Ultrasonic fingerprint module and manufacturing method thereof and electronic device

Abstract

The present invention discloses an ultrasonic fingerprint module, a manufacturing method thereof and an electronic device, wherein the ultrasonic fingerprint module comprises an ultrasonic detection layer and an ink layer, wherein the ultrasonic detection layer has an ultrasonic receiving surface, the ink layer is arranged on a side of the ultrasonic detection layer away from the ultrasonic receiving surface, and the ink layer is used to reflect the ultrasonic wave emitted from the ultrasonic detection layer, and the ink layer contains a resin material and carbon powder particles, wherein the average particle size of the carbon powder particles is 0.5 microns to 5 microns, and the mass proportion of the carbon powder particles is 2.5% to 15%. The ink layer can be used to reflect the ultrasonic wave emitted from the ultrasonic detection layer toward the fingerprint to be detected, so that the ultrasonic signal received by the fingerprint to be detected is strengthened, the ultrasonic signal intensity emitted by the ultrasonic fingerprint module toward the fingerprint to be detected is increased, and the fingerprint recognition efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of fingerprint recognition, and in particular to an ultrasonic fingerprint module, a manufacturing method thereof, and an electronic device. Background Art

[0002] Currently, ultrasonic fingerprint modules identify user fingerprints by comparing the ultrasonic signals reflected from the valley area of ​​the user's fingerprint with the ultrasonic signals reflected from the ridge area of ​​the user's fingerprint. However, since ultrasonic fingerprint modules are easily permeable to ultrasonic signals, the strength of the ultrasonic signals obtained by the ultrasonic fingerprint module is reduced, and it is difficult to distinguish the difference between the ultrasonic signals in the valley area and the ultrasonic signals in the ridge area, which reduces the efficiency of fingerprint recognition. Summary of the invention

[0003] The purpose of the present application is to provide an ultrasonic fingerprint module and a manufacturing method and electronic device for improving fingerprint recognition efficiency.

[0004] The present application provides an ultrasonic fingerprint module, wherein the ultrasonic fingerprint module comprises an ultrasonic detection layer and an ink layer, the ultrasonic detection layer having an ultrasonic receiving surface, the ink layer being arranged on a side of the ultrasonic detection layer away from the ultrasonic receiving surface, the ink layer being used to reflect ultrasonic waves emitted from the ultrasonic detection layer, the ink layer containing carbon powder particles, the average particle size of the carbon powder particles being 0.5 microns to 5 microns, and the mass proportion of the carbon powder particles being 2.5% to 15%; the ink layer can be used to reflect the ultrasonic waves emitted from the ultrasonic detection layer toward a fingerprint to be detected, so that the ultrasonic signal received by the fingerprint to be detected is enhanced, and the average particle size of the carbon powder particles in the ink layer is set to 0.5 microns to 5 microns, and the mass proportion of the carbon powder particles is 2.5% to 15%, so that the surface roughness of the ink layer can be effectively reduced, and the reflection uniformity of the ink layer to the ultrasonic signal is enhanced, so that the ultrasonic fingerprint module can obtain a clearer fingerprint image.

[0005] The average particle size of the carbon powder particles is 0.8 micrometers to 2 micrometers, and further 1.0 micrometers, so that the roughness of the ink layer can be further reduced.

[0006] The carbon powder particles account for 3.0% to 10% of the ink layer by mass, so that the roughness of the ink layer can be further reduced.

[0007] The carbon powder particles account for 5% of the mass of the ink layer, which ensures that the roughness of the ink layer is reduced and reduces the production cost of the ink layer.

[0008] The ink layer contains resin material to ensure that the ink layer can provide insulation and protection for the ultrasonic detection layer, and the cured resin material has an elastic modulus similar to that of the plastic sheet to ensure that the ink layer has approximately the same ultrasonic reflection efficiency as that of the plastic sheet.

[0009] The resin material includes any one of acrylic resin, polyester resin, isocyanate resin, phenolic resin, epoxy resin or a combination of multiple resin materials, so that the material selection of the ink layer can be diversified.

[0010] Among them, the resin material is epoxy resin with CAS number 38891-59-7, which further improves the fingerprint recognition accuracy of the ultrasonic fingerprint module.

[0011] Among them, the ink layer is provided with a leveling agent, and the leveling agent is used to improve the surface leveling of the ink layer during the production process, and to improve the surface leveling of the ink layer finally formed. The leveling agent is used to defoam the surface of the ink layer, control the surface flatness of the ink layer, and improve the surface leveling performance of the ink layer, so that the surface roughness of the ink layer is effectively reduced.

[0012] Among them, the ink layer is provided with a defoaming agent, and the defoaming agent is used to eliminate bubbles in the ink layer during the production process and eliminate bubbles in the ink layer finally formed. The defoaming agent can eliminate the performance of the ink layer generating bubbles during the preparation process, so that the number of bubbles in the ink layer is reduced, which can improve the clarity of the fingerprint image obtained by the ultrasonic fingerprint module.

[0013] Among them, the ultrasonic detection layer includes a substrate layer, a pixel electrode layer, a piezoelectric layer and a conductive electrode stacked in sequence, and the ink layer is arranged on the side of the conductive electrode away from the piezoelectric layer, so that the ultrasonic fingerprint module is thinner and convenient for the ultrasonic fingerprint module to be integrated into the display screen of an electronic device.

[0014] The thickness of the ink layer is 5 micrometers to 30 micrometers, so that the surface roughness of the ink layer is effectively reduced, and the clarity of the fingerprint image obtained by the ultrasonic fingerprint module is effectively improved.

[0015] The thickness of the ink layer is 20 micrometers to 30 micrometers, so that the surface roughness of the ink layer is further reduced and the clarity of the fingerprint image obtained by the ultrasonic fingerprint module is further improved.

[0016] The thickness of the ink layer is 25 micrometers, so that the surface roughness of the ink layer is further reduced, and the SNR value and LPMM value of the ultrasonic fingerprint module are more excellent.

[0017] The present application also provides a method for manufacturing an ultrasonic fingerprint module, wherein the method for manufacturing an ultrasonic fingerprint module comprises the steps of:

[0018] Providing an ultrasonic detection layer, the ultrasonic detection layer having an ultrasonic receiving surface and a detection layer bottom surface disposed opposite to the ultrasonic receiving surface;

[0019] Providing a liquid ink material containing carbon powder particles, wherein the average particle size of the carbon powder particles is 0.5 micrometers to 5 micrometers, and the mass proportion of the carbon powder particles is 2.5% to 15%;

[0020] The liquid ink material is spread on the bottom surface of the detection layer, and an ink layer is formed after the liquid ink material is solidified. The ink layer covers the ultrasonic receiving surface of the ultrasonic detection layer. The liquid ink material is spread on the bottom surface of the detection layer to facilitate the formation of a large area of ​​the ink layer, thereby obtaining a large area of ​​the ultrasonic fingerprint module, thereby increasing the fingerprint recognition area of ​​the ultrasonic fingerprint module.

[0021] Among them, the liquid ink material also contains resin material, leveling agent and defoaming agent. The resin material, carbon powder particles, leveling agent and defoaming agent are mixed and stirred to form the liquid ink material, so that the surface roughness of the ink layer is reduced, and the ink layer is free of bubbles, thereby improving the reflection uniformity of the ink layer to the ultrasonic signal, thereby improving the fingerprint recognition efficiency of the ultrasonic fingerprint module.

[0022] Among them, in the step of providing an ultrasonic detection layer, a substrate layer, a pixel electrode, a piezoelectric layer and a conductive electrode are sequentially formed and stacked, and the bottom surface of the detection layer is formed on a side of the conductive electrode away from the piezoelectric layer, so that the ultrasonic fingerprint module is thinner and convenient for the integration of the ultrasonic fingerprint module into the display screen of an electronic device.

[0023] The present application also provides an electronic device, wherein the electronic device includes the above-mentioned ultrasonic fingerprint module, so that the electronic device can meet diversified fingerprint recognition requirements and improve fingerprint recognition efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solution of the present invention, the drawings required for use in the implementation mode will be briefly introduced below. Obviously, the drawings described below are only some implementation modes of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0025] Figure 1 is a schematic diagram of an ultrasonic fingerprint module provided in an embodiment of the present application;

[0026] Figure 2 is another schematic diagram of the ultrasonic fingerprint module provided in an embodiment of the present application;

[0027] Figure 3 is another schematic diagram of the ultrasonic fingerprint module provided in an embodiment of the present application;

[0028] Figure 4 It is a flow chart of a method for manufacturing an ultrasonic fingerprint module provided in an embodiment of the present application;

[0029] Figure 5 is a schematic diagram of a display screen assembly provided in an embodiment of the present application;

[0030] Figure 6 is another schematic diagram of a display screen assembly provided in an embodiment of the present application;

[0031] Figure 7 is a schematic diagram of a display screen assembly provided by another embodiment of the present application;

[0032] Figure 8 is another schematic diagram of a display screen assembly provided by another embodiment of the present application;

[0033] Fig. 9 is a schematic diagram of a display screen assembly provided by another embodiment of the present application;

[0034] Fig.10 is a schematic diagram of a display screen assembly provided by another embodiment of the present application;

[0035] Fig.11 It is a cross-sectional schematic diagram of an electronic device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0037] See also Figure 1 The present invention provides an ultrasonic fingerprint module 100, which includes an ultrasonic detection layer 10 and an ink layer 20. The ultrasonic detection layer 10 has an ultrasonic receiving surface 11. The ink layer 20 is formed on a side of the ultrasonic detection layer 10 away from the ultrasonic receiving surface 11. The ink layer 20 can block ultrasonic waves from being emitted from a side away from the ultrasonic detection layer 10, and can reflect ultrasonic signals transmitted from the ultrasonic detection layer 10 to the ultrasonic detection layer 10.

[0038] It is understandable that the ultrasonic fingerprint module 100 can detect the user's fingerprint using ultrasonic signals, thereby identifying the user's fingerprint image. The ultrasonic fingerprint module 100 can be applied to electronic devices, which can be mobile phones, tablet computers, laptop computers, media players and other devices, or financial terminal devices such as automated teller machines (ATMs).

[0039] By setting an ink layer 20 on the ultrasonic detection layer 10 of the ultrasonic fingerprint module 100, the ink layer 20 can resist and reflect the ultrasonic signal, so that the ultrasonic signal received by the ultrasonic detection layer 10 is strengthened, thereby improving the ultrasonic detection layer 10's efficiency in receiving ultrasonic signals and improving fingerprint recognition efficiency.

[0040] In this embodiment, the ultrasonic detection layer 10 can send ultrasonic signals and sense ultrasonic signals to identify user fingerprints. The ultrasonic detection layer 10 can emit a first ultrasonic signal 01 toward the side away from the ink layer 20, and emit a second ultrasonic signal 02 toward the ink layer 20. When the ultrasonic fingerprint module 100 is applied to an electronic device, when the user's finger is close to the side of the ultrasonic fingerprint module 100 away from the ink layer 20, the first ultrasonic signal 01 is emitted toward the user's fingerprint, and the second ultrasonic signal 02 is blocked by the ink layer 20 and reflected back toward the ultrasonic detection layer 10 to form a third ultrasonic signal 03. The third ultrasonic signal 03 is also emitted toward the user's fingerprint. The third ultrasonic signal 03 and the first ultrasonic signal 01 can resonate and then be emitted toward the user's fingerprint together.

[0041] It is understandable that after receiving the resonant ultrasonic signal, the user's fingerprint reflects the ultrasonic signal back to the ultrasonic detection layer 10, so that the fingerprint detection signal sensed by the ultrasonic detection layer 10 is enhanced. The ultrasonic detection layer 10 receives the ultrasonic detection signal through the ultrasonic receiving surface 11 to obtain the user's fingerprint image. Since the user's fingerprint has a wave region and a valley region, the wave region and the valley region have different reflectivities to the ultrasonic initial signal. The ultrasonic detection signal reflected by the user's fingerprint has a wave signal that can reflect the wave region and a valley signal that can reflect the valley region. The wave signal is compared with the valley signal, and the difference data between the wave signal and the valley signal is obtained and processed to obtain the user's fingerprint image.

[0042] In this embodiment, the ultrasonic detection layer 10 roughly forms a fingerprint recognition area in the area covered by the ultrasonic fingerprint module 100. The ultrasonic fingerprint module 100 adopts a large-area ultrasonic detection layer 10, so that the length dimension of the fingerprint recognition area of ​​the ultrasonic fingerprint module 100 can be 30mm and the width dimension can be 20mm. Compared with the current fingerprint modules with smaller fingerprint recognition areas, the ultrasonic fingerprint module 100 has a larger fingerprint recognition area, which can be applied to large-area fingerprint unlocking scenarios, and can realize fingerprint blind unlocking, and conveniently use fingerprint unlocking to control the startup of electronic equipment programs. For example, the ultrasonic fingerprint module 100 is more suitable for full-screen mobile phones to meet the needs of large-area fingerprint recognition. Of course, in other embodiments, the length of the fingerprint recognition area of ​​the ultrasonic fingerprint module 100 can also be 40mm or greater than 40mm, and the width dimension can be 30mm or greater than 30mm.

[0043] In this embodiment, since the fingerprint recognition area of ​​the fingerprint recognition module 100 is increased, the area of ​​the fingerprint detection layer 10 is increased. The ink layer 20 can be formed on the fingerprint detection layer 10 by a large-area processing process such as a printing process, a vacuum evaporation process, or a spraying process, so as to avoid bubbles at the interface between the ink layer 20 and the fingerprint detection layer 10, and avoid uneven ultrasonic reflection efficiency caused by bubbles, thereby ensuring the effectiveness of fingerprint recognition. The ink layer 20 can be an insulating ink. The ink layer 20 is in contact with the air on one side away from the ultrasonic detection layer, and the interface between the ink layer 20 and the air forms an ultrasonic reflection surface. The difference between the acoustic impedance of the ink layer 20 and the acoustic impedance of the air is used, and the greater the difference, the higher the ultrasonic reflectivity of the interface between the ink layer 20 and the air. The acoustic impedance of the ink layer 20 is proportional to the elastic modulus, so the greater the elastic modulus of the ink layer 20, the greater the acoustic impedance of the ink layer 20. In this embodiment, the elastic modulus of the ink layer 20 is set to be roughly equivalent to the elastic modulus of the plastic film, so that the ink layer 20 has a good shielding effect on ultrasonic signals, and the interface between the ink layer 20 and the air has a good reflection efficiency for ultrasonic waves. The ink layer 20 resists and reflects the ultrasonic signal emitted by the ultrasonic detection layer 10, so that the ultrasonic wave received by the user's fingerprint is strengthened, and the ultrasonic wave reflected from the user's fingerprint is received by the ultrasonic detection layer 10. The recognition efficiency of the ultrasonic detection layer 10 is improved. The ink layer 20 also has the function of protecting the ultrasonic detection layer 10, ensuring the safety of the ultrasonic detection layer 10. The ink layer 20 also has the performance of resisting ultrasonic waves transmitted from the external air, realizing the resistance of ultrasonic signals in the external environment, preventing environmental ultrasonic waves from interfering with the ultrasonic detection layer 10 in identifying the ultrasonic signal reflected from the user's fingerprint, and ensuring the accuracy of the ultrasonic detection layer 10 in identifying the user's fingerprint.

[0044] It is understandable that the ink layer 20 is provided with a resin material, for example, the ink layer 20 is provided with any one or more combination materials of acrylic resin, polyester resin, isocyanate resin, phenolic resin, and epoxy resin. As a preferred embodiment, the ink layer 20 is provided with an epoxy resin material. The ink layer 20 utilizes the insulating property of the resin material to ensure that the ink layer 20 can perform the function of insulating and protecting the ultrasonic detection layer, and utilizes the elastic modulus of the cured resin material similar to that of the plastic sheet to ensure that the ink layer 20 has substantially the same ultrasonic reflection efficiency as that of the plastic sheet.

[0045] In the process of selecting the material of the ink layer 20, ink layers 20 of various materials can be formed on multiple groups of fingerprint detection layers 10 by screen printing process to obtain multiple groups of ultrasonic fingerprint detection module 100 samples. By performing SNR (SIGNAL NOISE RATIO) value detection on multiple groups of ultrasonic fingerprint detection module 100 samples, the SNR average value of the samples of multiple groups of ultrasonic fingerprint detection modules 100 is obtained, and then the material of the ink layer 20 with the best SNR average value is selected after comparing the multiple groups of SNR average values. The SNR value can be tested by an ultrasonic fingerprint test instrument.

[0046] Specifically, a first group of ultrasonic fingerprint module 100 samples is provided, and the ink layer 20 of the group of samples adopts acrylic resin. A second group of ultrasonic fingerprint module 100 samples is provided, and the ink layer 20 of the group of samples adopts polyester resin. A third group of ultrasonic fingerprint module 100 samples is provided, and the ink layer 20 of the group of samples adopts a mixed resin of acrylic resin, isocyanate resin and polyester resin. A fourth group of ultrasonic fingerprint module 100 samples is provided, and the ink layer 20 of the group of samples adopts phenolic resin. A fifth group of ultrasonic fingerprint module 100 samples is provided, and the ink layer 20 of the group of samples adopts epoxy resin 1, and epoxy resin 1 can be a conventional epoxy resin. A sixth group of ultrasonic fingerprint module 100 samples is provided, and the ink layer 20 of the group of samples adopts epoxy resin 2, and the specifications of epoxy resin 2 and epoxy resin 1 are different, and the CAS number of epoxy resin 2 is 38891-59-7. The average SNR values ​​of the first, second, third, fourth, fifth and sixth groups of samples were 8.10, 3.77, 7.38, 8.54, 8.89 and 10.33 respectively. The SNR values ​​of the samples in the first group were 8.10, 8.75, 8.85, 7.48, 7.45, 7.89 and 8.16 respectively. The SNR values ​​of the samples in the second group were 3.77, 3.89, 3.87, 3.22, 3.93, 4.08 and 3.61 respectively. The SNR values ​​of the samples in the third group were 7.38, 8.18, 7.09, 7.75, 7.39, 6.84 and 7.02 respectively. The SNR values ​​of the samples in the fourth group were 8.54, 8.65, 9.01, 8.76, 7.68, 8.68 and 8.46 respectively. The SNR values ​​of the samples in the fifth group are 8.89, 8.89, 8.33, 8.07, 9.69, 8.94, and 9.40, respectively. The SNR values ​​of the samples in the sixth group are 10.33, 9.63, 10.47, 10.99, 10.56, 10.03, and 10.32, respectively. It is further obtained that the average SNR values ​​of the first, second, third, fourth, fifth, and sixth groups of samples are 8.10, 3.77, 7.38, 8.54, 8.89, and 10.33, respectively. It can be seen that the ink layer 20 of the sixth group of ultrasonic fingerprint module 100 samples uses epoxy resin 2, and its SNR average value is the best. Therefore, the use of epoxy resin 2 as the material of the ink layer 20 can make the fingerprint recognition efficiency of the ultrasonic fingerprint module 100 better. Among them, the difference between epoxy resin 1 and epoxy resin 2 is that the specifications are different. Specifically, the CAS number of the epoxy resin 2 is 38891-59-7.

[0047] The ultrasonic detection layer 10 has a detection layer bottom surface 12 opposite to the ultrasonic receiving surface 11, and the ink layer 20 is formed on the detection layer bottom surface 12 by a printing process. The ink layer 20 can be formed on the detection layer bottom surface 12 by a TFT (Thin Film Transistor) printing process. The ink layer 20 can be formed by a printing process, so that the ink layer 20 can be formed in a large area, and a plurality of ultrasonic fingerprint modules 100 can be printed and formed at one time, and ultrasonic fingerprint modules 100 can be obtained in batches after cutting, thereby improving production efficiency. Specifically, a large-area ultrasonic detection layer 10 is first formed, and then a large-area ink layer 20 is printed and formed on the large-area ultrasonic detection layer 10, and then the large-area ultrasonic detection layer 10 and the large-area ink layer 20 are cut together to form a plurality of ultrasonic fingerprint modules 100, so as to realize rapid batch production of ultrasonic fingerprint modules 100, reduce production costs, and improve efficiency.

[0048] Furthermore, the ink layer 20 is formed by adding carbon powder particles into the resin material so that the ink layer 20 presents a black appearance.

[0049] In this embodiment, the resin material and the carbon powder are mixed to form a liquid ink, and then the liquid ink is formed on the ultrasonic fingerprint detection layer 10 by a screen printing process and cured to form the ink layer 20. The elastic modulus of the ink layer 20 is determined according to the ultrasonic frequency emitted by the ultrasonic detection layer 10, so that the elastic modulus of the ink layer 20 matches the ultrasonic frequency. By setting the elastic modulus of the ink layer 20, the ink layer 20 can resist and reflect the ultrasonic signal to improve the fingerprint recognition efficiency of the ultrasonic fingerprint module 100. Since the ink layer 20 contains black carbon powder, the ink layer 20 presents a black appearance visual effect, so that the ink layer 20 can block the transmission of visible light, that is, the ink layer 20 can cover the ultrasonic fingerprint detection layer 10, so that the appearance defects of the ultrasonic fingerprint detection layer 10 are invisible, and the appearance performance of the ultrasonic fingerprint module 100 is improved. The ink layer 20 can be formed by printing a layer structure of a liquid printing material and then forming it by a curing process. Specifically, first, a liquid resin material and a black carbon powder material mixed with the liquid resin material are provided. Then, the liquid resin material mixed with the black carbon powder material is printed and formed on the bottom surface 12 of the detection layer of the ultrasonic detection layer 10 by a printing device. Finally, the liquid layered ink layer 20 is solidified to obtain a solid ink layer 20. Of course, in other embodiments, the ink layer 20 may also be composed of insulating glue and white carbon powder, or red carbon powder, or green carbon powder mixed with the insulating glue. The ink layer 20 may also be composed of other materials with ultrasonic shielding properties mixed with colored particles. Of course, in other embodiments, the ink layer 20 may also be a transparent layer to facilitate the integration of the ultrasonic fingerprint module 100 into the display screen to ensure the display effect of the display screen.

[0050] In this embodiment, the carbon powder particles in the ink layer 20 can fill the gaps between the resin particles in the resin material, thereby reducing the surface roughness of the ink layer 20 and making the surface of the ink layer 20 smooth.

[0051] Specifically, the ink layer 20 has a first surface 201 away from the fingerprint detection layer 10. The first surface 201 is in contact with the air. The first surface 201 is smoothly arranged, and the roughness of the first surface 201 is 0.2Rz / μm to 6.0Rz / μm. For example, the roughness of the first surface 201 may be 0.41Rz / μm, or 0.68Rz / μm, or 4.76Rz / μm, or 5.25Rz / μm. The ink layer 20 has a second surface 202 opposite to the first surface 201. The second surface 202 is attached to the fingerprint detection layer 10. The second surface 202 is smoothly arranged, and the roughness of the second surface is 0.2Rz / μm to 6.0Rz / μm. For example, the roughness of the first surface 201 may be 0.41Rz / μm, or 0.68Rz / μm, or 4.76Rz / μm, or 5.25Rz / μm. The smaller the roughness of the first surface 201, the smaller the unevenness of the first surface 201, that is, the smoother the first surface, the less likely the ultrasonic wave will be diffusely reflected on the first surface 201, and the reflection direction of the ultrasonic wave on the first surface 201 will be approximately consistent, so that the ultrasonic interference signal received by the ultrasonic detection layer 10 is smaller, thereby improving the fingerprint recognition clarity of the ultrasonic fingerprint module 100. Similarly, the smaller the roughness of the second surface 202, the less likely the ultrasonic wave will be diffusely reflected when passing through the second surface 202, thereby improving the fingerprint recognition efficiency of the ultrasonic fingerprint module 100.

[0052] It is understandable that the larger the average particle size of the carbon powder particles in the ink layer 20, the easier it is to increase the roughness of the first surface 201 and the second surface 202 of the ink layer 20, and the easier it is to cause the first surface 201 to form diffuse reflection of ultrasound, and the easier it is to cause the second surface 202 to form diffuse reflection of ultrasound. Therefore, by setting the average particle size of the carbon powder particles in the ink layer 20 and setting the proportion of the carbon powder particles in the ink layer 20, the roughness of the first surface 201 and the roughness of the second surface 202 can be improved.

[0053] In this embodiment, the average particle size of the carbon powder particles in the ink layer 20 is 0.5 microns to 5 microns. When the average particle size of the carbon powder particles in the ink layer 20 is 0.5 microns, the roughness of the ink layer 20 can be reduced to a minimum, but the OD value of the ultrasonic fingerprint module 100 is not optimal. When the average particle size of the carbon powder particles in the ink layer 20 is 5 microns, the OD value of the ultrasonic fingerprint module 100 is excellent, but the roughness of the ink layer 20 is not optimal. As a preferred embodiment, the average particle size of the carbon powder particles in the ink layer 20 is 0.8 microns to 2 microns, and further 1.0 microns. It can be understood that when the average particle size of the carbon powder particles in the ink layer 20 is 0.8 microns, the roughness of the ink layer 20 can be close to the minimum value, and the OD value of the ultrasonic fingerprint module 100 meets the performance requirements. When the average particle size of the carbon powder particles in the ink layer 20 is 2 microns, the OD value of the ultrasonic fingerprint module 100 is relatively excellent, and the roughness of the ink layer 20 can also be relatively reduced. Furthermore, when the average particle size of the carbon powder particles in the ink layer 20 is 1 micron, the roughness of the ink layer 20 can be close to the minimum value, and the OD value and SNR value of the ultrasonic fingerprint module 100 can be relatively excellent. Of course, the average particle size of the carbon powder particles in the ink layer 20 can also be approximately 1 micron, the roughness of the ink layer 20 can be close to the minimum value, and the OD value and SNR value of the ultrasonic fingerprint module 100 can also be relatively excellent.

[0054] In this embodiment, the mass proportion of the carbon powder particles in the ink layer 20 is 2.5% to 15%. When the mass proportion of the carbon powder particles in the ink layer 20 is 2.5%, the roughness of the ink layer 20 can be reduced to the minimum, but the OD value of the ultrasonic fingerprint module 100 is not optimal. When the mass proportion of the carbon powder particles in the ink layer 20 is 15%, the OD value of the ultrasonic fingerprint module 100 is high, but the roughness of the ink layer 20 is not the minimum. As a preferred embodiment, the mass proportion of the carbon powder particles in the ink layer is 3.0% to 10%, and further 5%. It can be understood that when the mass proportion of the carbon powder particles in the ink layer 20 is 3.0%, the roughness of the ink layer 20 can be close to the minimum value, and the OD value of the ultrasonic fingerprint module 100 meets the performance requirements. When the mass proportion of the carbon powder particles in the ink layer 20 is 10%, the OD value of the ultrasonic fingerprint module 100 meets the requirements, and the roughness of the ink layer 20 can also be reduced. Furthermore, when the mass proportion of the carbon powder particles in the ink layer 20 is 5%, the roughness of the ink layer 20 can be close to the minimum value, and the OD value and SNR value of the ultrasonic fingerprint module 100 can be relatively excellent. Of course, the mass proportion of the carbon powder particles in the ink layer 20 can be approximately 5%, the roughness of the ink layer 20 can be close to the minimum value, and the OD value and SNR value of the ultrasonic fingerprint module 100 can also be relatively excellent.

[0055] In order to further improve the roughness of the first surface 201 and the roughness of the second surface 202. A leveling agent is added during the preparation of the ink layer 20 to utilize the surface defoaming, surface flatness control and good surface leveling properties of the leveling agent to effectively reduce the surface roughness of the ink layer 20. That is, the ink layer 20 also contains a leveling agent, which is used to improve the leveling of the ink layer formed during the production process and in the end. The mass proportion of the leveling agent in the ink layer 20 can be 0.2% to 1.5%. The leveling agent can be a fluorocarbon leveling agent, and the leveling agent can be a fluorocarbon organic modified siloxane. The leveling agent can also be a polyether siloxane copolymer. As a preferred embodiment, the leveling agent can be a mixture of a fluorocarbon organic modified siloxane and a polyether siloxane copolymer. The mass proportion of the fluorocarbon organic modified siloxane can be 0.1% to 0.75%, and the mass proportion of the polyether siloxane copolymer can be 0.1% to 0.75%. When the mass proportion of the fluorocarbon organic modified siloxane is 5% and the mass proportion of the polyether siloxane copolymer is 5%, the polyether siloxane copolymer and the fluorocarbon siloxane have good complementarity, the polyether siloxane copolymer has strong surface state control ability, good surface leveling, and a certain defoaming effect. The ink layer 20 has good leveling, a smooth surface, and a surface roughness that can be controlled to be less than <0.5Rz / μm, and the fingerprint recognition efficiency of the ultrasonic fingerprint module 100 is improved.

[0056] A first embodiment is provided, in which the average particle size of 50% of the particle size distribution of the carbon powder particles arranged in the ink layer 20 is 5μm. The mass proportion of the carbon powder in the ink layer 20 is 15%. The leveling agent in the ink layer 20 adopts fluorocarbon organic modified siloxane. The mass proportion of the leveling agent in the ink layer 20 is 0.2%. The roughness tester was used to test the roughness of the ink layer 20 of the ultrasonic fingerprint module 100 in this embodiment, and the test result was that the roughness of the ink layer 20 was 5.25Rz / μm. The ultrasonic fingerprint function tester was used to test the SNR value of the ultrasonic fingerprint module 100 in this embodiment, and the SNR value obtained was 9.45. The OD (optical density) value of the ultrasonic fingerprint module 100 in this embodiment was tested using an optical densitometer, and the OD value obtained was 6.1.

[0057] A second embodiment is provided, which is different from the first embodiment in that the mass proportion of carbon powder in the ink layer 20 is reduced. The average particle size of 50% of the particle size distribution of the carbon powder particles in the ink layer 20 is 5μm. The mass proportion of carbon powder in the ink layer 20 is 10%. The leveling agent in the ink layer 20 adopts fluorocarbon organic modified siloxane. The mass proportion of the leveling agent in the ink layer 20 is 0.2%. The roughness of the ink layer 20 is 5.04Rz / μm. The SNR value of the ultrasonic fingerprint module 100 is 9.52. The OD value of the ultrasonic fingerprint module 100 is 5.3. It can be seen that reducing the carbon powder proportion of the ink layer 20 can reduce the surface roughness of the ink layer 20.

[0058] It can be understood that when the OD value of the ultrasonic fingerprint module 100 is greater than 4, the performance of the ultrasonic fingerprint module 100 is relatively good.

[0059] A third embodiment is provided, which is different from the second embodiment in that the mass proportion of carbon powder in the ink layer 20 is further reduced. The average particle size of 50% of the particle size distribution of carbon powder particles set in the ink layer 20 is 5μm. The mass proportion of carbon powder in the ink layer 20 is 5%. The leveling agent in the ink layer 20 adopts fluorocarbon organic modified siloxane. The mass proportion of the leveling agent in the ink layer 20 is 0.2%. The roughness of the ink layer 20 is 4.76Rz / μm. The SNR value of the ultrasonic fingerprint module 100 is 9.65. The OD value of the ultrasonic fingerprint module 100 is 4.6. It can be seen that reducing the mass proportion of carbon powder in the ink layer 20 can reduce the surface roughness of the ink layer 20 and improve the SNR value of the ultrasonic fingerprint module 100, but it will also reduce the OD value of the ultrasonic fingerprint module 100.

[0060] A fourth embodiment is provided, which is different from the third embodiment in that the mass proportion of carbon powder in the ink layer 20 is further reduced. The average particle size of 50% of the particle size distribution of carbon powder particles set in the ink layer 20 is 5μm. The mass proportion of carbon powder in the ink layer 20 is 2.5%. The leveling agent in the ink layer 20 adopts fluorocarbon organic modified siloxane. The mass proportion of the leveling agent in the ink layer 20 is 0.2%. The roughness of the ink layer 20 is 4.42Rz / μm. The SNR value of the ultrasonic fingerprint module 100 is 9.7. The OD value of the ultrasonic fingerprint module 100 is 3.7. It can be seen that when the mass proportion of carbon powder in the ink layer 20 is reduced to 2.5%, the OD value of the ultrasonic fingerprint module 100 is also reduced to 3.7, and the ultrasonic fingerprint module 100 no longer meets the good performance requirements.

[0061] A fifth embodiment is provided, which is different from the fourth embodiment in that the average particle size of the carbon powder in the ink layer 20 is reduced. The average particle size of 50% of the particle size distribution of the carbon powder particles in the ink layer 20 is 0.5μm. The average particle size of 100% of the particle size distribution of the carbon powder particles in the ink layer 20 is less than 1μm. The mass proportion of carbon powder in the ink layer 20 is 5%. The leveling agent in the ink layer 20 adopts fluorocarbon organic modified siloxane. The mass proportion of the leveling agent in the ink layer 20 is 0.2%. The roughness of the ink layer 20 is 0.82Rz / μm. The SNR value of the ultrasonic fingerprint module 100 is 10.25. The OD value of the ultrasonic fingerprint module 100 is 4.3. It can be seen that when the average particle size of the carbon powder in the ink layer 20 is reduced, the surface roughness of the ink layer 20 can be significantly reduced, and the SNR value of the ultrasonic fingerprint module 100 can be guaranteed to be high, and the OD value of the ultrasonic fingerprint module 100 also meets the good performance requirements, that is, the performance of the ultrasonic fingerprint module 100 is significantly improved.

[0062] A sixth embodiment is provided, which is different from the fifth embodiment in that the proportion of the leveling agent in the ink layer 20 is increased. The average particle size of 50% of the particle size distribution of the carbon powder particles in the ink layer 20 is 0.5 μm. The average particle size of 100% of the particle size distribution of the carbon powder particles in the ink layer 20 is less than 1 μm. The mass proportion of carbon powder in the ink layer 20 is 5%. The leveling agent in the ink layer 20 adopts fluorocarbon organic modified siloxane. The mass proportion of the leveling agent in the ink layer 20 is 0.7%. The roughness of the ink layer 20 is 0.68Rz / μm. The SNR value of the ultrasonic fingerprint module 100 is 10.35. The OD value of the ultrasonic fingerprint module 100 is 4.4. It can be seen that when the mass proportion of the leveling agent in the ink layer 20 increases, the surface roughness of the ink layer 20 will also decrease, and the SNR value of the ultrasonic fingerprint module 100 will increase. The OD value of the ultrasonic fingerprint module 100 will also increase.

[0063] A seventh embodiment is provided, which is different from the sixth embodiment in that the leveling agent in the ink layer 20 is a mixture of two different types of leveling agents. Specifically, the average particle size of 50% of the carbon powder particles in the ink layer 20 is 0.5μm. The average particle size of 100% of the carbon powder particles in the ink layer 20 is less than 1μm. The mass proportion of carbon powder in the ink layer 20 is 5%. The leveling agent in the ink layer 20 adopts a mixed leveling agent of fluorocarbon organic modified siloxane and polyether siloxane copolymer. The mass proportion of fluorocarbon organic modified siloxane in the ink layer 20 is 0.5%. The mass proportion of polyether siloxane copolymer in the ink layer 20 is 0.5%. The roughness of the ink layer 20 is 0.41Rz / μm. The SNR value of the ultrasonic fingerprint module 100 is 10.55. The OD value of the ultrasonic fingerprint module 100 is 4.3. It can be seen that fluorocarbon organic modified siloxane belongs to the fluorocarbon compound leveling agent, which has good substrate wettability and strong anti-shrinkage ability, but this leveling agent is easy to stabilize foam and it is difficult to eliminate foam. After adding various leveling agents to the molding material of the ink layer 20, it was found that there is good complementarity between polyether siloxane copolymer and fluorocarbon siloxane, and the polyether siloxane copolymer has strong surface state control ability, good surface leveling, and a certain defoaming effect. After adding polyether siloxane copolymer and fluorocarbon siloxane to the molding material of the ink layer 20, the leveling property is good, the surface is smooth, and the surface roughness of the ink layer 20 can be controlled to be less than 0.5Rz / μm.

[0064] It is understandable that if there are bubbles in the ink layer 20, the ultrasonic acoustic impedance of the bubbles is very small, resulting in the signal strength of the ultrasonic signal being greatly attenuated or even absent when penetrating and reflecting through the bubbles, that is, the signal receiving strength of the ultrasonic detection layer 10 at the position corresponding to the bubbles in the ink layer 20 is significantly different from that in other areas, resulting in noise in the acquired fingerprint image, that is, the acquired fingerprint image is not clear. Therefore, by improving the bubbles in the ink layer 20, the clarity of the fingerprint image acquired by the ultrasonic fingerprint module 100 can be improved.

[0065] In order to further reduce the number of bubbles in the ink layer 20. A defoamer is added to the molding material of the ink layer 20 to utilize the defoaming performance of the defoamer so that the number of bubbles in the ink layer 20 is reduced. That is, the ink layer 20 also contains a defoamer, which is used to eliminate bubbles in the ink layer during the production process and eliminate bubbles in the ink layer finally formed. The mass proportion of the defoamer in the ink layer 20 can be 1.0% to 3.0%. The defoamer can be modified dimethyl silane, and the defoamer can also be polyoxypropylene oxyethylene glycerol ether. As a preferred embodiment, the defoamer can be a mixture of modified dimethyl silane and polyoxypropylene oxyethylene glycerol ether. The mass proportion of the modified dimethyl silane can be 0.8% to 2.0%, and the mass proportion of the polyoxypropylene oxyethylene glycerol ether can be 0.2% to 1.0%. When the mass proportion of the fluorocarbon organic modified siloxane is 1.5% and the mass proportion of the polyether siloxane copolymer is 0.5% to 1.0%, the ink layer 20 has no bubbles.

[0066] An eighth embodiment is provided, wherein the ink layer 20 is provided with a defoamer. Specifically, the mass proportion of carbon powder in the ink layer 20 is 15%. The defoamer in the ink layer 20 is modified dimethyl silane. The mass proportion of the defoamer in the ink layer 20 is 0.5%. A large number of bubbles exist in the molding material of the ink layer 20 after adding the defoamer and stirring. After the molding material of the ink layer 20 after stirring is printed and formed on the fingerprint detection layer 10 by screen printing, a large number of bubbles still exist in the ink layer 20. The OD value of the ultrasonic fingerprint module 100 is 6.1.

[0067] A ninth embodiment is provided, which is different from the eighth embodiment in that the mass proportion of carbon powder in the ink layer 20 is reduced, and the mass proportion of the defoamer in the ink layer 20 is increased. Specifically, the mass proportion of carbon powder in the ink layer 20 is 10%. The defoamer in the ink layer 20 is modified dimethyl silane. The mass proportion of the defoamer in the ink layer 20 is 0.8%. A small amount of bubbles exist in the molding material of the ink layer 20 after adding the defoamer and stirring. After the molding material of the ink layer 20 after stirring is printed and molded on the fingerprint detection layer 10 by screen printing, a small amount of bubbles still exist in the ink layer 20. The OD value of the ultrasonic fingerprint module 100 is 5.3. It can be seen that the higher the mass proportion of carbon powder in the ink layer 20, the easier it is for the ink layer 20 to generate bubbles during the preparation process. By reducing the mass proportion of carbon powder in the ink layer 20 and increasing the mass proportion of the defoamer in the ink layer 20, the bubble content in the ink layer 20 can be improved.

[0068] A tenth embodiment is provided, which is different from the ninth embodiment in that the mass proportion of carbon powder in the ink layer 20 is further reduced, and the mass proportion of defoamer in the ink layer 20 is further increased. Specifically, the mass proportion of carbon powder in the ink layer 20 is 5%. The defoamer in the ink layer 20 is modified dimethyl silane. The mass proportion of defoamer in the ink layer 20 is 1.5%. After the molding material of the ink layer 20 is added with defoamer and stirred, there are very few bubbles. After the molding material of the ink layer 20 after stirring is printed and formed on the fingerprint detection layer 10 by screen printing, there are still very few bubbles in the ink layer 20. The OD value of the ultrasonic fingerprint module 100 is 4.6. It can be seen that by reducing the mass proportion of carbon powder in the ink layer 20 and increasing the mass proportion of defoamer in the ink layer 20, the bubble content in the ink layer 20 can be significantly improved, but at the same time, the OD value of the ultrasonic fingerprint module 100 will be significantly reduced, which is easy to cause the performance of the ultrasonic fingerprint module 100 to be reduced.

[0069] An eleventh embodiment is provided, which is different from the tenth embodiment in that the mass proportion of carbon powder in the ink layer 20 continues to decrease, and the mass proportion of the defoamer in the ink layer 20 continues to increase. Specifically, the mass proportion of carbon powder in the ink layer 20 is 2.5%. The defoamer in the ink layer 20 is modified dimethyl silane. The mass proportion of the defoamer in the ink layer 20 is 2.0%. After the molding material of the ink layer 20 is added with the defoamer and stirred, there are very few bubbles. After the molding material of the ink layer 20 after stirring is printed and formed on the fingerprint detection layer 10 by screen printing, there are still very few bubbles in the ink layer 20. The OD value of the ultrasonic fingerprint module 100 is 3.7. When the mass proportion of the defoamer in the ink layer 20 is 2.0%, the ink layer 20 obviously has shrinkage holes. It can be seen that when the mass proportion of the defoamer in the ink layer 20 is greater than 2.0%, the ink layer 20 cannot meet the use requirements. The mass proportion of carbon powder in the ink layer 20 is greater than or equal to 5%, and the mass proportion of the defoaming agent in the ink layer 20 is increased to approximately 1.5%, so that the OD value of the ultrasonic fingerprint module 100 meets the minimum requirement, but it still cannot ensure that the ink layer 20 is free of bubbles.

[0070] A twelfth embodiment is provided, which is different from the eleventh embodiment in that the defoamer in the ink layer 20 includes two different types of defoamers. Specifically, the mass proportion of carbon powder in the ink layer 20 is 5%. The defoamer in the ink layer 20 is a mixture of modified dimethyl silane and polyoxypropylene oxyethylene glycerol ether. The mass proportion of modified dimethyl silane in the ink layer 20 is 1.5%. The mass proportion of polyoxypropylene oxyethylene glycerol ether in the ink layer 20 is 0.2%. After the molding material of the ink layer 20 is added with the defoamer and stirred, there are no bubbles. After the molding material of the ink layer 20 after stirring is printed and formed on the fingerprint detection layer 10 by screen printing, there are still very few bubbles in the ink layer 20. The OD value of the ultrasonic fingerprint module 100 is 4.5. It can be seen that the defoaming agent in the ink layer 20 includes modified dimethyl silane and polyoxypropylene oxyethylene glycerol ether, so that the bubble content of the ink layer 20 can be significantly improved during the preparation process, and the OD value of the ultrasonic fingerprint module 100 also meets the performance requirements, but there are still very few bubbles in the finally formed ink layer 20.

[0071] A thirteenth embodiment is provided, which is different from the twelfth embodiment in that the mass proportion of polyoxypropylene oxyethylene glycerol ether in the molding material of the ink layer 20 is increased. Specifically, the mass proportion of carbon powder in the ink layer 20 is 5%. The defoamer in the ink layer 20 is a mixture of modified dimethyl silane and polyoxypropylene oxyethylene glycerol ether. The mass proportion of modified dimethyl silane in the ink layer 20 is 1.5%. The mass proportion of polyoxypropylene oxyethylene glycerol ether in the ink layer 20 is 0.5%. After the molding material of the ink layer 20 is added with the defoamer and stirred, there are no bubbles. After the molding material of the ink layer 20 after stirring is printed and formed on the fingerprint detection layer 10 by screen printing, there are no bubbles in the ink layer 20. The OD value of the ultrasonic fingerprint module 100 is 4.6. It can be seen that by including modified dimethyl silane and polyoxypropylene oxyethylene glycerol ether in the defoaming agent in the ink layer 20 and increasing the mass proportion of polyoxypropylene oxyethylene glycerol ether, the ink layer 20 can be free of bubbles during the preparation process, the final formed ink layer 20 is free of bubbles, and the OD value of the ultrasonic fingerprint module 100 also meets the performance requirements, so that the performance of the ultrasonic fingerprint module 100 is significantly improved.

[0072] A fourteenth embodiment is provided, which is different from the thirteenth embodiment in that the mass proportion of polyoxypropylene oxyethylene glycerol ether in the ink layer 20 continues to increase. Specifically, the mass proportion of carbon powder in the ink layer 20 is 5%. The defoamer in the ink layer 20 is a mixture of modified dimethyl silane and polyoxypropylene oxyethylene glycerol ether. The mass proportion of modified dimethyl silane in the ink layer 20 is 1.5%. The mass proportion of polyoxypropylene oxyethylene glycerol ether in the ink layer 20 is 1.0%. After the defoamer is added to the molding material of the ink layer 20 and stirred, there are no bubbles. After the molding material of the ink layer 20 after stirring is printed and formed on the fingerprint detection layer 10 by screen printing, there are no bubbles in the ink layer 20. The OD value of the ultrasonic fingerprint module 100 is 4.6.

[0073] For further information, see Figure 2 The ultrasonic detection layer 10 includes a substrate layer 13, a plurality of pixel electrodes 14, a piezoelectric layer 15 and a conductive electrode 16. The plurality of pixel electrodes 14 are arranged in an array on the substrate layer 13. The piezoelectric layer 15 covers the plurality of pixel electrodes 14. The conductive electrode 16 is stacked on a side of the piezoelectric layer 15 away from the plurality of pixel electrodes 14. The ink layer 20 is printed and formed on a side of the conductive electrode 16 away from the piezoelectric layer 15.

[0074] In this embodiment, the substrate layer 13 can be made of glass or polyimide film material. The substrate layer 13 has low cost and good light transmittance, which facilitates the integration of the ultrasonic fingerprint module 100 into the display screen of the electronic device. When the ultrasonic fingerprint module 100 is integrated into the display screen, the ultrasonic fingerprint module 100 with good light transmittance will not block the display image of the display screen 90. At the same time, the ultrasonic fingerprint module 100 integrated into the display screen 90 can maintain the overall color of the display screen 90 and improve the appearance performance of the display screen 90.

[0075] In this embodiment, a plurality of the pixel electrodes 14 can be formed on the substrate layer 13 by TFT printing process and are distributed in an array. The material of the pixel electrode 14 is any one of indium tin oxide (ITO), nano silver wire (Agnanowire), metal mesh, nano carbon tube and graphene. The pixel electrode 14 made of the above materials has good toughness and light transmittance. The ultrasonic fingerprint module 100 made of the pixel electrode 14 has good toughness and light transmittance. The light transmittance of the pixel electrode 14 is greater than 90%, so that the ultrasonic fingerprint module 100 made of the pixel electrode 14 has good light transmittance. The pixel electrode 14 can be used to receive electrical signals, and each pixel electrode 14 can determine a position of the ultrasonic fingerprint module 100 according to the received electrical signal. The density of the pixel electrode 14 on the substrate layer 13 is positively correlated with the fingerprint collection accuracy of the ultrasonic fingerprint module 100. The dense array arrangement of the plurality of pixel electrodes 14 ensures the accuracy of the fingerprint image of the object to be detected by the ultrasonic sensor.

[0076] In this embodiment, the ultrasonic receiving surface 11 is arranged on the side of the piezoelectric layer 15 facing the substrate layer 13. The piezoelectric layer 15 is stacked on the substrate layer 13 and covers the multiple pixel electrodes 14. The piezoelectric layer 15 is a sheet structure made of piezoelectric material. The shape of the piezoelectric layer 15 matches the shape of the substrate layer 13. The material of the piezoelectric layer 15 is polyvinylidene fluoride (PVDF). Since polyvinylidene fluoride has good toughness and light transmittance, the piezoelectric layer 15 has good flexibility and light transmittance, which ensures the flexibility and light transmittance of the ultrasonic fingerprint module 100. The piezoelectric layer 15 can generate ultrasonic waves under the action of high-frequency voltage (for example, a voltage with a frequency greater than 20KHZ). After the piezoelectric layer 15 receives the ultrasonic wave reflected by the object to be detected, the piezoelectric layer 15 will generate an electrical signal (or piezoelectric signal) under the action of the ultrasonic wave, and the object to be detected can be a finger, a test template, etc.

[0077] In this embodiment, the conductive electrode 16 is an integral layered structure made of a conductive material. The shape of the conductive electrode 16 matches the shape of the piezoelectric layer 15. The material of the conductive electrode 16 can be a silver material. The conductive electrode 16 can be formed after the silver paste is cured. The transmittance of the conductive electrode 16 is greater than 90%. After the conductive electrode 16 and the pixel electrode 14 are connected to a high-frequency voltage, a high-frequency voltage can be applied to the piezoelectric layer 15, so that the piezoelectric layer 15 generates an ultrasonic signal, so as to facilitate the use of ultrasonic signals to detect user fingerprints. The conductive electrode 16 and the pixel electrode 14 can also receive the electrical signal generated by the piezoelectric layer 15. The bottom surface 12 of the detection layer is arranged on the side of the conductive electrode 16 away from the piezoelectric layer 15. The ink layer 20 covers the conductive electrode 16 to prevent the conductive electrode 16 from oxidation. The ink layer 20 can also cover the appearance defects on the conductive electrode 16.

[0078] In this embodiment, the thickness of the conductive electrode 16 is 10 microns to 30 microns, the thickness of the piezoelectric layer 15 is 5 microns to 15 microns, and the thickness of the substrate layer 13 is 80 microns to 100 microns. The thickness of the ink layer 20 is 7 microns to 30 microns. The thin performance of the ultrasonic fingerprint module 100 facilitates the integration of the ultrasonic fingerprint module 100 into the display screen of an electronic device.

[0079] It is understandable that the ink layer 20 is printed on the fingerprint detection layer 10 , that is, the ink layer 20 is printed on the conductive electrode 16 . The surface roughness of the conductive electrode 16 affects the roughness of the first surface 201 of the ink layer 20 .

[0080] After testing, ink layers 20 with different thicknesses were formed on a glass substrate with a smaller surface roughness, and the surface roughness of the formed ink layer 20 was measured, and it was found that the surface roughness of the formed ink layer 20 was not greatly affected by the thickness of the ink layer 20. For example, ink layers 20 with film thicknesses of 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, and 30 μm were formed on the glass substrate, and the surface roughness of the formed ink layer 20 was 0.375 Rz / μm, 0.355 Rz / μm, 0.335 Rz / μm, 0.315 Rz / μm, 0.316 Rz / μm, and 0.322 Rz / μm, respectively.

[0081] After testing, multiple ink layers 20 with different thicknesses were formed on multiple fingerprint detection layers 10 respectively, and finally multiple ultrasonic fingerprint modules 100 were obtained. The surface roughness of the ink layer 20 of the ultrasonic fingerprint module 100 was measured, and it was found that the thicker the ink layer 20, the smaller the surface roughness of the ink layer 20, and when the thickness of the ink layer 20 is approximately 25μm, the surface roughness of the ink layer 20 does not decrease as the thickness of the ink layer 20 decreases, that is, the surface roughness of the ink layer 20 tends to be stable and no longer decreases.

[0082] In one embodiment, the surface roughness of the six fingerprint detection layers 10 facing the ink layer 20 is 3.5Rz / μm to 4.5Rz / μm. The thickness of the substrate layer 13 in the six fingerprint detection layers 10 is 90μm, the thickness of the piezoelectric layer 15 is 9μm, and the thickness of the conductive electrode 16 is 15 to 18μm. Six ink layers 20 with film thicknesses of 5μm, 10μm, 15μm, 20μm, 25μm, and 30μm are formed on the six fingerprint detection layers 10, and the surface roughness of the six ink layers 20 after forming is tested to be 1.712Rz / μm, 1.06Rz / μm, 0.72Rz / μm, 0.527Rz / μm, 0.309Rz / μm, and 0.324Rz / μm, respectively. Obviously, when the thickness of the ink layer 20 is between 20 μm and 30 μm, the surface roughness of the ink layer 20 of the ultrasonic fingerprint module 100 is relatively small, and the performance of the ultrasonic fingerprint module 100 is excellent.

[0083] In another embodiment, Figure 3 As shown, the ink layer 20 is provided with a plurality of sub-ink layers 22, and the plurality of sub-ink layers 22 are sequentially stacked.

[0084] In this embodiment, the ink layer 20 is formed by multiple printing steps, and each printing step forms each sub-ink layer 22. After each sub-ink layer 22 is solidified, another sub-ink layer 22 is formed. The thickness of each sub-ink layer 22 can be set to be the same. By accurately controlling the surface roughness of each sub-ink layer 22, the surface roughness of the ink layer 20 after final formation can be made better, so as to ensure the excellent performance of the ultrasonic fingerprint module 100.

[0085] See also Figure 4 The present application provides a method for manufacturing an ultrasonic fingerprint module, the method comprising the steps of:

[0086] 101: Provide an ultrasonic detection layer 10.

[0087] In this embodiment, first, a substrate layer 13 is formed. The substrate layer 13 can be made of glass or polyimide film material. The substrate layer 13 has good mechanical strength to facilitate the formation of other structural components on the substrate layer 13, and to facilitate the stable connection of the ultrasonic fingerprint film 100 with the housing of the electronic device or the back of the display screen of the electronic device. The length and width of the substrate layer 13 can be manufactured according to the required length and width design dimensions of the ultrasonic fingerprint module 100, so that the length and width dimensions of the manufactured ultrasonic fingerprint module 100 meet the specification requirements.

[0088] Then, a pixel electrode layer is formed on the substrate layer 13. The pixel electrode layer is composed of a plurality of pixel electrodes 14. The length and width of the pixel electrode layer are substantially the same as those of the substrate layer 13. The plurality of pixel electrodes 14 of the pixel electrode layer can be formed on the substrate layer 13 by a TFT printing process. The material of the pixel electrode 14 is any one of indium tin oxide (ITO), nano silver wire (Agnanowire), metal mesh, nano carbon tube and graphene. The pixel electrode 14 made of the above materials has good toughness and light transmittance.

[0089] Then, a piezoelectric layer 15 is formed on the pixel electrode layer. The length and width of the piezoelectric layer 15 are roughly the same as those of the pixel electrode layer. The piezoelectric layer 15 covers the multiple pixel electrodes 14. The piezoelectric layer 15 is a sheet structure made of piezoelectric material. The shape of the piezoelectric layer 15 matches the shape of the substrate layer 13. The material of the piezoelectric layer 15 is polyvinylidene fluoride (PVDF). Since polyvinylidene fluoride has good toughness and light transmittance, the piezoelectric layer 15 has good flexibility and light transmittance, which ensures the flexibility and light transmittance of the ultrasonic fingerprint module 100.

[0090] Then, a conductive electrode 16 is formed on the piezoelectric layer 15. The length and width of the conductive electrode 16 are the same as those of the pixel electrode layer, so that the conductive electrode 16 matches the pixel electrode layer. The conductive electrode 16 can be formed on the piezoelectric layer 15 by a screen printing process. The conductive electrode 16 is an integral layered structure made of a conductive material. The shape of the conductive electrode 16 matches the shape of the piezoelectric layer 15. The conductive electrode 16 can be made of silver material. The conductive electrode 16 can be formed after the silver paste is cured. Two or more layers of the conductive electrode 16 can be formed on the piezoelectric layer 15, so that the surface roughness of the outermost conductive electrode 16 away from the piezoelectric layer 15 is smaller, that is, the bottom surface of the detection layer of the ultrasonic detection layer 10 is smoother.

[0091] 102: Provide a liquid ink material containing a resin material and carbon powder particles.

[0092] In this embodiment, the resin material can be any one of acrylic resin, polyester resin, isocyanate resin, phenolic resin, epoxy resin or a combination of multiple resin materials. As a preferred embodiment, the liquid ink material is formed by mixing epoxy resin and carbon powder particles.

[0093] Furthermore, the liquid ink material also contains a defoamer and a leveling agent, that is, epoxy resin, carbon powder particles, a defoamer and a leveling agent are mixed and stirred to form the liquid ink material.

[0094] By including a defoamer in the liquid ink material, the number of bubbles in the ink layer 20 can be effectively reduced, and the reflection efficiency of the ink layer 20 to ultrasound can be improved. The defoamer can be modified dimethyl silane, or polyoxypropylene oxyethylene glycerol ether, or a mixed defoamer of modified dimethyl silane and polyoxypropylene oxyethylene glycerol ether. The mass proportion of the defoamer is 1.0% to 3.0%. As a preferred embodiment, the mass proportion of the defoamer is 1.5% to 2.5%. When the mass proportion of the defoamer is 1.5%, the liquid ink material can have a small amount of bubbles after stirring, and the ink layer 20 formed after the liquid ink material is solidified also has a small amount of bubbles, and the ultrasonic fingerprint module 100 meets the fingerprint recognition requirements. When the mass proportion of the defoamer is 2.5%, the bubbles in the liquid ink material after stirring can be effectively eliminated, and the ink layer 20 formed after the liquid ink material is solidified can also contain no bubbles. The ultrasonic fingerprint module 100 provided with the ink layer 20 has excellent performance and high fingerprint recognition efficiency.

[0095] By including a leveling agent in the liquid ink material, the surface roughness of the ink layer 20 can be effectively reduced, and the reflection efficiency of the ink layer 20 to ultrasound can be improved. The leveling agent can be a fluorocarbon organic modified siloxane, or a polyether siloxane copolymer, or a mixed leveling agent of a fluorocarbon organic modified siloxane and a polyether siloxane copolymer. The mass proportion of the leveling agent is 0.2% to 1.5%. As a preferred embodiment, the mass proportion of the leveling agent is 0.5% to 1.0%. When the mass proportion of the leveling agent is 0.5%, the surface of the ink layer 20 formed after the liquid ink material is cured is smooth, and the surface roughness of the ink layer 20 can be controlled at 0.6Rz / μm. When the mass proportion of the leveling agent is 1.0%, the surface roughness of the ink layer 20 formed after the liquid ink material is cured can be controlled at 0.4Rz / μm, so that the ultrasonic recognition efficiency of the ultrasonic fingerprint module 100 is effectively improved.

[0096] 103 : Laying the liquid ink material on the bottom surface of the detection layer of the ultrasonic detection layer 10 , and forming an ink layer 20 after the liquid ink material is solidified, wherein the ink layer 20 covers the ultrasonic receiving surface of the ultrasonic detection layer 10 .

[0097] In this embodiment, the outermost conductive electrode 16 away from the surface of the piezoelectric layer 15 forms the bottom surface of the detection layer of the ultrasonic detection layer 10. The liquid ink material can be formed on the conductive electrode 16 by vacuum evaporation, screen printing, spraying, sputtering or other processes.

[0098] In another embodiment, the length and width of the substrate layer 13 can be processed according to at least n times the length and width design dimensions of the required ultrasonic fingerprint module 100, so that after the large-area pixel electrode layer 14, piezoelectric layer 15, conductive electrode 16 and ink layer 20 are sequentially formed on the substrate layer 13, multiple ultrasonic fingerprint modules 100 can be obtained in batches through cutting. The pixel electrode layer 15, piezoelectric layer 15, conductive electrode 16 and ink layer 20 can be processed and formed according to multiple preset ultrasonic fingerprint module 100 array arrangement areas to reduce the production cost of obtaining multiple ultrasonic fingerprint modules 100 in batches.

[0099] See also Figure 5 The present application also provides a display screen assembly 200, which includes a display screen 210 and the ultrasonic fingerprint module 100. The display screen 210 has an outer surface 211 facing the user, the ultrasonic fingerprint module 100 is fixed inside or under the display screen 210, and the ink layer 20 is away from the outer surface 211 relative to the ultrasonic detection layer 10.

[0100] See also Figure 6 In one embodiment, the ink layer 20 of the ultrasonic fingerprint module 100 is not transparent to visible light. The ultrasonic fingerprint module 100 is fixed under the display screen 210, and the ink layer 20 blocks the display light of the display screen 210 from being emitted from the side away from the outer surface 211.

[0101] Specifically, the display screen 210 is provided with an organic electroluminescent layer 212, and the ultrasonic detection layer 10 is stacked on a side of the organic electroluminescent layer 212 away from the outer surface 211. The display screen 210 is provided with a glass cover plate 213. The outer surface 211 is arranged on the glass cover plate 213. The organic electroluminescent layer 212 is attached to the glass cover plate 213. The substrate layer 13 of the ultrasonic detection layer 10 is attached to the organic electroluminescent layer 212. The substrate layer 13 can constitute the base layer of the organic electroluminescent layer 212. The substrate layer 13 can be attached to the organic electroluminescent layer 212 via a glue layer. The display screen 210 is an OLED (Organic Light-Emitting Diode) display screen 210. By utilizing the light-proof performance of the ink layer 20 of the ultrasonic fingerprint module 100, the ink layer 20 can form the backplane of the display screen 210, so that the display screen 210 can display images. The display screen 210 can be a flexible display screen. The ultrasonic fingerprint module 100 can be bent and deformed along with the display screen 210 .

[0102] It can be understood that, by setting the distance from the side of the fingerprint detection layer 10 that is in contact with the ink layer 20 to the outer surface 211, and setting the ultrasonic frequency emitted by the ultrasonic detection layer 10, the piezoelectric layer 15 of the ultrasonic detection layer 10 emits a first ultrasonic signal 01 toward the outer surface 211, and emits a second ultrasonic signal 02 toward the ink layer 20. The second ultrasonic signal 02 is reflected by the interface where the ink layer 20 contacts the air to form a third ultrasonic signal 03. The third ultrasonic signal 03 is also emitted toward the outer surface 211. The third ultrasonic signal 03 and the first ultrasonic signal 01 can form a resonance, and are emitted toward the outer surface 211 together to enhance the fingerprint recognition efficiency.

[0103] After testing, six display screen assemblies 200 are provided, and the thickness of the ink layer 20 in the six display screen assemblies 200 is different from each other, and the SNR values ​​and the obtained fingerprint image resolution (LPMM) values ​​of the ultrasonic fingerprint module 100 in the six display screen assemblies 200 are compared. For example, the thickness of the ink layer 20 in the six display screen assemblies 200 is 5μm, 10μm, 15μm, 20μm, 25μm, and 30μm, respectively. After testing, the SNR values ​​of the ultrasonic fingerprint module 100 in the six display screen assemblies 200 are 4.571, 4.9, 5.308, 5.859, 6.105, and 5.72, respectively, and the fingerprint image resolution (LPMM) values ​​obtained by the ultrasonic fingerprint module 100 in the six display screen assemblies 200 are 3.23, 3.32, 3.421, 3.594, 3.593, and 3.6, respectively. It can be seen that when the thickness of the ink layer 20 is 25 μm, the performance of the ultrasonic fingerprint module 100 of the display assembly 200 is excellent. That is, as a preferred embodiment, the thickness of the ink layer 20 of the ultrasonic fingerprint module 100 can be set to 20 μm to 30 μm.

[0104] See also Figure 7 and Figure 8 , in another embodiment, with Figure 6The embodiments shown are substantially the same, except that the display screen 210 is provided with a liquid crystal panel 214 and a backlight module 215, the backlight module 215 includes a backlight guide plate 216 attached to the liquid crystal panel 214 and a backlight source 217 fixed to the side of the backlight guide plate 216, and the ultrasonic detection layer 10 is attached to the side of the backlight guide plate 216 away from the liquid crystal panel 214. The liquid crystal panel 214 is attached to the glass cover plate 213. The substrate layer 13 is attached to the backlight guide plate 216. The substrate layer 13 can constitute the base layer of the backlight guide plate 216. Due to the opacity of the ink layer 20, the ink layer 20 can constitute the backplane of the backlight module 215, so that the liquid crystal panel 214 obtains the light of the backlight module 215, thereby realizing the display of images. In order to increase the structural stability of the backlight module 215, the backlight module 215 also includes a packaging base plate 218, which packages the backlight source 217 and the backlight guide plate 216, and the ultrasonic fingerprint module 100 is fixed between the backlight guide plate 216 and the packaging base plate 218. The packaging base plate 218 protects the ultrasonic fingerprint module 100, and the packaging base plate 218 also packages the backlight source 217 to prevent the backlight source 217 from leaking light. The packaging base plate 218 can be a bendable metal plate. There is an assembly gap between the packaging base plate 218 and the ultrasonic fingerprint module 100 to increase the ultrasonic wave blocking rate of the ink layer 20 and ensure the effectiveness of the ultrasonic fingerprint module 100 in identifying fingerprints.

[0105] See also Fig. 9 , in another embodiment, with Figure 6 The embodiments shown are substantially the same, except that the ultrasonic fingerprint module 100 can be embedded in the display screen 210, and the ultrasonic fingerprint module 100 is located in the non-display area of ​​the display screen 210. Specifically, the glass cover plate 213 has a non-light-transmitting area 2131. The non-light-transmitting area 2131 of the glass cover plate 213 is composed of an ink layer attached to the glass. The non-light-transmitting area 2131 of the glass cover plate 213 covers the ultrasonic fingerprint module 100 to ensure the appearance performance of the display screen 210 assembly 200. The ultrasonic fingerprint module 100 is set in the non-display area of ​​the display screen 210 assembly 200 to avoid the ink layer 20 of the ultrasonic fingerprint module 100 blocking the display light, so as to ensure the display effect of the display area of ​​the display screen 210 assembly 200. There is a gap between the ink layer 20 of the ultrasonic fingerprint module 100 and other layer structures of the display screen 210 assembly 200 to ensure the ultrasonic wave blocking efficiency of the ink layer 20 and ensure the fingerprint recognition effectiveness of the ultrasonic fingerprint module 100.

[0106] See also Fig.10 , in another embodiment, with Figure 7 The embodiments shown are substantially the same, except that the display screen 210 is provided with a substrate 2101 bonded to the organic electroluminescent layer 212, the ultrasonic detection layer 10 includes a plurality of pixel electrodes 14, a piezoelectric layer 15 and a conductive electrode 16, the plurality of pixel electrodes 14 are arrayed on a side of the substrate 2101 away from the glass cover 213, the piezoelectric layer 15 covers the plurality of pixel electrodes 14, the conductive electrode 16 is stacked on a side of the piezoelectric layer 15 away from the plurality of pixel electrodes 14, and the ink layer 20 is printed and formed on a side of the conductive electrode 16 away from the piezoelectric layer 15. That is, the ultrasonic fingerprint module 100 is attached to the substrate 2101 of the display screen 210. Of course, in other embodiments, the display screen 210 is provided with a substrate 2101 of a liquid crystal panel 214, and the plurality of pixel electrodes 14 of the ultrasonic fingerprint module 100 can be formed on the substrate 2101 of the liquid crystal panel 214.

[0107] See also Fig.11 The present application also provides an electronic device 300, the electronic device 300 includes the display screen assembly 200, and the electronic device 300 also includes a back cover 310 and a main board 320. The display screen 210 is covered with the back cover 310. The main board 320 is fixed between the back cover 310 and the display screen 210, and the main board 320 is electrically connected to the display screen 210 and the ultrasonic fingerprint module 100. The main board 320 can receive the electrical signal of the ultrasonic fingerprint module 100 to identify the user's fingerprint image. It can be understood that the ultrasonic fingerprint module 100 can receive a fingerprint detection signal detected by the user's fingerprint, and the fingerprint detection signal detected by the user's fingerprint can be an initial detection signal transmitted from the ultrasonic fingerprint module 100 to the user's fingerprint, or an initial detection signal transmitted from an external ultrasonic signal source to the user's fingerprint. The electronic device 300 can be a mobile phone, a tablet computer, a laptop computer, a media player and other devices, or it can be a financial terminal device such as an automated teller machine (ATM). The electronic device 300 is configured with the ultrasonic fingerprint module 100 in the display screen 210 , so that the electronic device 300 can meet various fingerprint recognition requirements and improve fingerprint recognition efficiency.

[0108] It can be understood that any specific numerical value with protective significance in this embodiment is not limited to the specific numerical value provided above, and other numerical values ​​similar to the specific numerical values ​​provided in this embodiment are also within the protection scope of the embodiment of this application.

[0109] The above is a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the principle of the present invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. An ultrasonic fingerprint module, characterized in that: The ultrasonic fingerprint module includes an ultrasonic detection layer and an ink layer, the ultrasonic detection layer has an ultrasonic receiving surface, the ink layer is arranged on a side of the ultrasonic detection layer away from the ultrasonic receiving surface, the ink layer is used to reflect the ultrasonic wave emitted from the ultrasonic detection layer, the ink layer contains resin material and carbon powder particles, the carbon powder particles fill the gaps between resin particles in the resin material, the average particle size of the carbon powder particles is 0.5 microns to 5 microns, and the mass proportion of the carbon powder particles is 2.5% to 15%.

2. The ultrasonic fingerprint module according to claim 1, characterized in that: The average particle size of the carbon powder particles is 0.8 microns to 2 microns.

3. The ultrasonic fingerprint module according to claim 2, characterized in that: The average particle size of the carbon powder particles is 1.0 micron.

4. The ultrasonic fingerprint module according to claim 1, characterized in that: The carbon powder particles account for 3.0% to 10% of the ink layer by mass.

5. The ultrasonic fingerprint module according to claim 4, characterized in that: The carbon powder particles account for 5% by mass of the ink layer.

6. The ultrasonic fingerprint module according to claim 1, characterized in that: The resin material includes any one of acrylic resin, polyester resin, isocyanate resin, phenolic resin, and epoxy resin, or a combination of multiple resin materials.

7. The ultrasonic fingerprint module according to claim 6, characterized in that: The resin material is an epoxy resin with a CAS number of 38891-59-7.

8. The ultrasonic fingerprint module according to claim 1, characterized in that: The ink layer is provided with a leveling agent, and the leveling agent is used to improve the surface leveling of the ink layer during the production process and to improve the surface leveling of the ink layer finally formed.

9. The ultrasonic fingerprint module according to claim 1, characterized in that: The ink layer is provided with a defoaming agent, and the defoaming agent is used to eliminate bubbles in the ink layer during the production process and eliminate bubbles in the ink layer finally formed.

10. The ultrasonic fingerprint module according to any one of claims 1 to 9, characterized in that: The ultrasonic detection layer comprises a substrate layer, a pixel electrode layer, a piezoelectric layer and a conductive electrode which are stacked in sequence, and the ink layer is arranged on a side of the conductive electrode away from the piezoelectric layer.

11. The ultrasonic fingerprint module according to any one of claims 1 to 9, characterized in that: The thickness of the ink layer is 5 micrometers to 30 micrometers.

12. The ultrasonic fingerprint module according to claim 11, characterized in that: The thickness of the ink layer is 20 micrometers to 30 micrometers.

13. The ultrasonic fingerprint module according to claim 12, characterized in that: The thickness of the ink layer is 25 microns.

14. A method for manufacturing an ultrasonic fingerprint module, characterized in that: The method for manufacturing the ultrasonic fingerprint module comprises the following steps: Providing an ultrasonic detection layer, the ultrasonic detection layer having an ultrasonic receiving surface and a detection layer bottom surface disposed opposite to the ultrasonic receiving surface; A liquid ink material containing carbon powder particles and a resin material is provided, wherein the carbon powder particles fill the gaps between the resin particles in the resin material, the average particle size of the carbon powder particles is 0.5 micrometers to 5 micrometers, and the carbon powder particles account for 2.5% to 15% of the mass of the liquid ink material; The liquid ink material is laid on the bottom surface of the detection layer, and an ink layer is formed after the liquid ink material is solidified, and the ink layer covers the ultrasonic wave receiving surface of the ultrasonic wave detection layer.

15. The method for manufacturing an ultrasonic fingerprint module according to claim 14, characterized in that: The liquid ink material also contains a leveling agent and a defoaming agent. The resin material, carbon powder particles, the leveling agent and the defoaming agent are mixed and stirred to form the liquid ink material.

16. The method for manufacturing an ultrasonic fingerprint module according to claim 14, characterized in that: In the step of providing the ultrasonic detection layer, a substrate layer, a pixel electrode, a piezoelectric layer and a conductive electrode are sequentially formed and stacked, and the bottom surface of the detection layer is formed on a side of the conductive electrode away from the piezoelectric layer.

17. An electronic device, characterized in that: The electronic device comprises the ultrasonic fingerprint module according to any one of claims 1 to 13.

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