Ultrathin high-shading polyimide composite film and low-temperature laminating process thereof

Abstract

The invention discloses an ultrathin high-shading polyimide composite film and a low-temperature laminating process thereof, and relates to the technical field of polyimide film material preparation. The polyimide composite film comprises a transparent polyimide substrate layer, a shading layer and an anti-reflection layer, the shading layer is arranged between the transparent polyimide base material layer and the anti-reflection layer; the shading layer comprises a nano carbon material composite system and fluorine-containing resin. The invention also provides a low-temperature preparation process of the composite film and a low-temperature pressing process applied to a camera module, the pressing temperature is as low as 80 DEG C, and the problem of thermal deformation of the lens module is effectively avoided; the prepared composite film has the advantages of being ultrathin, high in shading, low in dielectric, resistant to bending and the like, and is particularly suitable for a miniature camera module with extremely high requirements for thickness and reliability.

Description

TECHNICAL FIELD

[0001] The application provides an ultrathin high-shading polyimide composite film and a low-temperature pressing process thereof, and relates to the technical field of polyimide film material preparation. BACKGROUND

[0002] With the rapid iteration of consumer electronics and intelligent vehicles, smartphones are developing towards multi-camera and high-pixel, and autonomous driving relies on high-definition imaging systems integrating surround-view cameras and laser radars to realize obstacle recognition and lane detection. These scenarios have strict requirements for the imaging quality of miniature camera modules, which not only need to ensure low noise and high contrast, but also need to avoid stray light crosstalk between the lens and the CMOS image sensor, and light interference caused by the driving circuit and signal transmission line around the sensor. The key to solving this problem is to use a material with ultra-thin thickness and high light shielding property inside the module. In traditional solutions, black polyimide film and metal foil are the mainstream choices, but both have obvious limitations. Black PI film has good temperature resistance and insulation, but to achieve the extreme light shielding property required by the module (transmittance <0.1%, and low transmittance needs to be maintained in the full visible light band 400-760 nm and the near-infrared supplementary light band 760-1100 nm), the thickness usually needs to exceed 5 μm, and some high light shielding models even reach 8-10 μm. However, current miniature camera modules are developing towards ultra-thin, and the thick PI film will occupy valuable internal space, which is contrary to this trend. More importantly, during the high-temperature compression process of module assembly, the thermal expansion coefficient of black PI film is about 20 ppm / ℃, while the thermal expansion coefficients of aluminum alloy or engineering plastic commonly used in lens seats are 23 ppm / ℃ and 30 ppm / ℃ respectively. The mismatch of thermal expansion coefficients between the two materials can easily cause stress deformation of the lens seat, which in turn changes the relative position accuracy of the lens and the sensor, affects the accuracy of the autofocus function, and causes imaging blur or focus offset. Although metal foil can achieve low transmittance with thinner thickness, it has two major defects: first, it is easy to bend in terms of physical properties, and slight stress during precise module assembly can cause wrinkles or deformation, which can damage the sealing of the light shielding layer and cause local light leakage. Second, the dielectric constant is too high, such as the dielectric constant of pure copper foil is about 10, while the CMOS sensor peripheral circuit requires a material with a dielectric constant less than 3 to reduce capacitive interference. A high dielectric constant can cause noise in the transmission of sensor electrical signals, affecting the stability of image data reading, and even causing pixel point abnormalities. In addition, the preparation process of existing light shielding films also has obvious shortcomings. Whether it is the high-temperature imidization process of black PI film or the high-temperature compression process of metal foil and substrate, the operating temperature is close to or even exceeds the glass transition temperature of some plastic lens materials. For example, the glass transition temperature of commonly used PMMA lens is about 105℃, and the glass transition temperature of PC lens is about 150℃. Even the heat-resistant cyclo olefin polymer lens has a glass transition temperature of only 170℃. High-temperature environment can cause irreversible thermal deformation of the lens, such as changes in lens curvature and surface flatness, which can cause imaging distortion. In the autonomous driving scenario, this distortion may increase the error in obstacle distance judgment, which seriously threatens road safety.Therefore, the industry urgently needs a new composite film material and new process which can achieve extreme light shielding, low dielectric constant and integration with module through low-temperature process under ultra-thin total thickness. SUMMARY

[0003] To solve the above problems, the present application provides an ultra-thin high light shielding polyimide composite film, comprising a transparent polyimide substrate layer, a light shielding layer and an anti-reflection layer; the light shielding layer is arranged between the transparent polyimide substrate layer and the anti-reflection layer; the light shielding layer comprises a nano-carbon material composite system and a fluorine-containing resin.

[0004] Preferably, the thickness of the transparent polyimide substrate layer is 4-6 μm, and the light transmittance at a wavelength of 550 nm is greater than 90%.

[0005] Preferably, the thickness of the light shielding layer is 2-4 μm, and the light transmittance at a wavelength of 550 nm is less than 0.05%.

[0006] Preferably, the thickness of the anti-reflection layer is 0.4-0.6 μm.

[0007] Preferably, the nano-carbon material composite system is composed of nano-graphene and carbon black; the addition amount of the nano-graphene is 8-12 parts, and the addition amount of the carbon black is 5 parts, based on 100 parts of the total mass of the solid of the light shielding layer.

[0008] Preferably, the flake diameter of the nano-graphene is 1-5 μm, and the number of layers is 5-10 layers.

[0009] Preferably, the addition amount of the fluorine-containing resin is 15 parts, based on 100 parts of the total mass of the solid of the light shielding layer; the fluorine-containing resin is one or more of soluble polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer and polyvinylidene fluoride.

[0010] Preferably, the light shielding layer further comprises a polyimide precursor resin; the polyimide precursor resin is a polyamide acid solution, and the solid content is 15-25%, and the viscosity range is 3000-5000 cP.

[0011] Preferably, the anti-reflection layer is one or both of magnesium fluoride and silicon dioxide formed by vacuum evaporation.

[0012] The present application also provides a preparation method of the above-mentioned ultra-thin high light shielding polyimide composite film, comprising the following steps: S1. providing a transparent polyimide substrate; S2. coating a light shielding layer slurry on one side of the transparent polyimide substrate, and forming a light shielding layer through low-temperature baking; S3. preparing an anti-reflection layer on the light shielding layer by physical vapor deposition.

[0013] Preferably, the preparation method of the light-shielding layer slurry in step S2 is: dispersing nano-graphene, carbon black and fluorine-containing resin powder in N-methyl pyrrolidone solvent under high-speed stirring to form a first dispersion liquid; mixing the first dispersion liquid with a polyamide acid solution in proportion, and treating by planetary stirring and ball milling to obtain a uniform light-shielding layer slurry; the solid content of the light-shielding layer slurry is controlled at 25%-35%, and the viscosity is controlled at 2000-4000 cP.

[0014] Preferably, the coating in step S2 adopts micro-gravure coating mode, the coating speed is 5-15 m / min, and the coating gap is 50-100 μm.

[0015] Preferably, the low-temperature baking in step S2 is at a temperature of 70-90 ℃, and the baking time is 5-15 minutes.

[0016] Preferably, the physical vapor deposition method in step S3 is vacuum evaporation, and the vacuum degree is required to be less than 5.0×10 -3 Pa, and the evaporation rate is 0.5-2.0 nm / s.

[0017] The application also provides a low-temperature pressing process of the above-mentioned ultra-thin high-light-shielding polyimide composite film, and relates to an application method of the ultra-thin high-light-shielding polyimide composite film in a camera module, which comprises: fixing the composite film by low-temperature pressing through an adhesive with a lens barrel or a sensor substrate in a direction of the transparent polyimide base material layer of the composite film towards an image sensor; the process conditions of the low-temperature pressing fixation are: the pressing temperature is 70-90 ℃, the pressing pressure is 0.5-1.5 MPa, and the pressing time is 10-30 seconds; and the adhesive is an ultraviolet curing type or a thermal curing type acrylate adhesive, and the thickness of the adhesive is 10-30 μm.

[0018] The application has the following beneficial effects:

[0019] The ultrathin high-shading polyimide composite film and its low-temperature pressing process provided by the application realize multiple excellent performances through the design of an asymmetric three-layer structure, the complex shading system of nanometer graphene and carbon black, and the introduction of fluorine-containing resin. First, the composite film realizes an extreme shading effect with a shading layer light transmittance of less than 0.05% at a wavelength of 550 nm under a total thickness of only 8.5 μm, while the substrate layer maintains a high light transmittance of more than 90%, meeting the lens light transmission requirement. Second, the specific nanometer carbon material complex system in the shading layer realizes complete shading at an extremely thin thickness of only 3 μm, breaking through the technical bottleneck that traditional carbon black filling materials are difficult to achieve this effect in a thin layer. Third, the addition of 15 parts of fluorine-containing resin effectively controls the dielectric constant of the shading layer to be below 2.8, significantly reducing the interference of the shading layer on the electrical signal of the image sensor. Most importantly, the 80℃ low-temperature pressing process matched with the application completely avoids the thermal deformation problem of the plastic lens module caused by the traditional high-temperature process (> 150℃), ensuring the imaging quality and yield of the camera. In summary, the application perfectly balances the characteristics of ultrathin, high shading, low dielectric, and low-temperature processing, effectively solving the key technical problems in the manufacturing of miniature camera modules. DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments of the application will be clearly and completely described below with reference to the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, and not all embodiments. Based on the embodiments in the application, all other embodiments obtained by a person of ordinary skill in the art without creative labor belong to the scope of protection of the application.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. In addition, any method and material similar or equivalent to those described herein can be used in the application. The preferred implementation methods and materials described herein are only for demonstration, but cannot limit the content of the application.

[0022] The experimental methods in the following examples are all conventional methods unless otherwise specified. The test materials used in the following examples are all purchased from commercial channels unless otherwise specified.

[0023] Example 1

[0024] A transparent polyimide film with a thickness of 5 μm and a light transmittance of 92% (Japan Ubukogoseika Co., Ltd., UPILEX-10S) was prepared as a substrate; a shading layer slurry was prepared: 10 parts of nanometer graphene powder with a flake diameter of 1-3 μm and a layer number of 5-8 layers (Changzhou Sixth Element Material Technology Co., Ltd., SE1230), 5 parts of conductive carbon black powder, and 15 parts of soluble polytetrafluoroethylene powder (Japan Daikin Industry Co., Ltd., )In a beaker, 3 times of N-methyl pyrrolidone solvent (BASF) by weight of total solid was added and stirred for 30 minutes at 2000 rpm using a high speed disperser to obtain a first dispersion. 100 parts of a polyamic acid solution (Japan Ube Industries Co., Ltd., U-Varnish-S) with a solid content of 18% and a viscosity of 4000 cP was slowly added into the first dispersion under stirring. After mixing, a planetary stirrer was used to stir for 2 hours at 500 rpm. Finally, the mixture was transferred into a ball mill tank with zirconium oxide balls as the grinding medium and ball-milled for 4 hours to obtain a uniform and fine light-shielding layer slurry with a solid content of 30% and a viscosity of 3500 cP. The slurry was coated on a transparent PI substrate using a micro-gravure coater with a coating speed of 10 m / min and a coating gap of 80 μm. The coated film was sent into an oven at 80°C for 10 minutes to evaporate the solvent and to be initially cured to form a light-shielding layer with a thickness of 3 μm. The film with the light-shielding layer was placed in a vacuum evaporation machine, and the chamber was evacuated to a pressure lower than 3.0 x 10-3 Pa. High purity silicon dioxide particles were used as the evaporation source and heated by an electron beam. The silicon dioxide particles were evaporated at a rate of 1.0 nm / s until a 0.5 μm thick silicon dioxide anti-reflective layer was formed on the surface of the light-shielding layer to obtain the ultra-thin high light-shielding polyimide composite film. The composite film was applied in a mobile phone camera module: a layer of 20 μm thick ultraviolet curing acrylic adhesive (DeXia) was applied around the periphery of the image sensor substrate, and the composite film was attached to the sensor with the transparent PI substrate layer facing the sensor. A pressing device was used to press and fix the composite film at a temperature of 80°C and a pressure of 1.0 MPa for 20 seconds. Finally, the adhesive was completely cured by ultraviolet irradiation for 10 seconds.

[0025] Example 2

[0026] A transparent polyimide film with a thickness of 4 μm and a light transmittance of 93.1% was prepared as a substrate; an opaque layer slurry was prepared: 8 parts of a nano-graphene powder with a flake diameter of 2-4 μm and a number of layers of 6-9, 5 parts of a conductive carbon black powder, and 15 parts of a tetrafluoroethylene-hexafluoropropylene copolymer powder were accurately weighed into a beaker, a solvent of N-methyl pyrrolidone was added in an amount of 3 times the total mass of the solids, and the mixture was stirred for 35 minutes at a high speed of 1800 rpm using a high-speed disperser to obtain a first dispersion liquid; 100 parts of a polyamide acid solution with a solid content of 20% and a viscosity of 3500 cP was stirred, and the first dispersion liquid was slowly added thereto, and after mixing, a planetary stirrer was used to stir the mixture at 450 rpm for 2.5 hours, and finally the mixture was transferred into a ball mill tank, zirconium oxide balls were used as the grinding medium, and the mixture was ball milled for 4.5 hours to obtain a uniform and fine opaque layer slurry, and the solid content and viscosity of the slurry were measured to be 28% and 3000 cP, respectively; the slurry was coated on the transparent PI substrate using a micro-gravure coater, the coating speed was set to 8 m / min, and the coating gap was set to 60 μm; the coated film was sent into an oven at 70°C, and baked for 15 minutes to allow the solvent to fully volatilize and to be initially cured, thereby forming an opaque layer with a thickness of 2.5 μm; the film with the opaque layer was placed in a vacuum evaporation machine, the chamber was vacuumed to a pressure of less than 4.0 x 10-3 Pa, a magnesium fluoride source was heated using a resistance-heated boat, and the magnesium fluoride was evaporated at a rate of 0.8 nm / s until a magnesium fluoride anti-reflective layer with a thickness of 0.4 μm was formed on the surface of the opaque layer, thereby obtaining the ultra-thin high-opaque polyimide composite film. The composite film was applied to a mobile phone camera module: a layer of an ultraviolet-curable acrylic adhesive with a thickness of 15 μm was applied around the periphery of the image sensor substrate, the composite film was attached to the sensor with the transparent PI substrate layer facing the sensor, a pressing device was used to press and fix the composite film at a temperature of 70°C and a pressure of 0.5 MPa for 30 seconds, and finally the adhesive was completely cured by irradiation with ultraviolet light for 12 seconds.

[0027] Example 3

[0028] A transparent polyimide film with a thickness of 6 μm and a light transmittance of 91.8% was prepared as a substrate; an opaque layer slurry was prepared: 12 parts of nanographene powder with a flake diameter of 1-3 μm and a number of layers of 7-10, 5 parts of conductive carbon black powder, and 15 parts of polyvinylidene fluoride powder were accurately weighed into a beaker, 3 times the total mass of the solids of N-methyl pyrrolidone solvent was added, and stirred for 25 minutes at 2200 rpm on a high-speed disperser to obtain a first dispersion liquid; 100 parts of a polyamic acid solution with a solid content of 22% and a viscosity of 4500 cP was slowly added under stirring, and after mixing, a planetary stirrer was used to stir at 550 rpm for 1.5 hours, and finally transferred into a ball mill tank, with zirconia balls as the grinding medium, and ball-milled for 3.5 hours to obtain a uniform and fine opaque layer slurry, and the solid content was measured to be 32%, and the viscosity was 3800 cP; the above slurry was coated on the transparent PI substrate using a micro-gravure coater, the coating speed was set to 12 m / min, and the coating gap was set to 90 μm; the coated film was sent into a 90°C oven, baked for 5 minutes to fully volatilize the solvent and preliminarily solidify, forming an opaque layer with a thickness of 3.5 μm; the film with the opaque layer was placed in a vacuum evaporation machine, the chamber was vacuumed to a pressure below 2.5 x 10-3 Pa, two independent electron beam evaporation sources were used to evaporate silicon dioxide at a rate of 1.2 nm / s and magnesium fluoride at a rate of 0.8 nm / s, and by controlling the rate and time, a composite anti-reflective layer of silicon dioxide and magnesium fluoride with a total thickness of 0.6 μm was formed on the surface of the opaque layer, thereby obtaining the ultra-thin high-opaque polyimide composite film. The composite film was applied to a mobile phone camera module: a layer of thermosetting acrylate adhesive with a thickness of 25 μm was applied around the periphery of the image sensor substrate, the composite film was attached to the sensor with its transparent PI substrate layer facing the sensor, and a pressing device was used to press and fix at a temperature of 90°C and a pressure of 1.5 MPa for 10 seconds to preliminarily fix and simultaneously cure the adhesive.

[0029] Comparative Example 1

[0030] A transparent polyimide film with a thickness of 5 μm and a light transmittance of 92.5% was prepared as a substrate; an opaque layer slurry was prepared: 15 parts of conductive carbon black powder (without adding nano-graphene) and 15 parts of polytetrafluoroethylene powder were accurately weighed into a beaker, 3 times the total mass of the solids of N-methyl pyrrolidone solvent was added, and stirred for 30 minutes at 2000 rpm on a high-speed disperser to obtain a first dispersion liquid; 100 parts of a polyamide acid solution with a solid content of 18% and a viscosity of 4000 cP was slowly added to the first dispersion liquid under stirring, and after mixing, a planetary stirrer was used to stir for 2 hours at 500 rpm, and finally transferred to a ball mill tank, with zirconia balls as the grinding medium, and ball milled for 4 hours to obtain a uniform opaque layer slurry, the solid content of which was measured to be 30%, and the viscosity was 3400 cP; the above slurry was coated on the transparent PI substrate using a micro-gravure coater, the coating speed was set to 10 m / min, and the coating gap was set to 80 μm; the coated film was sent into an oven at 80°C for 10 minutes to allow the solvent to fully evaporate and to be initially cured, forming an opaque layer with a thickness of 3 μm; the film with the opaque layer was placed in a vacuum evaporation machine, the chamber was evacuated to a pressure below 3.0 x 10-3 Pa, the silicon dioxide source was heated by an electron beam, and was evaporated at a rate of 1.0 nm / s until a 0.5 μm thick silicon dioxide anti-reflective layer was formed on the surface of the opaque layer, thereby obtaining a composite film. The composite film was applied to a mobile phone camera module: a layer of ultraviolet-curable acrylic adhesive with a thickness of 20 μm was applied around the periphery of the image sensor substrate, the composite film was attached to the sensor with its transparent PI substrate layer facing the sensor, a pressing device was used to press and fix it at a temperature of 80°C and a pressure of 1.0 MPa for 20 seconds, and finally the adhesive was completely cured by ultraviolet irradiation for 10 seconds.

[0031] Comparative Example 2

[0032] A transparent polyimide film with a thickness of 5 μm and a light transmittance of 92.5% was prepared as a base material; an opaque layer slurry was prepared: 10 parts of nanographene powder with a flake diameter of 1-3 μm and a number of layers of 5-8 and 5 parts of conductive carbon black powder (without adding fluorine-containing resin) were accurately weighed in a beaker, 3 times the total mass of the solids of N-methyl pyrrolidone solvent was added, and stirring was performed at 2000 rpm for 30 minutes in a high-speed dispersion machine to obtain a first dispersion liquid; 115 parts of a polyamic acid solution with a solid content of 18% and a viscosity of 4000 cP was taken, and the first dispersion liquid was slowly added thereto under stirring, and after mixing, a planetary stirring machine was used to stir for 2 hours at 500 rpm, and finally, it was transferred into a ball mill tank, zirconium oxide balls were used as the grinding medium, and ball milling was performed for 4 hours to obtain a uniform opaque layer slurry, and the solid content was measured to be 30%, and the viscosity was 3600 cP; the above slurry was coated on the transparent PI base material using a micro-gravure coater, the coating speed was set to 10 m / min, and the coating gap was set to 80 μm; the coated film was sent into an oven at 80°C, and baking was performed for 10 minutes to fully volatilize the solvent and preliminarily cure, and an opaque layer with a thickness of 3 μm was formed; the film with the opaque layer was placed in a vacuum evaporation machine, the chamber pressure was reduced to less than 3.0 x 10-3 Pa, a silicon dioxide source was heated by an electron beam, and evaporation was performed at a rate of 1.0 nm / s until a silicon dioxide anti-reflection layer with a thickness of 0.5 μm was formed on the surface of the opaque layer, and a composite film was obtained. The composite film was applied to a mobile phone camera module: a layer of ultraviolet light-curable acrylic adhesive with a thickness of 20 μm was point-coated on the periphery of the image sensor substrate, the composite film was attached to the sensor with the transparent PI base material layer facing the sensor, a pressing device was used to press and fix at a temperature of 80°C and a pressure of 1.0 MPa for 20 seconds, and finally, the adhesive was completely cured by ultraviolet light irradiation for 10 seconds.

[0033] Comparative Example 3

[0034] The preparation process of the composite film was exactly the same as in Example 1, and a composite film with a total thickness of 8.5 μm was obtained. However, when the composite film was applied to a mobile phone camera module, the pressing process parameters were changed: a layer of ultraviolet light-curable acrylic adhesive with a thickness of 20 μm was point-coated on the periphery of the image sensor substrate, the composite film was attached to the sensor with the transparent PI base material layer facing the sensor, a pressing device was used to press and fix at a temperature of 160°C (traditional high temperature) and a pressure of 1.0 MPa for 20 seconds, and finally, the adhesive was completely cured by ultraviolet light irradiation for 10 seconds.

[0035] Comparative Example 4

[0036] A black polyimide film with a thickness of 10 μm purchased on the market (DuPont ). The commercial film was applied in a mobile phone camera module: a layer of 20 pm thick UV-curable acrylic adhesive was applied on the periphery of the image sensor substrate, and the commercial film was attached thereon (the film was a single layer structure without orientation distinction), a compression device was used to compress at a temperature of 160°C and a pressure of 1.0 MPa for 20 seconds for preliminary fixation, and finally the adhesive was completely cured by UV irradiation for 10 seconds.

[0037] The obtained product was detected by the following method, and the results are shown in Table 1.

[0038] Detection method:

[0039] Thickness: a contact film thickness gauge was used to measure the thickness of each sample at 10 random points, and the average value was taken to 0.1 pm.

[0040] Transmittance: an ultraviolet-visible spectrophotometer was used to fix the sample on the test light path, and the transmittance value (%) was directly read at a wavelength of 550 nm, and each sample was tested 3 times to take the average value.

[0041] Dielectric constant: an impedance analyzer was used to cut the sample into a specified size, and a circular aluminum electrode was made on the upper and lower surfaces by vacuum evaporation method, and the dielectric constant was calculated by measuring the capacitance value C and substituting the formula ε = (C*d) / (ε0*A), wherein d is the sample thickness, A is the electrode area, and ε0 is the vacuum dielectric constant (8.85 x 10-12 F / m). The test frequency was 1 MHz.

[0042] Lens distortion: an optical projector or laser displacement sensor was used to measure the change value of the flatness of the lens reference surface before and after the compression process, and the maximum value was taken as the distortion (pm).

[0043] Good product rate: 1000 camera modules were assembled on the simulated production line, and after completing all assembly and software debugging, the number of modules that passed the final imaging test (without black spots, glare, focusing misalignment, etc.) was counted, and the percentage was calculated.

[0044] Table 1 detection results

[0045]

[0046] It can be seen that the ultrathin high light shielding polyimide composite film prepared in embodiments 1-3 has a total thickness of only 6.9-10.1 μm, and the light shielding layer has a light transmittance of less than 0.05% at a wavelength of 550 nm, reaching an extremely light shielding level, which is far better than 0.35% of the single carbon black of comparative example 1 and 0.80% of the commercial product of comparative example 4, which fully proves that the synergistic effect is produced by the specific proportion of nanometer graphene and carbon black, and the light shielding performance far exceeds that of a single component at an extremely thin thickness; at the same time, the dielectric constant of the light shielding layer of the embodiments is stably below 2.8, which is significantly lower than that of comparative example 2 without adding fluorine-containing resin and commercial comparative example 4, which shows that the introduction of 15 parts of fluorine-containing resin plays a key role in reducing the dielectric constant and reducing signal interference; in terms of application performance, the lens distortion of the embodiments using low-temperature pressing at 80℃ is controlled within an extremely low range of 1.5 μm, and the module good product rate is as high as 99.3% or more, while the embodiments 1 using traditional high-temperature pressing at 160℃ and the commercial film of comparative example 4 have a huge distortion of more than 8.7 μm due to thermal deformation, and the good product rate drops to 88.9% and 85.7%, which irrefutably proves the creativity and necessity of the low-temperature pressing process of the present application at 80℃ for avoiding the deformation of heat-sensitive lens modules and ensuring high good product rate; in summary, the three-layer structure design, nanometer carbon material compounded light shielding system, fluorine-containing resin dielectric reduction modification and low-temperature pressing process of the present application are interrelated and jointly act, producing a synergistic effect of ultrathin, extremely light shielding, low dielectric and low-temperature processing compatibility, and solving the long-standing technical contradiction in the industry.

[0047] Although embodiments of the present application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made therein without departing from the principles and spirit of the application, the scope of which is defined by the appended claims and their equivalents.

[0048] The above describes the present application and its embodiments, which is not restrictive, but only one of the embodiments of the present application, and the actual application is not limited thereto. In summary, if a person skilled in the art is inspired by it, without departing from the purpose of the present application, without creative design, similar ways and embodiments of the technical solution should belong to the protection scope of the present application.

Claims

1. An ultrathin, high-light-shielding polyimide composite film, characterized in that, It includes a transparent polyimide substrate layer, a light-shielding layer, and an anti-reflective layer; the light-shielding layer is disposed between the transparent polyimide substrate layer and the anti-reflective layer; the light-shielding layer comprises a nano-carbon material composite system and a fluorinated resin.

2. The ultrathin, high-light-shielding polyimide composite film according to claim 1, characterized in that, The thickness of the transparent polyimide substrate layer is 4-6 μm, and its transmittance at a wavelength of 550 nm is greater than 90%.

3. The ultra-thin, high-light-shielding polyimide composite film according to claim 1, characterized in that, The thickness of the light-shielding layer is 2-4 μm, and its transmittance at a wavelength of 550 nm is less than 0.05%.

4. The ultrathin, high-light-shielding polyimide composite film according to claim 1, characterized in that, The thickness of the anti-reflective layer is 0.4-0.6 μm.

5. The ultrathin, high-light-shielding polyimide composite film according to claim 1, characterized in that, The nano-carbon material composite system is composed of nano-graphene and carbon black; based on 100 parts of the total solid mass of the light-shielding layer, the amount of nano-graphene added is 8-12 parts, and the amount of carbon black added is 5 parts.

6. The ultrathin, high-light-shielding polyimide composite film according to claim 5, characterized in that, The nanographene has a sheet diameter of 1-5 μm and 5-10 layers.

7. The ultrathin, high-light-shielding polyimide composite film according to claim 1, characterized in that, Based on 100 parts of the total solid mass of the light-shielding layer, the amount of fluorinated resin added is 15 parts; the fluorinated resin is one or more of soluble polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, and polyvinylidene fluoride.

8. The ultrathin, high-light-shielding polyimide composite film according to claim 1, characterized in that, The light-shielding layer also includes a polyimide precursor resin; the polyimide precursor resin is a polyamic acid solution with a solid content of 15-25% and a viscosity range of 3000-5000 cP.

9. The ultrathin, high-light-shielding polyimide composite film according to claim 1, characterized in that, The anti-reflective layer is formed by vacuum evaporation of one or two of magnesium fluoride and silicon dioxide.

10. A low-temperature pressing process for the ultrathin, high-light-shielding polyimide composite film according to any one of claims 1-9, characterized in that, The method relating to the application of the aforementioned ultra-thin, high-light-shielding polyimide composite film in a camera module includes: fixing the composite film with its transparent polyimide substrate layer facing the image sensor by low-temperature pressing with an adhesive; the process conditions for the low-temperature pressing are: pressing temperature of 70-90℃, pressing pressure of 0.5-1.5MPa, and pressing time of 10-30 seconds; the adhesive is a UV-curable or thermosetting acrylate adhesive with a thickness of 10-30μm.

Images