodes of the coplanar double electrode layer have a thickness of 20nm-20μm and are made of any one or more combinations of metals, transparent conductive oxides, nano-conductive materials, ion-conductive gels, and conductive polymer materials. The humidity sensor senses humidity by changing the luminous intensity caused by changes in capacitance and impedance before and after moisture absorption. The luminous intensity changes before and after moisture absorption, and the luminous brightness decreases with increasing humidity.

Description

Technical Field

[0001] The present invention relates to the technical field of humidity sensors, in particular to a visual humidity sensor based on alternating current electroluminescence and a preparation method thereof. Background Art

[0002] A humidity sensor is a device that can sense and measure the ambient humidity level and convert it into a measurable signal. It can generally be divided into: resistive humidity sensor, capacitive humidity sensor, thermistor humidity sensor, dew point humidity sensor, optical humidity sensor, semiconductor humidity sensor, electrochemical humidity sensor, etc.

[0003] Traditional humidity sensor devices use a sandwich electrode structure, which is not conducive to the penetration of water vapor. At the same time, during repeated charging and discharging, the sandwich electrode plate may suffer from reduced cycle stability due to problems such as interface stress and material expansion. Some active materials change significantly in volume during charging and discharging, and the volume effect of the active material may cause damage to the electrode structure. Therefore, a visual humidity sensor based on AC electroluminescence and its preparation method are proposed to solve the above problems. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the present invention provides a visual humidity sensor based on AC electroluminescence and a preparation method thereof, which has the advantages of easy production, simple structure, high sensitivity, etc., and solves the problems mentioned in the above background technology.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution: a visual humidity sensor based on AC electroluminescence, comprising a base layer and a humidity-sensitive luminescent layer, a coplanar double electrode layer is arranged between the base layer and the humidity-sensitive luminescent layer, and the humidity-sensitive luminescent layer is coated on the surface of the coplanar double electrode layer.

[0006] Preferably, the two electrodes of the coplanar double electrode layer are in the same plane, the electrode spacing is 50 μm-2 mm, and the thickness of the two electrodes of the coplanar double electrode layer is 20 nm-20 μm.

[0007] Preferably, the two electrodes of the coplanar double electrode layer are made of any one or more combinations of metals, transparent conductive oxides, nano-conductive materials, ion-conductive gels and conductive polymer materials.

[0008] Preferably, the humidity-sensitive luminescent layer is formed by uniformly mixing and solidifying a luminescent material and a hydrogel, and the thickness of the humidity-sensitive luminescent layer is 10 μm-200 μm.

[0009] Preferably, the luminescent material is AC electroluminescent phosphor, SrAl2O4 luminescent material, Eu 2+Luminescent materials and any one or more combinations of various zinc sulfide-doped luminescent materials.

[0010] Preferably, the hydrogel is a humidity-sensitive hydrogel, including any one or more combinations of polyvinyl alcohol, polyacrylamide, sodium polyacrylate, acrylate polymer, and cellulose hydrogel.

[0011] Preferably, the specific steps are:

[0012] S1: Select a base layer of appropriate size and use a suitable process to coat copper on the surface of the base layer to form a coplanar double electrode layer;

[0013] S2: mixing the luminescent material and the hydrogel in a certain weight ratio;

[0014] S3: uniformly coating the mixed material on the coplanar double electrode layer to form a humidity-sensitive light-emitting layer;

[0015] S4: Place the humidity sensor on a hot plate at 60-120°C and cure for 15 minutes to 3 hours.

[0016] S5: Solder copper wires to the two electrodes of the coplanar double-electrode layer respectively and connect them to the output end of the AC high-voltage power driver.

[0017] Preferably, the ratio of the luminescent material to the hydrogel is 7:3.

[0018] Preferably, the optimal temperature of the hot stage is 80° C., and the optimal curing time is 1 hour.

[0019] Compared with the prior art, the present invention provides a visual humidity sensor based on AC electroluminescence and a preparation method thereof, which has the following beneficial effects:

[0020] 1. This visual humidity sensor based on AC electroluminescence senses humidity by changing the luminous intensity caused by changes in capacitance and impedance before and after moisture absorption. The luminous intensity changes before and after moisture absorption, and the luminous brightness decreases as the humidity increases.

[0021] 2. This visual humidity sensor based on AC electroluminescence adopts a coplanar dual-electrode structure, which makes full contact between the humidity-sensitive luminescent layer and the air. At the same time, it takes advantage of the strong hygroscopicity of hydrogel, and has high humidity sensing sensitivity. The hydrogel and electroluminescent material are compounded into a humidity-sensitive luminescent layer, which has the characteristics of simple process. When the hydrogel absorbs water and expands, the capacitance increases, the resistance decreases, and the luminescence brightness decreases. Compared with existing humidity sensors, it is based on a different visual humidity sensing mechanism and presents a different luminescence effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1This is a schematic diagram of the structure of a visual humidity sensor based on AC electroluminescence proposed by the present invention;

[0023] Figure 2 This is a luminescence spectrum diagram of a visualized humidity sensor based on AC electroluminescence proposed by the present invention;

[0024] Figure 3 This is a schematic diagram of a humidity sensor with a printed circuit board as a substrate in Example 1 of the present invention;

[0025] Figure 4 Schematic diagram of the spiral coplanar dual-electrode structure in Example 3 of the present invention;

[0026] Figure 5 This is a schematic diagram of the humidity sensor in Example 3 of the present invention emitting light after being powered on.

[0027] In the figure: 1 base layer, 2 coplanar double electrode layer, 3 humidity-sensitive light-emitting layer. DETAILED DESCRIPTION

[0028] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0029] Example 1: Please refer to Figure 1-3 A visual humidity sensor based on AC electroluminescence includes a base layer 1 and a humidity-sensitive luminescent layer 3, a coplanar double electrode layer 2 is arranged between the base layer 1 and the humidity-sensitive luminescent layer 3, and the humidity-sensitive luminescent layer 3 is coated on the surface of the coplanar double electrode layer 2.

[0030] The two electrodes of the coplanar double electrode layer 2 are in the same plane, the electrode spacing is 50 μm-2 mm, and the thickness of the two electrodes of the coplanar double electrode layer 2 is 20 nm-20 μm.

[0031] The two electrodes of the coplanar double electrode layer 2 are made of any one of metal, transparent conductive oxide, nano-conductive material, ion conductive gel and conductive polymer material.

[0032] The humidity-sensitive luminescent layer 3 is formed by uniformly mixing and solidifying a luminescent material and a hydrogel. The thickness of the humidity-sensitive luminescent layer 3 is 10 μm-200 μm.

[0033] The luminescent materials are AC electroluminescent phosphor, SrAl2O4 luminescent material, Eu 2+ Any one of the luminescent materials and various zinc sulfide-doped luminescent materials.

[0034] The hydrogel is a humidity-sensitive hydrogel, including any one of polyvinyl alcohol, polyacrylamide, sodium polyacrylate, acrylate polymer, and cellulose hydrogel.

[0035] A method for preparing a visual humidity sensor based on AC electroluminescence, comprising the following steps:

[0036] S1: A printed circuit board with a size of 6 cm × 3 cm × 1 mm is selected as the base layer 1. A copper layer with a thickness of 35 μm is prepared by a copper plating process to form a coplanar double electrode layer 2 on the surface of the base layer 1;

[0037] S2: mixing the luminescent material and the hydrogel in a weight ratio of 7:3, wherein the luminescent material is zinc sulfide-doped copper phosphor;

[0038] S3: The mixed material is evenly coated on the coplanar double electrode layer 2 to form a humidity-sensitive light-emitting layer 3 with a thickness of 40 μm;

[0039] S4: Place the humidity sensor on a hot plate at 80°C and cure for 1 hour.

[0040] S5: Solder copper wires to the two electrodes of the coplanar double-electrode layer 2 respectively, and connect them to the output end of the AC high-voltage power driver.

[0041] When the AC high-voltage power supply is turned on, the humidity-sensitive light-emitting layer 3 between the coplanar double electrodes emits visible light. As the ambient humidity changes, the capacitance of the humidity-sensitive light-emitting layer 3 changes, and the brightness of the emitted light changes simultaneously.

[0042] Humidity sensing process:

[0043] When the humidity is 15%, the luminous brightness is high; when the humidity gradually increases, the luminous brightness gradually decreases; when the humidity decreases again, the luminous brightness gradually increases again. Use the fiber optic spectrometer to focus on the luminous area and measure the spectrum. Figure 2 As shown, the emission peak is located at 477 nm, which is in the visible blue light region.

[0044] In summary, this visual humidity sensor based on AC electroluminescence senses humidity by changing the luminous intensity caused by changes in capacitance and impedance before and after moisture absorption. The luminous intensity changes before and after moisture absorption, and the luminous brightness decreases as the humidity increases.

[0045] Moreover, by adopting a coplanar dual-electrode structure, the humidity-sensitive luminescent layer 3 is in full contact with the air, and the strong hygroscopicity of the hydrogel is utilized, so the humidity sensing sensitivity is high. The hydrogel and the electroluminescent material are compounded into the humidity-sensitive luminescent layer 3, which has the characteristics of simple process. When the hydrogel absorbs water and expands, the capacitance increases, the resistance decreases, and the luminous brightness decreases. Compared with the existing humidity sensors, it is based on a different visual humidity sensing mechanism and presents a different luminous effect.

[0046] Example 2: Please refer to Figure 1-2 , a preparation method of a visual humidity sensor based on AC electroluminescence, the specific steps are as follows:

[0047] S1: A quartz glass plate with dimensions of 15 mm × 20 mm × 1.1 mm was selected as the base layer 1. A transparent interdigitated ITO double electrode layer with a thickness of 200 nm was prepared by magnetron sputtering to form a coplanar double electrode layer 2 with a line width of 80 μm, a finger length of 8.5 mm, and 30 interdigit pairs.

[0048] S2: mixing the luminescent material and the hydrogel in a weight ratio of 7:3, wherein the luminescent material is zinc sulfide-doped copper phosphor;

[0049] S3: The mixed material is evenly coated on the coplanar double electrode layer 2 to form a humidity-sensitive light-emitting layer 3 with a thickness of 40 μm;

[0050] S4: Place the humidity sensor on a hot plate at 80°C and cure for 1 hour.

[0051] S5: Solder copper wires to the two electrodes of the coplanar double-electrode layer 2 respectively, and connect them to the output end of the AC high-voltage power driver.

[0052] After connecting to a 200V, 1kHz AC power supply, luminescence can be observed. When the humidity changes, the luminescence intensity changes. When the humidity increases, the luminescence intensity decreases, and when the humidity decreases, the luminescence intensity increases.

[0053] In summary, this visual humidity sensor based on AC electroluminescence senses humidity by changing the luminous intensity caused by changes in capacitance and impedance before and after moisture absorption. The luminous intensity changes before and after moisture absorption, and the luminous brightness decreases as the humidity increases.

[0054] Moreover, by adopting a coplanar dual-electrode structure, the humidity-sensitive luminescent layer 3 is in full contact with the air, and the strong hygroscopicity of the hydrogel is utilized, so the humidity sensing sensitivity is high. The hydrogel and the electroluminescent material are compounded into the humidity-sensitive luminescent layer 3, which has the characteristics of simple process. When the hydrogel absorbs water and expands, the capacitance increases, the resistance decreases, and the luminous brightness decreases. Compared with the existing humidity sensors, it is based on a different visual humidity sensing mechanism and presents a different luminous effect.

[0055] Example 3: Please refer to Figure 1 、 2 , 4 and 5, a method for preparing a visual humidity sensor based on AC electroluminescence, the specific steps are:

[0056] S1: Select a polyimide substrate 1 with a size of 11.6 mm × 16.2 mm × 1 mm, and prepare a metal electrode layer with a thickness of 13 μm by using the copper plating process of a printed circuit board. The metal can be Cu, Au, or Ni, forming a coplanar double electrode layer 2 with a line width of 100 μm and a line spacing of 100 μm.

[0057] S2: mixing the luminescent material and the hydrogel in a weight ratio of 7:3, wherein the luminescent material is zinc sulfide-doped copper phosphor;

[0058] S3: The mixed material is evenly coated on the coplanar double electrode layer 2 to form a humidity-sensitive light-emitting layer 3 with a thickness of 40 μm;

[0059] S4: Place the humidity sensor on a hot plate at 80°C and cure for 1 hour.

[0060] S5: Solder copper wires to the two electrodes of the coplanar double-electrode layer 2 respectively, and connect them to the output end of the AC high-voltage power driver.

[0061] After connecting to a 200V, 1kHz AC power supply, luminescence can be observed. When the humidity changes, the luminescence intensity changes. When the humidity increases, the luminescence intensity decreases, and when the humidity decreases, the luminescence intensity increases.

[0062] In summary, this visual humidity sensor based on AC electroluminescence senses humidity by changing the capacitance and impedance before and after moisture absorption, causing changes in luminous intensity. The luminous intensity changes before and after moisture absorption, and the luminous brightness decreases with increasing humidity.

[0063] Moreover, by adopting a coplanar dual-electrode structure, the humidity-sensitive luminescent layer 3 is in full contact with the air, and the strong hygroscopicity of the hydrogel is utilized, so the humidity sensing sensitivity is high. The hydrogel and the electroluminescent material are compounded into the humidity-sensitive luminescent layer 3, which has the characteristics of simple process. When the hydrogel absorbs water and expands, the capacitance increases, the resistance decreases, and the luminous brightness decreases. Compared with the existing humidity sensors, it is based on a different visual humidity sensing mechanism and presents a different luminous effect.

[0064] It should be noted that the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or apparatus that includes a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprises a ..." does not preclude the presence of other identical elements in the process, method, article, or apparatus that includes the element.

[0065] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A visual humidity sensor based on AC electroluminescence, characterized by: It comprises a base layer (1) and a humidity-sensitive luminescent layer (3), wherein a coplanar double electrode layer (2) is provided between the base layer (1) and the humidity-sensitive luminescent layer (3), and the humidity-sensitive luminescent layer (3) is coated on the surface of the coplanar double electrode layer (2); The two electrodes of the coplanar double electrode layer (2) are located in the same plane, the electrode spacing is 50 μm-2 mm, and the thickness of the two electrodes of the coplanar double electrode layer (2) is 20 nm-20 μm; The humidity-sensitive luminescent layer (3) is formed by uniformly mixing and solidifying a luminescent material and a hydrogel, and the thickness of the humidity-sensitive luminescent layer (3) is 10 μm-200 μm.

2. The AC electroluminescence-based visual humidity sensor according to claim 1, characterized in that: The two electrodes of the coplanar double electrode layer (2) are made of any one or more combinations of metals, transparent conductive oxides, nano-conductive materials, ion-conductive gels and conductive polymer materials.

3. The AC electroluminescence-based visual humidity sensor according to claim 1, characterized in that: The luminescent material is AC electroluminescent phosphor.

4. The AC electroluminescence-based visual humidity sensor according to claim 1, characterized in that: The luminescent material is SrAl2O4 luminescent material.

5. The AC electroluminescence-based visual humidity sensor according to claim 1, characterized in that: The luminescent material is Eu 2+ Luminescent materials.

6. The AC electroluminescence-based visual humidity sensor according to claim 1, characterized in that: The luminescent material is zinc sulfide-doped luminescent material.

7. The AC electroluminescence-based visual humidity sensor according to claim 1, characterized in that: The hydrogel is a humidity-sensitive hydrogel, comprising any one or more combinations of polyvinyl alcohol, polyacrylamide, sodium polyacrylate, acrylate polymer, and cellulose hydrogel.

8. The method for preparing a visual humidity sensor based on AC electroluminescence according to any one of claims 1 to 7, characterized in that: The specific steps are: S1: Select a base layer (1) of appropriate size, and use a suitable process to coat copper on the surface of the base layer (1) to form a coplanar double electrode layer (2); S2: mixing the luminescent material and the hydrogel in a certain weight ratio; S3: uniformly coating the mixed material on the coplanar double electrode layer (2) to form a humidity-sensitive light-emitting layer (3); S4: Place the humidity sensor on a hot plate at 60-120°C and cure for 15 minutes to 3 hours. S5: Weld copper wires onto the two electrodes of the coplanar double electrode layer (2) and connect them to the output end of the AC high voltage power driver.

9. The method for preparing a visual humidity sensor based on AC electroluminescence according to claim 8, characterized in that The optimal ratio of the luminescent material to the hydrogel is 7:

3.

10. The method for preparing a visual humidity sensor based on AC electroluminescence according to claim 8, characterized in that The optimal temperature of the hot stage is 80°C, and the optimal curing time is 1 hour.

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