Preparation method of base film for fingerprint identification chip compression molding packaging release film

Abstract

The invention provides a preparation method of a base film for a fingerprint identification chip compression molding packaging release film, and relates to the technical field of film preparation, and the preparation method comprises the following steps: carrying out melt extrusion on ETFE resin by adopting segmented temperature control to obtain a melt; carrying out gradient cooling on the melt to form a film; performing two-way stretching on the cooled film body, controlling the stretching rate, monitoring the thickness of the film in real time, and combining with a tension sensor to adjust the stretching ratio in real time; the stretched film is slit and rolled, and the taper tension is adjusted in real time during rolling; and carrying out segmented annealing on the rolled film to obtain the base film for the compression molding packaging release film of the fingerprint identification chip. By optimizing the production process of the film, the prepared film is good in tensile property, uniform in crystallinity distribution and small in release force fluctuation.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of thin films, in particular to a preparation method of a base film for a fingerprint recognition chip compression molding packaging release film. BACKGROUND

[0002] The working principle of the fingerprint recognition chip is to convert the fingerprint information into a digital signal by using sensor technology, and then extract the features by algorithm and encrypt the storage, so as to realize fast and safe biological identification. The performance of the chip depends largely on the accuracy of the sensor and the reliability of the packaging process.

[0003] In the compression molding packaging process of the chip, in order to prevent the adhesion of packaging materials such as epoxy resin on the surface of the mold or the chip, a release film is needed. The release film is composed of a release layer and a base film. The base film, as the base material of the release film, directly affects the formability of the release layer. The release film commonly used for compression packaging of fingerprint recognition chips includes PET release film, PI release film and fluorine-based release film. Among them, fluorine-based release film is favored due to its excellent chemical resistance and no silicon pollution characteristics. Compared with the other two films, its most core advantage is that it can achieve stable and reliable separation effect without additional coating.

[0004] ETFE film is a widely used fluorine-based release film. It not only has good tensile properties, but also has the characteristics of low peeling force. However, during the production process of ETFE film, the release force of the mother roll will change with the production batch, thereby affecting the application of ETFE release film. SUMMARY

[0005] The technical problem to be solved by the present application is to provide a preparation method of a base film for a fingerprint recognition chip compression molding packaging release film, which optimizes the production process of the film, and the prepared film not only has good tensile properties, but also has uniform crystallinity distribution and small release force fluctuation.

[0006] To solve the above technical problems, the technical scheme of the present application is:

[0007] A preparation method of a base film for a fingerprint recognition chip compression molding packaging release film, comprising the following steps:

[0008] (1) The ETFE resin is melted and extruded by adopting segmented temperature control, and a melt material is obtained;

[0009] (2) The melt material is gradient cooled to form a film;

[0010] (3) The film body cooled to form a film is bidirectionally stretched, the stretching rate is controlled, the film thickness is monitored in real time, and the stretching ratio is adjusted in real time combined with a tension sensor;

[0011] (4) the stretched film is slitted and wound, and the taper tension is adjusted in real time during winding;

[0012] (5) the wound film is subjected to sectional annealing to obtain a base film for a fingerprint recognition chip compression molding packaging release film.

[0013] Preferably, in step (1), the sectional temperature control conditions are as follows: the feeding zone: 235-245 DEG C, the melting zone: 265-275 DEG C, and the die zone: 260-270 DEG C.

[0014] Preferably, in step (1), a double-screw extruder is used for melt extrusion, and the screw rotation speed during melt extrusion is 30-100 rpm.

[0015] Preferably, in step (2), the gradient cooling conditions are as follows: first, air cooling at 20-30 DEG C is used to control the crystallinity to be 35%-45%, and then cooling at 22-28 DEG C is performed by using a cooling roller.

[0016] Preferably, in step (3), during the longitudinal stretching, the stretching rate is 5-8 m / min, the stretching ratio is 2.5-3.3, and the stretching temperature is 95-105 DEG C.

[0017] Preferably, in step (3), during the transverse stretching, the stretching rate is 2-7 m / min, the stretching ratio is 2.7-3.5, and the stretching temperature is 115-125 DEG C.

[0018] Preferably, during the stretching, a beta-ray thickness gauge is used to monitor the film thickness in real time, and a tension sensor is used to adjust the stretching ratio in real time.

[0019] Preferably, in step (4), the initial tension during winding is 75-85 N / m, the tension is reduced by 4-7 N / m every 10 cm increase in the winding diameter, and the final tension is 45-55 N / m.

[0020] Preferably, in step (4), the environmental conditions during slitting are as follows: the cleanliness is controlled to be ISOClass 6, the particulate matter is less than or equal to 0.5 mu m, the humidity is 40+ / -5 % RH, and the static value is less than or equal to 10 9 Ω / sq.

[0021] Preferably, in step (5), the sectional annealing conditions are as follows: the first stage: 75-85 DEG C for 0.8-1.2 h; and the second stage: 95-105 DEG C for 0.3-0.7 h.

[0022] Thanks to the above technical solutions, the present application has the following advantages:

[0023] The application provides a preparation method of a base film for a fingerprint recognition chip compression molding packaging release film, which optimizes the production conditions of the base film, and the prepared base film has excellent tensile properties, small release force fluctuation, excellent aging resistance and certain waterproof performance.

[0024] When the base film is prepared, the application adopts segmented temperature control extrusion during double screw melting extrusion, and the temperature of the feeding area is reasonably adjusted respectively to prevent uneven plasticization caused by premature melting of the raw materials, the temperature of the melting area is adjusted to ensure complete melting of the ETFE resin and avoid the influence of unmelted grains on film uniformity, and the temperature of the die area is adjusted to reduce the risk of material degradation and ensure the stability of the melt flowability.

[0025] When the base film is prepared, the application adopts gradient cooling during film cooling, first uses air cooling at a certain temperature to cool the film surface quickly, reduces surface defects, and effectively controls the crystallinity, and then enters a cooling roller at a certain temperature to lock the crystalline structure, terminate the molecular chain movement, and ensure the dimensional stability of the film.

[0026] When the base film is prepared by bidirectional stretching, the application reasonably adjusts the stretching ratio, stretching temperature and stretching rate during longitudinal stretching and transverse stretching respectively to ensure balanced molecular chain orientation of the base film and avoid release force deviation caused by anisotropy. Moreover, during stretching, the application also uses a beta-ray thickness gauge to monitor the film thickness in real time, and adjusts the stretching ratio combined with a tension sensor to ensure film consistency.

[0027] When the application is slitting and winding, the initial taper tension is effectively controlled, and the tension is linearly reduced to a certain final tension according to the increase of the winding diameter to prevent film interlayer compression caused by improper tension control or relaxation, which causes large release force fluctuation and even film surface scratches.

[0028] In order to avoid the influence of internal stress release on the stability of the release force of the prepared film during storage, the application anneals the wound base film, and adopts a segmented annealing process, first performs a first annealing treatment at a lower temperature to eliminate extrusion and stretching stress, and then performs a second annealing treatment by increasing the temperature to promote the stabilization of the crystalline structure, thereby ensuring the stable release force of the film. DETAILED DESCRIPTION

[0029] In order to make the above-mentioned objects, features and advantages of the application more clearly understood, the scheme of the application will be further described below. It should be noted that the embodiments of the application and the features in the embodiments can be combined with each other without conflict.

[0030] Many specific details are set forth in the following description in order to provide a thorough understanding of the application. However, the application can be practiced according to other embodiments that can not be described in detail herein; and, obviously, modifications and adaptations of the embodiments described herein are intended to be within the scope of the present application, and can be made by those skilled in the art in light of the detailed description.

[0031] To solve the technical problems in the background art, the present application provides the following technical solutions:

[0032] A preparation method of a base film for a fingerprint recognition chip compression molding packaging release film, comprising the following steps:

[0033] (1) Using segmented temperature control, melt extruding the ETFE resin to obtain a melt;

[0034] (2) Gradient cooling the melt to form a film;

[0035] (3) Bidirectional stretching the film body cooled to form a film, controlling the stretching rate, and real-time monitoring the film thickness and adjusting the stretching ratio in real time combined with a tension sensor;

[0036] (4) Slitting and winding the stretched film, and adjusting the taper tension in real time during winding;

[0037] (5) Segment annealing the wound film to obtain a base film for a fingerprint recognition chip compression molding packaging release film.

[0038] Regarding step (1):

[0039] When preparing the ETFE melt by using a double-screw extruder, the present application uses a segmented temperature control method, effectively controls the melt flowability and crystallization behavior through segmented temperature control, thereby ensuring the micro-uniformity of the film, reducing the release force fluctuation of the film, and ensuring the good stretching performance of the film.

[0040] When segmented temperature control is used, the feeding area needs low-temperature conditions to prevent the resin from softening and caking too early; the temperature of the melting area needs to be higher than the melting point of ETFE to ensure that the resin is fully melted; if the temperature is insufficient, the molecular chains are not completely disentangled, which can cause uneven extrusion of the melt, increase the difference in crystallinity during subsequent film formation, and reduce the release force stability; the temperature of the die area needs to be slightly lower than that of the melting area to reduce the molecular chain breakage caused by high-temperature retention and prevent the resin from thermal degradation and the release force from increasing.

[0041] In some embodiments of the present application, in step (1), the temperature control conditions are as follows: the feeding zone: 235-245℃, the melting zone: 265-275℃, and the die zone: 260-270℃. Specifically, the temperature of the feeding zone can be selected from 235℃, 236℃, 237℃, 238℃, 239℃, 240℃, 241℃, 242℃, 243℃, 244℃, and 245℃, but is not limited thereto. The temperature of the melting zone can be selected from 265℃, 266℃, 267℃, 268℃, 269℃, 270℃, 271℃, 272℃, 273℃, 274℃, and 275℃, but is not limited thereto. The temperature of the die zone can be selected from 260℃, 261℃, 262℃, 263℃, 264℃, 265℃, 266℃, 267℃, 268℃, 269℃, and 270℃, but is not limited thereto. By controlling the temperature in sections, the present application ensures good fluidity of the melt, so that the film forming consistency is good, and the prepared film has not only small fluctuation in release force, but also stable tensile properties.

[0042] While controlling the temperature in sections, the present application also effectively adjusts the screw rotation speed during extrusion, so that the resin particles are mixed more uniformly, local overheating is prevented to cause resin degradation, and the resin is fully melted.

[0043] In some embodiments of the present application, in step (1), a double-screw extruder is used for melt extrusion, and the screw rotation speed during melt extrusion is 30-100 rpm. Specifically, the screw rotation speed can be selected from 30 rpm, 40 rpm, 50 rpm, 60 rpm, 70 rpm, 80 rpm, 90 rpm, and 100 rpm, but is not limited thereto.

[0044] Regarding step (2):

[0045] The present application cools the melt obtained by melt extrusion in a gradient cooling manner, controls the crystallization process of ETFE by precisely controlling the cooling conditions, so as to ensure the stability of the release force, the tensile properties, and the waterproofness of the film. Specifically, the present application first performs air cooling under certain conditions, inhibits the rapid growth of crystals, avoids the formation of large-size spherocrystals, effectively controls the crystallinity, and forms a more uniform surface energy distribution, so that the release film prepared from the base film has a small fluctuation range of release force. Then, the melt is cooled by a cooling roller at a certain temperature, which avoids the uneven shrinkage of the film body caused by single rapid cooling, and avoids the occurrence of internal stress stripe phenomenon.

[0046] In some embodiments of the present application, in step (2), the conditions for gradient cooling are: first using 20-30℃ air cooling, and the air cooling time is controlled to be 5-25s, and then entering the cooling roller cooling at 22-28℃. The specific air cooling temperature can be selected from 20℃, 21℃, 22℃, 23℃, 24℃, 25℃, 26℃, 27℃, 28℃, 29℃, 30℃, but is not limited to this. The temperature of the cooling roller can be selected from 22℃, 23℃, 24℃, 25℃, 26℃, 27℃, 28℃, but is not limited to this.

[0047] The present application arranges the molecular chain in order through gradient cooling, reduces the residual stress of the film body, avoids the partial peeling abnormality of the release layer due to the stress release of the base film during the preparation of the release film. Moreover, the present application forms small crystal nuclei through gradient cooling, air cooling stage cooling, which can be used as stress dispersion points during stretching, and the cooling of the cooling roller can further solidify the amorphous region and improve the cold drawing stress, thereby improving the stretching performance of the film. In addition, the present application effectively controls the crystallinity of the material, makes the surface of the base film smoother, and uniformly arranges the fluorine atoms, so that the prepared base film has good waterproof performance.

[0048] Regarding step (3):

[0049] The present application can effectively regulate the molecular chain arrangement and crystallization behavior of ETFE by optimizing the process conditions of bidirectional stretching, thereby improving the stretching performance and stability of the film. Specifically, during longitudinal stretching, the stretching temperature is lower than the glass transition temperature of ETFE, at this time the activity of the molecular chain of ETFE is moderate, and directional arrangement can be realized; the stretching rate adopts medium-high speed stretching, which makes the molecular chain quickly orient, reduces the relaxation time, inhibits the random coil structure, and reduces the occurrence of large release force fluctuation phenomenon caused by the poor adhesion difference of the release layer after coating; the appropriate stretching ratio makes the molecular chain highly oriented along the longitudinal direction, and improves the longitudinal tensile strength.

[0050] During transverse stretching, the stretching temperature is close to the glass transition temperature of ETFE, which promotes the stretching of the transverse molecular chain; the stretching ratio is optimized at a suitable stretching temperature, which induces the formation of nanoscale grains and reduces surface defects, thereby reducing the release force fluctuation of the film; the appropriately reduced stretching rate is matched with the high stretching temperature, which promotes the slip of the amorphous region molecular chain and ensures the sufficient rearrangement of the molecular chain. Moreover, the present application links the beta-ray thickness gauge and the tension sensor during the stretching process, dynamically adjusts the stretching ratio, can compensate for the thickness deviation caused by temperature fluctuation or uneven raw materials, and reduces the stress concentration point.

[0051] In some embodiments of the present application, in step (3), when longitudinally stretched, the stretching rate is 5-8 m / min, the stretching ratio is 2.5-3.3, and the stretching temperature is 95-105℃. Specifically, the stretching rate can be selected as 5 m / min, 6 m / min, 7 m / min, 8 m / min, 9 m / min, but is not limited thereto. The stretching ratio can be selected as 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, but is not limited thereto. The stretching temperature can be selected as 95℃, 96℃, 97℃, 98℃, 99℃, 100℃, 101℃, 102℃, 103℃, 104℃, 105℃, but is not limited thereto.

[0052] In some embodiments of the present application, in step (3), when transversely stretched, the stretching rate is 2-7 m / min, the stretching ratio is 2.7-3.5, and the stretching temperature is 115-125℃. Specifically, the stretching rate can be selected as 2 m / min, 3 m / min, 4 m / min, 5 m / min, 6 m / min, 7 m / min, but is not limited thereto. The stretching ratio can be selected as 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, but is not limited thereto. The stretching temperature can be selected as 115℃, 116℃, 117℃, 118℃, 119℃, 120℃, 121℃, 122℃, 123℃, 124℃, 125℃, but is not limited thereto.

[0053] In some embodiments of the present application, a beta-ray thickness gauge is used to monitor the film thickness in real time during the stretching process, and a tension sensor is used to adjust the stretching ratio in real time.

[0054] Regarding step (4):

[0055] In the present application, the slitting and winding environment is strictly controlled to ensure the quality of the film, the initial tension during winding is effectively controlled, the taper tension is linearly reduced, the stable release force and the stretching performance of the film are ensured. The appropriate initial tension during winding can reduce air entrainment, the taper tension is linearly reduced as the roll diameter increases, the inner film is prevented from being wrinkled due to excessive pressure of the outer layer, and the fluctuation of the release force of the film is reduced. Moreover, the appropriate taper tension can ensure the mechanical consistency of the film. Moreover, the appropriate taper tension and the slitting and winding environment can ensure that the film has high surface flatness and certain waterproofness.

[0056] In some embodiments of the present application, in step (4), the initial tension during winding is 75-85 N / m, the tension decreases by 4-7 N / m for each 10 cm increase in roll diameter, and finally reaches 45-55 N / m. Specifically, the initial tension can be selected from 75 N / m, 76 N / m, 77 N / m, 78 N / m, 79 N / m, 80 N / m, 81 N / m, 82 N / m, 83 N / m, 84 N / m, 85 N / m, but is not limited thereto. For each 10 cm increase in roll diameter, the tension decrease value can be selected from 4 N / m, 4.5 N / m, 5 N / m, 5.5 N / m, 6 N / m, 6.5 N / m, 7 N / m, but is not limited thereto. The final tension can be selected from 45 N / m, 46 N / m, 47 N / m, 48 N / m, 49 N / m, 50 N / m, 51 N / m, 52 N / m, 53 N / m, 54 N / m, 55 N / m, but is not limited thereto.

[0057] In some embodiments of the present application, in step (4), the environmental conditions during slitting are: control cleanliness: ISO Class 6, particulate matter ≤0.5 μm; humidity: 40 ± 5% RH, static value ≤10 9 Ω / sq.

[0058] Regarding step (5):

[0059] The release force stability and good chemical uniformity and micro-flatness on the film surface, the present application adjusts the crystalline morphology by sectional annealing to release internal stress. Specifically, first eliminate the residual stress of extrusion and stretching at a certain temperature, then perform secondary annealing at high temperature to promote the rearrangement of amorphous molecular chains, fill crystal defects, improve surface density, and promote the stabilization of crystalline structure, thereby reducing the centrifugal force fluctuation of the film, and improving the tensile properties and waterproof performance of the film.

[0060] In some embodiments of the present application, in step (5), the conditions for sectional annealing are: first stage: 75-85℃ for 0.8-1.2 h; second stage: 95-105℃ for 0.3-0.7 h. Specifically, the temperature for first stage annealing treatment can be selected from 75℃, 76℃, 77℃, 78℃, 79℃, 80℃, 81℃, 82℃, 83℃, 84℃, 85℃, but is not limited thereto. The time for first stage annealing treatment can be selected from 0.8 h, 0.9 h, 1.0 h, 1.1 h, 1.2 h, but is not limited thereto. The temperature for second stage treatment can be selected from 95℃, 96℃, 97℃, 98℃, 99℃, 100℃, 101℃, 102℃, 103℃, 104℃, 105℃, but is not limited thereto. The time for second stage annealing treatment can be selected from 0.3 h, 0.4 h, 0.5 h, 0.6 h, 0.7 h, but is not limited thereto.

[0061] For a further understanding of the present application, preferred embodiments thereof will be described in conjunction with examples, it being understood, however, that this description is made only by way of further illustration and not as a limitation on the right claims.

[0062] Example 1

[0063] A preparation method of a base film for a fingerprint recognition chip compression molding packaging release film, comprising the following steps:

[0064] (1) The ETFE resin is added to the twin-screw extruder for melt extrusion to obtain a melt material; the screw rotation speed is 30 rpm during melt extrusion, and the temperature is controlled in sections, specifically: feeding zone: 235°C, melting zone: 265°C, die zone: 260°C;

[0065] (2) The melt material is first cooled by air at 20°C for 10s, and then enters the cooling roller with a rotation speed of 11 rpm and a temperature of 22°C;

[0066] (3) The film body cooled by the cooling roller is first stretched longitudinally under the conditions of a stretching temperature of 95°C, a stretching rate of 5m / min, and a stretching ratio of 2.5, and then stretched transversely under the conditions of a stretching temperature of 115°C, a stretching rate of 2m / min, and a stretching ratio of 2.7; the film thickness is monitored in real time by a beta-ray thickness gauge during the longitudinal and transverse stretching processes, and the stretching ratio is adjusted in real time by a tension sensor;

[0067] (4) The stretched film is cut and wound; the environmental conditions during cutting are: control cleanliness: ISO Class 6, particulate matter ≤0.5μm; humidity: 40±5%RH, static value ≤10 9 Ω / sq; the taper tension is adjusted in real time during winding, specifically, a polyurethane winding core with a Shore A hardness of 75 is used during winding, the initial tension during winding is 75N / m, the tension is reduced by 4N / m every 10cm increase in winding diameter, and finally reaches 45N / m;

[0068] (5) The wound film is treated at 75°C for 0.8h, and then treated at 95°C for 0.3h; the annealed film is packaged to obtain a base film for a fingerprint recognition chip compression molding packaging release film.

[0069] Example 2

[0070] A preparation method of a base film for a fingerprint recognition chip compression molding packaging release film, comprising the following steps:

[0071] (1) adding ETFE resin into a twin-screw extruder for melt extrusion to obtain a melt; the screw rotation speed is 50 rpm during melt extrusion, and segmented temperature control is adopted, specifically: feeding zone: 240°C, melting zone: 268°C, die zone: 265°C;

[0072] (2) the above melt is first cooled by air at 25°C for 15s, and then enters a cooling roller with a rotation speed of 12 rpm and a temperature of 25°C;

[0073] (3) the film body cooled by the cooling roller is first stretched longitudinally under the conditions of a stretching temperature of 100°C, a stretching speed of 6 m / min, and a stretching ratio of 3.0, and then stretched transversely under the conditions of a stretching temperature of 120°C, a stretching speed of 5 m / min, and a stretching ratio of 3.3, wherein a beta-ray thickness gauge is used to monitor the film thickness in real time during the longitudinal and transverse stretching, and a tension sensor is used to adjust the stretching ratio in real time;

[0074] (4) the stretched film is cut and wound; the environmental conditions during cutting are: control cleanliness: ISO Class 6, particulate matter ≤0.5 μm; humidity: 40±5% RH, static value ≤10 9 Ω / sq; the taper tension is adjusted in real time during winding, specifically, a polyurethane winding core with a Shore A hardness of 75 is used during winding, the initial tension during winding is 80 N / m, the tension is reduced by 5 N / m every 10 cm increase in winding diameter, and finally the tension is 50 N / m;

[0075] (5) the wound film is treated at 80°C for 1.0 h, and then treated at 100°C for 0.5 h; the annealed film is packaged to obtain a base film for a fingerprint recognition chip compression molding packaging release film.

[0076] Example 3

[0077] A preparation method of a base film for a fingerprint recognition chip compression molding packaging release film, comprising the following steps:

[0078] (1) adding ETFE resin into a twin-screw extruder for melt extrusion to obtain a melt; the screw rotation speed is 100 rpm during melt extrusion, and segmented temperature control is adopted, specifically: feeding zone: 245°C, melting zone: 275°C, die zone: 270°C;

[0079] (2) the above melt is first cooled by air at 30°C for 25s, and then enters a cooling roller with a rotation speed of 13 rpm and a temperature of 28°C;

[0080] (3) The film body after cooling by the cooling roller is first subjected to longitudinal stretching under the conditions of a stretching temperature of 105°C, a stretching rate of 8 m / min, and a stretching ratio of 3.3, and then subjected to transverse stretching under the conditions of a stretching temperature of 125°C, a stretching rate of 7 m / min, and a stretching ratio of 3.5, and a beta ray thickness gauge is used to monitor the film thickness in real time during the longitudinal and transverse stretching, and a tension sensor is used to adjust the stretching ratio in real time;

[0081] (4) The stretched film is slitted and wound; the environmental conditions during slitting are: control cleanliness: ISO Class 6, particulate matter ≤0.5 μm; humidity: 40±5% RH, static value ≤10 9 Ω / sq; during winding, the taper tension is adjusted in real time, specifically, a polyurethane winding core with a Shore A hardness of 75 is used during winding, the initial tension during winding is 85 N / m, the tension is reduced by 7 N / m every 10 cm increase in winding diameter, and finally the tension is 55 N / m;

[0082] (5) The wound film is treated at 85°C for 1.2 h, and then treated at 105°C for 0.7 h; the annealed film is packaged to obtain a base film for a fingerprint recognition chip compression molding packaging release film.

[0083] Comparative Example 1

[0084] The difference between this comparative example and Example 3 is that in step (1), during melt extrusion, no staged temperature control is performed, and the extrusion temperature is controlled at 275°C, and the other operations are the same as in Example 3.

[0085] Comparative Example 2

[0086] The difference between this comparative example and Example 3 is that in step (2), during cooling, only the process of cooling the melt at 30°C for 25 s to control the crystallinity to 45% is included, and the other operations are the same as in Example 3.

[0087] Comparative Example 3

[0088] The difference between this comparative example and Example 3 is that in step (3), the stretching ratio during longitudinal stretching is 3.5, and the other operations are the same as in Example 3.

[0089] Comparative Example 4

[0090] The difference between this comparative example and Example 3 is that in step (3), the stretching ratio during transverse stretching is 4.0, and the other operations are the same as in Example 3.

[0091] Comparative Example 5

[0092] The difference between this comparative example and Example 3 is that in step (4), the taper tension during winding is controlled at 85 N / m, without linear control, and the other operations are the same as in Example 3.

[0093] Comparative Example 6

[0094] The difference between this comparative example and Example 3 is that in step (4), the taper tension control during winding is 55 N / m, without linear control, and other operations are the same as in Example 3.

[0095] Comparative Example 7

[0096] The difference between this comparative example and Example 3 is that in step (4), the taper tension control during winding is linearly adjusted, with the diameter of each roll increasing by 10 cm and the tension decreasing by 10 N / m, until finally reaching 55 N / m, and other operations are the same as in Example 3.

[0097] Comparative Example 8

[0098] The difference between this comparative example and Example 3 is that in step (4), the taper tension control during winding is linearly adjusted, with the diameter of each roll increasing by 10 cm and the tension decreasing by 2 N / m, until finally reaching 55 N / m, and other operations are the same as in Example 3.

[0099] Comparative Example 9

[0100] The difference between this comparative example and Example 3 is that in step (5), the wound film is treated at 85°C, and the total annealing treatment time and other operations are the same as in Example 3.

[0101] Comparative Example 10

[0102] The difference between this comparative example and Example 3 is that in step (5), the wound film is treated at 105°C, and the total annealing treatment time and other operations are the same as in Example 3.

[0103] Comparative Example 11

[0104] The difference between this comparative example and Example 3 is that the stretched film is annealed before being slit and wound, and other operations are the same as in Example 3.

[0105] Test 1:

[0106] 1. The tensile properties of the base film of the release film prepared in the above examples and comparative examples were tested.

[0107] 2. The water drop angle of the film prepared in the above examples and comparative examples was tested using a water drop angle tester.

[0108] 3. The release force was tested by standard peeling method. Specifically, TESA 7475 tape was attached to the base film of the release film of the above examples and comparative examples, respectively. After 24 h, the peeling force was measured by a tensile strength machine at an angle of 180° and a speed of 300 mm / min. The average value of multiple samples was taken as the final release force. The centrifugal force fluctuation of the base film in the same batch was calculated according to the release force of multiple samples.

[0109] The test results are shown in Table 1.

[0110] Table 1

[0111]

[0112] As can be seen from the test results in Table 1, the film prepared by optimizing the draw ratio, winding tension, annealing and other conditions in the film production process has excellent comprehensive performance.

[0113] In Comparative Example 1, no segmented temperature control was performed during melt extrusion, and the film was directly extruded at a high temperature of 275℃. The transverse tensile strength and longitudinal tensile strength of the prepared film decreased sharply. This is because high temperature leads to local degradation of the resin and breakage of the molecular chain, and the melt uniformity decreases and the number of crystallization defects increases. High temperature causes the formation of a more dense crystalline layer on the surface of the film, resulting in a slight increase in the water drop angle of the film. In addition, poor melt uniformity leads to uneven film thickness and inconsistent release layer distribution. After aging, the adhesive tape penetrates into the defect area, and the peeling force fluctuates.

[0114] In Comparative Example 2, only air cooling was used during the cooling of the melt after melt extrusion, resulting in insufficient cooling rate, high and uneven crystallinity of the material, increased film brittleness, and significant reduction in longitudinal tensile strength and transverse tensile strength. Moreover, low cooling rate can form large-size spherulites, increase the surface roughness of the film, and abnormally increase the hydrophobicity. The inconsistent release force is caused by the fluctuation of the adhesive tape contact area.

[0115] In Comparative Example 3, the longitudinal draw ratio is too high, resulting in excessive orientation of the molecular chain in the longitudinal direction and sparse arrangement of the molecular chain in the transverse direction, leading to unbalanced mechanical properties. In Comparative Example 4, the transverse draw ratio is too high, making the film thin, increasing the risk of molecular chain breakage, and excessive transverse stretching can damage the longitudinal orientation structure, resulting in a slight decrease in the transverse tensile strength and longitudinal tensile strength of the film. Moreover, excessive stretching causes uneven film thickness, and the difference in release force between different areas of the same film increases.

[0116] In Comparative Example 5, the taper tension control was cancelled when winding the film, and a high tension of 85 N / m was used throughout, which resulted in a significant decrease in the transverse tensile strength of the film. This is because the high tension limits the transverse shrinkage of the film, and the internal stress accumulates, and the molecular chains cannot relax. Moreover, the high tension causes the inner layer of the film roll to be compressed and deformed, resulting in a "hard core" effect. The inner release layer is extruded and densified, and the outer layer is loose, and the release force of the film is unevenly distributed. In Comparative Example 6, the taper tension control was cancelled when winding the film, and a low tension of 55 N / m was used throughout, which resulted in a sudden drop in the transverse tensile strength of the film due to insufficient tension, which caused the film layers to not fit tightly, the molecular chains to relax excessively, and the structure to be loose. In addition, the insufficient tension caused the film layers to slide, the winding was tight and loose, the shrinkage of different areas of the film roll was different, and the release force fluctuation increased. In Comparative Example 7, the taper tension decreased too much when winding the film, and the sudden drop in tension caused a sudden change in stress between the inner and outer layers of the film roll, and the local area relaxed unevenly, which caused a certain decrease in the transverse tensile strength of the film. Moreover, the sudden drop in tension caused the outer layer of the film roll to be too loose and the inner layer to be too tight, and the release force fluctuation of the film of the same batch increased slightly. In Comparative Example 8, the taper tension decreased too little when winding the film, and the outer layer tension was too high, which caused the molecular chains to be too tightly stretched longitudinally, the transverse chain segments to be squeezed by the longitudinal direction, and the stress to accumulate, which caused a certain decrease in the transverse tensile strength and the longitudinal tensile strength of the film. Moreover, the high tension of the outer layer caused the film layers to fit too tightly, and the adhesive tape was unevenly stressed when peeled off, which caused the release force to fluctuate.

[0117] In Comparative Example 9, only low-temperature annealing was used for the wound film, and the insufficient annealing was not enough to eliminate the residual stress in the high-orientation area, which caused a significant decrease in the transverse tensile strength of the film, uneven stress release, and partial warping of the release layer. Moreover, low-temperature annealing caused insufficient crystallization and increased surface hydrophobicity. In Comparative Example 10, only high-temperature annealing was used for the wound film, which caused the molecular chains to relax excessively, and the orientation structure to be destroyed, which caused a significant decrease in the transverse tensile strength of the film. Moreover, direct high-temperature annealing caused the molecular chains to relax excessively, the bonding force between the release layer and the base film to weaken, and the release force stability of the film to decrease. In Comparative Example 11, the stretched film was directly annealed and then slit and wound, which introduced new mechanical stress that could not be eliminated by subsequent processes, which caused a decrease in the transverse tensile strength of the film, micro-cracks at the edges of the film roll, and an increase in the dispersion of the release force of the film.

[0118] The principles and implementations of the present application are described herein with specific examples, and the above descriptions of the examples are only used to help understand the method of the present application and its core ideas, including the best mode, and also enable any person skilled in the art to practice the present application, including manufacturing and using any device or system, and implementing any combined method. It should be noted that, for those skilled in the art, some improvements and modifications can be made to the present application without departing from the principles of the present application, and these improvements and modifications also fall within the protection scope of the claims of the present application. The scope of patent protection of the present application is defined by the claims, and can include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements similar to the literal expressions of the claims, or if they include equivalent structural elements that are not substantially different from the literal expressions of the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. A method for preparing a base film for a release film used in the compression molding and packaging of fingerprint recognition chips, characterized in that, Includes the following steps: (1) Using segmented temperature control, ETFE resin is melt-extruded to obtain melt; (2) The above melt is subjected to gradient cooling to form a film; (3) The film body cooled into a film is subjected to biaxial stretching, the stretching rate is controlled, the film thickness is monitored in real time, and the stretching ratio is adjusted in real time in conjunction with the tension sensor. (4) Cut and wind up the stretched film, and adjust the taper tension in real time during winding; (5) The wound film is annealed in sections to obtain a base film for the release film of the fingerprint recognition chip compression molding and packaging.

2. The method for preparing a base film for a release film used in the compression molding and packaging of a fingerprint recognition chip according to claim 1, characterized in that, In step (1), the temperature control conditions for each segment are: feeding zone: 235-245℃, melting zone: 265-275℃, and die head zone: 260-270℃.

3. The method for preparing a base film for a release film used in the compression molding and packaging of a fingerprint recognition chip according to claim 1, characterized in that, In step (1), a twin-screw extruder is used for melt extrusion, and the screw speed during extrusion is 30-100 rpm.

4. The method for preparing a base film for a release film used in the compression molding and packaging of a fingerprint recognition chip according to claim 1, characterized in that, In step (2), the gradient cooling conditions are as follows: first, air cooling at 20-30℃ is used to control the crystallinity to 35%-45%, and then cooling is performed by cooling rollers at 22-28℃.

5. The method for preparing a base film for a release film used in the compression molding and packaging of a fingerprint recognition chip according to claim 1, characterized in that, In step (3), during longitudinal stretching, the stretching rate is 5-8 m / min, the stretching ratio is 2.5-3.3, and the stretching temperature is 95-105℃.

6. The method for preparing a base film for a release film used in the compression molding and packaging of a fingerprint recognition chip according to claim 1, characterized in that, In step (3), during transverse stretching, the stretching rate is 2-7 m / min, the stretching ratio is 2.7-3.5, and the stretching temperature is 115-125℃.

7. The method for preparing a base film for a release film used in the compression molding and packaging of a fingerprint recognition chip according to claim 1, characterized in that, During the stretching process, a beta-ray thickness gauge is used to monitor the film thickness in real time, and the stretching ratio is adjusted in real time in conjunction with a tension sensor.

8. The method for preparing a base film for a release film used in the compression molding and packaging of a fingerprint recognition chip according to claim 1, characterized in that, In step (4), the initial tension during winding is 75-85 N / m. During winding, the tension decreases by 4-7 N / m as the diameter of each roll increases by 10 cm, eventually reaching 45-55 N / m.

9. The method for preparing a base film for a release film used in the compression molding and packaging of a fingerprint recognition chip according to claim 1, characterized in that, In step (4), the environmental conditions during slitting are: cleanliness control: ISO Class 6, particulate matter ≤0.5μm; Humidity: 40±5%RH, Static electricity value ≤10 9 Ω / sq.

10. The method for preparing a base film for a release film used in the compression molding and packaging of a fingerprint recognition chip according to claim 1, characterized in that, In step (5), the conditions for segmented annealing are: first stage: treatment at 75-85℃ for 0.8-1.2h; second stage: treatment at 95-105℃ for 0.3-0.7h.

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