A double-sided printed ultra-low transmission polyester-based film and a preparation method thereof

Abstract

The present application relates to the polyester-based film manufacturing field, especially to a double-sided printing ultra-low light transmission polyester-based film and a preparation method thereof, the film is composed of three layers of composite, the middle layer is a gray light-absorbing support layer, and the gray light-absorbing support layer has the same thickness on both sides of the super-white surface layer. The present application forms a multilayer light blocking system through different structural configurations, reduces the light transmission effect, ensures the use strength of the film, and improves the stability of the film.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of polyester-based film manufacturing, in particular to a double-sided printed ultra-low light transmission polyester-based film and a preparation method thereof. BACKGROUND

[0002] The polyester-based film is used for double-sided printed patterns, and its application scenario is mainly to make hanging printed posters. The poster needs to have low light transmission, and the patterns on the two sides will not affect each other after hanging, and the visual effect is good. There are many studies on polyester-based films in the prior art, such as CN117021725A, a crystalline easy-to-recycle polyester heat-shrinkable film and a preparation method thereof, the film layer structure is A / B / A three-layer structure; the raw material of A layer is composed of PETG, functional masterbatch and PET; the raw material of B layer is composed of modified PET, PET, nucleating agent, chain extender and foaming agent, additives are introduced to improve the crystallinity and melting point of the film, and the prepared polyester heat-shrinkable film has good recycling characteristics, crystallizability, printability, shrinkability and low shrinkage force characteristics. For example, CN202310824959.6, an online coated polyester film for high-adhesion UV inkjet printing, solves the problem of low adhesion between polyester film and UV inkjet printing material, and has the characteristics of low cost, high efficiency, non-toxicity and strong adhesion. It can be seen that the research on polyester-based film in the prior art mainly focuses on adhesion and shrinkage, and there is a lack of research on low light transmission and strong adaptability. SUMMARY

[0003] The present application provides a double-sided printed ultra-low light transmission polyester-based film and a preparation method thereof to reduce the light transmission of the film and improve the durability of the film, which overcomes the shortcomings of the prior art. The specific technical solutions are as follows:

[0004] A double-sided printed ultra-low light transmission polyester-based film, which is composed of three layers of composite, and the middle layer is a gray light-absorbing support layer, and the gray light-absorbing support layer is flanked by two ultra-white surface layers with the same thickness;

[0005] The ultra-white surface layer is prepared from the following raw materials in parts by mass:

[0006] 75-78 parts of PET resin, 1-2 parts of light-absorbing filler, 5-7 parts of ultra-fine calcium carbonate, 0.3-0.5 parts of stearic acid amide, 0.1-0.2 parts of oleic acid amide, and 0.8-0.9 parts of zinc oxide; the particle size of the ultra-fine calcium carbonate is 80-100 nm;

[0007] The gray light-absorbing support layer is prepared from the following raw materials:

[0008] 88-91 parts of PET resin, 0.1-0.15 parts of solvent black 3, 2-4 parts of light-absorbing filler, 1-1.5 parts of silicon dioxide, and 0.08-0.09 parts of antioxidant 1076;

[0009] Further, the light-absorbing filler is prepared from 8-13 parts of structural ceramic material, 11-13 parts of carbon nanotube, and 0.6-0.8 parts of rare earth oxide.

[0010] Further, the structural ceramic material is composed of 1-3 parts of silicon nitride, 1-2 parts of zirconium oxide, 1-1.6 parts of titanium oxide, 1-2 parts of magnesium silicon nitride, and 4-9 parts of aluminum oxide.

[0011] Further, the rare earth oxide is composed of 0.3-0.7 parts of yttrium trioxide, 0.1-0.3 parts of lanthanum oxide, and 0.2-0.28 parts of cerium oxide.

[0012] Further, the gray light-absorbing support layer accounts for 60-63% of the total thickness.

[0013] The preparation method of the double-sided printing ultra-low light transmission polyester-based film is as follows:

[0014] (3) Preparation of light-absorbing filler

[0015] A raw material preparation

[0016] 1-3 parts of silicon nitride, 1-2 parts of zirconium oxide, 1-1.6 parts of titanium oxide, 1-2 parts of magnesium silicon nitride, 4-9 parts of aluminum oxide, 0.3-0.7 parts of yttrium trioxide, 0.1-0.3 parts of lanthanum oxide, 0.2-0.28 parts of cerium oxide, and 11-13 parts of carbon nanotube are prepared by mass fraction;

[0017] B Mixing of raw materials

[0018] The lanthanum oxide and cerium oxide are mixed, and 20-25 times the mass of pure water is added. Hydrochloric acid solution is added dropwise in the pure water to dissolve the lanthanum oxide and cerium oxide. Silicon nitride and carbon nanotube are added to the dissolved solution, and stirring is carried out at a rate of 70-80 r / min. Sodium hydroxide solution is gradually added dropwise until no precipitate is generated in the solution to stop adding sodium hydroxide.

[0019] The solution is filtered, and the precipitate is washed with pure water for 3-5 times and dried for standby use.

[0020] C Ball milling

[0021] The mixture obtained in the above step is mixed with zirconium oxide, titanium oxide, magnesium silicon nitride, aluminum oxide, and yttrium trioxide, and 1-2 times the mass of ethanol solution of all materials is added into the ball mill for 13-18 h. The adhesive is added in the ball mill, and ball milling is carried out for 5-8 h.

[0022] D Sintering

[0023] The slurry obtained in the previous step is granulated in a spray drying device, dried at 100-150 DEG C for 2-4h under argon protection, calcination temperature is 2100 DEG C-2300 DEG C, and calcination time is 6-7h to obtain the light-absorbing filler;

[0024] (4) preparation of super-white surface layer

[0025] 75-78 parts of PET resin, 1-2 parts of light-absorbing filler, 5-7 parts of superfine calcium carbonate, 0.3-0.5 parts of stearic acid amide, 0.1-0.2 parts of oleic acid amide, and 0.8-0.9 parts of zinc oxide are mixed and melted, and then the material is extruded and mixed uniformly for multiple times, poured into a mold and cast into a film to obtain a super-white surface layer.

[0026] (3) preparation of gray light-absorbing support layer

[0027] 88-91 parts of PET resin, 0.1-0.15 parts of solvent black 3, 2-4 parts of light-absorbing filler, 1-1.5 parts of silicon dioxide, and 0.08-0.09 parts of antioxidant 1076 are uniformly mixed, and the slurry is cast on the upper surface of the super-white surface layer in the mold of step (2) to obtain a gray light-absorbing support layer, and the super-white surface layer is formed on the upper surface of the gray light-absorbing support layer by repeating step (2); the composite film is placed on a quenching rod for cooling and bidirectional stretching.

[0028] Further, the mass fraction of the hydrochloric acid solution is 17-20%.

[0029] Further, the sodium hydroxide solution is 35-38%.

[0030] Further, the adhesive is mixed by polyvinyl alcohol and calcium cellulose at a mass ratio of 1:0.1-0.13.

[0031] Further, the volume fraction of ethanol in the ethanol solution is 66-73%.

[0032] Further, the amount of the adhesive is 15-19% of the mass of the ethanol solution.

[0033] The beneficial effects of the present application are:

[0034] The double-sided printing ultra-low light transmission polyester-based film of the present application is composed of three layers of composite, wherein the middle layer is a gray light-absorbing support layer, and the gray light-absorbing support layer is flanked by two ultra-white surface layers of the same thickness, forming a multi-layer light barrier system through different structural configurations to reduce the light transmission effect. The ultra-white surface layer is prepared from polyester, light-absorbing filler, ultra-fine calcium carbonate, stearic acid amide, oleic acid amide, and zinc oxide, containing various light barrier particles to improve the light barrier effect while ensuring the use strength of the film; the gray light-absorbing support layer is prepared from PET resin, solvent black 3, light-absorbing filler, silicon dioxide, and antioxidant 1076 to strengthen the low light transmission of the film. The light-absorbing filler is prepared from silicon nitride, zirconium oxide, titanium oxide, silicon nitride magnesium, aluminum oxide, yttrium trioxide, lanthanum oxide, cerium oxide, and carbon nanotubes, having stronger structural particles that can adsorb other fillers to improve the stability of the film.

[0035] In the preparation of the light-absorbing filler of the present application, lanthanum oxide and cerium oxide are mixed, pure water is added, and a hydrochloric acid solution is then dropped to dissolve the lanthanum oxide and cerium oxide. Silicon nitride and carbon nanotubes are then added to the solution, allowing the silicon nitride and carbon nanotubes to adsorb lanthanum ions and cerium ions in all directions. Finally, a sodium hydroxide solution is gradually dropped, allowing the silicon nitride and carbon nanotubes to be uniformly covered with lanthanum ions and cerium ions to form an alkaline precipitate. The resulting mixture is ball milled with zirconium oxide, titanium oxide, silicon nitride magnesium, aluminum oxide, and yttrium trioxide to achieve higher uniformity of the materials. The mixture is then granulated in a spray drying device under the action of a binder. Under argon protection, the alkaline precipitate of lanthanum ions and cerium ions is decomposed into oxides and uniformly mixed with other components. The released water vapor improves the pore structure of the ceramic particles, allowing the light-absorbing filler in the final film structure to better adsorb ultra-fine calcium carbonate, solvent black, and other materials. After forming a unified whole with the film structure, the light-absorbing filler can also uniformly release rare earth elements to strengthen the film structure, improve the light barrier effect of the film, reduce the light transmission rate, and strengthen the use effect of the film.

[0036] In the present application, the light-absorbing filler is mixed and sintered from structural ceramic materials, carbon nanotubes, and rare earth oxides to form complex surface structure particles with a grain arrangement array, allowing the light to undergo multiple diffraction and reflection when passing through the film structure, thereby improving the blocking effect of the light. The high hardness of silicon nitride in the structural ceramic material improves the stability of the sintered particles, the high refractive index of zirconium oxide increases the bending of light, the titanium oxide increases the light extinction, the silicon nitride magnesium acts as a sintering aid to strengthen the fusion of each structure, and the aluminum oxide reduces the cost to fully fuse and form a stable particle structure. The rare earth oxides are yttrium trioxide, lanthanum oxide, and cerium oxide, which use yttrium oxide to improve the interface fusion degree of the material and enhance the structural stability of the particle forming material, and the low thermal conductivity limits the temperature transmission to reduce the aging of the film layer; the lanthanum oxide refines the grain size and promotes sintering densification; and the cerium oxide enhances the hardness, wear resistance, and impact resistance of the grain, improving the tolerance of the film. DETAILED DESCRIPTION

[0037] Example 1

[0038] A double-sided printing ultra-low light transmission polyester-based film, which is composed of three layers of composite, wherein the middle layer is a gray light-absorbing support layer, and the same thickness of super-white surface layer is on both sides of the gray light-absorbing support layer; the gray light-absorbing support layer accounts for 60-65% of the total thickness;

[0039] The super-white surface layer is prepared from the following raw materials in parts by mass:

[0040] 75 parts of PET resin, 1 part of light-absorbing filler, 6 parts of superfine calcium carbonate, 0.3 parts of stearic acid amide, 0.1 parts of oleic acid amide, 0.8 parts of zinc oxide; the particle size of the superfine calcium carbonate is 80 nm;

[0041] The gray light-absorbing support layer is prepared from the following raw materials:

[0042] Take 88 parts of PET resin, 0.1 parts of solvent black 3, 2 parts of light-absorbing filler, 1 part of silicon dioxide, 0.08 parts of antioxidant 1076;

[0043] The light-absorbing filler is prepared from 1 part of silicon nitride, 1 part of zirconium oxide, 1 part of titanium oxide, 1 part of silicon nitride magnesium, 4 parts of aluminum oxide, 0.3 parts of yttrium trioxide, 0.1 parts of lanthanum oxide, 0.2 parts of cerium oxide, and 11 parts of carbon nanotubes;

[0044] The preparation method of the double-sided printing ultra-low light transmission polyester-based film is as follows:

[0045] (1) Light-absorbing filler preparation

[0046] A raw material preparation

[0047] Take silicon nitride, zirconium oxide, titanium oxide, silicon nitride magnesium, aluminum oxide, yttrium trioxide, lanthanum oxide, cerium oxide, and carbon nanotubes for standby;

[0048] B raw material mixing

[0049] Mix lanthanum oxide and cerium oxide, add 20 times the mass of pure water, and drop hydrochloric acid solution into the pure water to dissolve lanthanum oxide and cerium oxide. Add silicon nitride and carbon nanotubes to the dissolution solution, stir at a speed of 70 r / min, and gradually drop sodium hydroxide solution into the solution until no precipitate is generated in the solution;

[0050] Filter the solution, wash the precipitate with pure water for 3 times, and dry for standby;

[0051] The mass fraction of the hydrochloric acid solution is 17%, and the mass fraction of the sodium hydroxide solution is 35%;

[0052] C ball milling

[0053] The mixture obtained in the previous step is mixed with zirconium oxide, titanium oxide, silicon magnesium nitride, aluminum oxide, yttrium trioxide, and an ethanol solution with a mass of 1 times the total mass of the materials is added into a ball mill and ball milled for 13 h; an adhesive with a mass of 15% of the ethanol solution is added into the ball mill and ball milled for 5 h;

[0054] The adhesive is mixed from polyvinyl alcohol and calcium cellulose at a mass ratio of 1:0.1; the volume fraction of ethanol in the ethanol solution is 66%;

[0055] D sintering

[0056] The slurry obtained in the previous step is granulated in a spray drying device, dried at 100°C for 2 h, calcined at a temperature of 2100°C for 6 h under argon protection, and the light-absorbing filler is obtained;

[0057] (2) Preparation of an ultra-white surface layer

[0058] PET resin, light-absorbing filler, ultra-fine calcium carbonate, stearic acid amide, oleic acid amide, and zinc oxide are mixed and melted, and after the materials are mixed uniformly through multiple extrusions, the mixture is poured into a mold to be cast into a film to obtain an ultra-white surface layer;

[0059] (3) Preparation of a gray light-absorbing support layer

[0060] PET resin, solvent black 3, light-absorbing filler, silicon dioxide, and antioxidant 1076 are uniformly mixed and cast on the surface of the ultra-white surface layer in the mold of step (2) to obtain a gray light-absorbing support layer, and the ultra-white surface layer is formed on the surface of the gray light-absorbing support layer by repeating step (2); the composite film is placed on a quenching rod for cooling and bidirectional stretching.

[0061] Example 2

[0062] A double-sided printing ultra-low light transmission polyester-based film is composed of a three-layer composite, wherein the middle layer is a gray light-absorbing support layer, and the gray light-absorbing support layer is flanked by ultra-white surface layers with the same thickness; the gray light-absorbing support layer accounts for 65% of the total thickness;

[0063] The ultra-white surface layer is prepared from the following raw materials in parts by mass:

[0064] 78 parts of PET resin, 2 parts of light-absorbing filler, 5 parts of ultra-fine calcium carbonate, 0.5 parts of stearic acid amide, 0.2 parts of oleic acid amide, and 0.9 parts of zinc oxide; the particle size of the ultra-fine calcium carbonate is 100 nm;

[0065] The gray light-absorbing support layer is prepared from the following raw materials:

[0066] 91 parts of PET resin, 0.15 parts of solvent black 3, 4 parts of light-absorbing filler, 1.5 parts of silicon dioxide, and 0.09 parts of antioxidant 1076;

[0067] The light-absorbing filler is prepared from 3 parts of silicon nitride, 2 parts of zirconium oxide, 1.6 parts of titanium oxide, 2 parts of magnesium silicon nitride, 9 parts of aluminum oxide, 0.7 parts of yttrium trioxide, 0.3 parts of lanthanum oxide, 0.28 parts of cerium oxide, and 13 parts of carbon nanotubes;

[0068] The preparation method of the double-sided printing ultra-low light transmission polyester-based film comprises the following steps:

[0069] (1) Preparation of light-absorbing filler

[0070] A raw material preparation

[0071] Take silicon nitride, zirconium oxide, titanium oxide, magnesium silicon nitride, aluminum oxide, yttrium trioxide, lanthanum oxide, cerium oxide, and carbon nanotubes for standby;

[0072] B Mixing of raw materials

[0073] Mix lanthanum oxide and cerium oxide, add 25 times the mass of pure water, and drop hydrochloric acid solution into the pure water to dissolve the lanthanum oxide and cerium oxide. Add silicon nitride and carbon nanotubes to the dissolved solution, stir at a speed of 80 r / min, and gradually drop sodium hydroxide solution until no precipitate is generated in the solution to stop dropping sodium hydroxide.

[0074] Filter the solution, wash the precipitate with pure water 5 times, and dry for standby;

[0075] The mass fraction of the hydrochloric acid solution is 20%; the mass fraction of the sodium hydroxide solution is 38%;

[0076] C Ball milling

[0077] Mix the mixture obtained in the previous step with zirconium oxide, titanium oxide, magnesium silicon nitride, aluminum oxide, and yttrium trioxide, add an ethanol solution with a mass of 2 times the total mass of the materials into a ball mill, and ball mill for 18 h. Add an adhesive with a mass of 19% of the mass of the ethanol solution into the ball mill, and ball mill for 8 h.

[0078] The adhesive is mixed by polyvinyl alcohol and calcium cellulose at a mass ratio of 1:0.13; the volume fraction of ethanol in the ethanol solution is 73%;

[0079] D Sintering

[0080] Granulate the slurry obtained in the previous step in a spray drying device, dry at 150℃ for 4 h, and calcine at a temperature of 2300℃ for 7 h under argon protection to obtain the light-absorbing filler.

[0081] (2) Preparation of ultra-white surface layer

[0082] The PET resin, light-absorbing filler, superfine calcium carbonate, stearic acid amide, oleic acid amide and zinc oxide are mixed and melted, and after the materials are mixed uniformly through multiple extrusions, the mixture is poured into a mold to flow cast into a film to obtain a super-white surface layer;

[0083] (3) Preparation of a gray light-absorbing support layer

[0084] The PET resin, solvent black 3, light-absorbing filler, silicon dioxide and antioxidant 1076 are uniformly mixed, and the slurry is flow cast on the upper surface of the super-white surface layer in the mold of step (2) to obtain a gray light-absorbing support layer, and a super-white surface layer is formed on the upper surface of the gray light-absorbing support layer by repeating step (2); the composite film is placed on a quenching rod for cooling, and bidirectional stretching is performed.

[0085] Example 3

[0086] A double-sided printing ultra-low light transmission polyester-based film is composed of a three-layer composite, wherein the middle layer is a gray light-absorbing support layer, and the gray light-absorbing support layer is flanked by super-white surface layers with the same thickness; the gray light-absorbing support layer accounts for 63% of the total thickness;

[0087] The super-white surface layer is prepared from the following raw materials in parts by mass:

[0088] 77 parts of PET resin, 2 parts of light-absorbing filler, 6 parts of superfine calcium carbonate, 0.35 parts of stearic acid amide, 0.12 parts of oleic acid amide and 0.89 parts of zinc oxide; the particle size of the superfine calcium carbonate is 90 nm;

[0089] The gray light-absorbing support layer is prepared from the following raw materials:

[0090] 89 parts of PET resin, 0.15 parts of solvent black 3, 2.4 parts of light-absorbing filler, 1.5 parts of silicon dioxide and 0.089 parts of antioxidant 1076 are uniformly mixed;

[0091] The light-absorbing filler is prepared from 1.3 parts of silicon nitride, 1.2 parts of zirconium oxide, 1.6 parts of titanium oxide, 1.2 parts of silicon nitride magnesium, 4.9 parts of aluminum oxide, 0.37 parts of yttrium trioxide, 0.13 parts of lanthanum oxide, 0.28 parts of cerium oxide and 11.3 parts of carbon nanotubes;

[0092] The preparation method of the double-sided printing ultra-low light transmission polyester-based film is as follows:

[0093] (1) Preparation of light-absorbing filler

[0094] A raw material preparation

[0095] Silicon nitride, zirconium oxide, titanium oxide, silicon nitride magnesium, aluminum oxide, yttrium trioxide, lanthanum oxide, cerium oxide and carbon nanotubes are prepared;

[0096] B raw material mixing

[0097] Mixing lanthanum oxide and cerium oxide, adding 23 times of pure water in mass, adding hydrochloric acid solution into the pure water to dissolve the lanthanum oxide and cerium oxide, adding silicon nitride and carbon nanotubes into the solution, stirring at a speed of 78 r / min, and gradually adding sodium hydroxide solution until no precipitate is generated in the solution to stop adding the sodium hydroxide solution;

[0098] Filtering the solution, washing the precipitate with pure water for 3 times, and drying for standby use;

[0099] The mass fraction of the hydrochloric acid solution is 19%; the mass fraction of the sodium hydroxide solution is 37%;

[0100] C ball milling

[0101] Mixing the mixture obtained in the previous step with zirconium oxide, titanium oxide, silicon nitride magnesium, aluminum oxide and yttrium trioxide, adding 1 times of ethanol solution in mass of all materials into a ball mill, ball milling for 18 h; adding 19% of a binder in mass of the ethanol solution into the ball mill, ball milling for 5 h;

[0102] The binder is mixed by polyvinyl alcohol and calcium cellulose at a mass ratio of 1:0.12; the volume fraction of ethanol in the ethanol solution is 69%;

[0103] D sintering

[0104] Granulating the slurry obtained in the previous step in a spray drying device, drying at 100 DEG C for 4 h, calcining at a temperature of 2100 DEG C under protection of argon for 7 h to obtain the light-absorbing filler;

[0105] (2) preparing an ultra-white surface layer

[0106] Mixing and melting PET resin, light-absorbing filler, ultra-fine calcium carbonate, stearic acid amide, oleic acid amide and zinc oxide, pouring into a mold to flow and form a film after mixing the materials by extrusion for multiple times to obtain an ultra-white surface layer;

[0107] (3) preparing a gray light-absorbing support layer

[0108] Mixing PET resin, solvent black 3, light-absorbing filler, silicon dioxide and antioxidant 1076 uniformly, flowing the slurry on the surface of the ultra-white surface layer in the mold in step (2) to obtain a gray light-absorbing support layer, and repeatedly forming an ultra-white surface layer on the surface of the gray light-absorbing support layer; placing the composite film on a quenching rod to cool and performing bidirectional stretching.

[0109] To verify the effect of the application, the following comparative examples are set up:

[0110]

[0111] Experimental example

[0112] The base films were prepared according to Examples 1-3 and Comparative Examples 1-5 respectively, the tensile strength was detected according to GB / T 1040.3, the haze was detected according to GB / T 2410, the light transmittance of each group of films was analyzed by using ultraviolet-visible spectrophotometer, and the scanning wavelength was 200-800 nm.

[0113] The results are as follows:

[0114] Tensile strength TD (MPa) Haze % Transmittance % Example 1 247.09 0.87 6.34 Example 2 238.65 0.91 5.58 Example 3 251.39 0.78 4.67 Comparative Example 1 211.04 0.88 6.94 Comparative Example 2 204.99 0.75 9.79 Comparative Example 3 199.05 0.90 9.09 Comparative Example 4 187.01 0.79 7.77 Comparative Example 5 219.39 0.71 8.33

[0115] As can be seen from the table, the base film prepared by the application has higher tensile strength while ensuring the haze, has low light transmittance, and has higher adaptability to the use environment of the printed film. Comparative Example 1 lacks ion adsorption in the solution due to the lack of mixing treatment of the light-absorbing filler, has poor uniformity, affects the dispersion of carbon fibers and rare earth elements in the film, and affects the particle formation, resulting in poor overall film structure, low strength, and high light transmittance. Comparative Examples 2-4 lack rare earth elements, although the haze is not significantly affected, the strength and low light transmittance are significantly decreased; in Comparative Example 5, the adhesion agent lacks the adsorption mineralization effect of calcium cellulose, the particle formation of the filler is affected, resulting in a weaker overall use effect of the film than the examples.

Claims

1. A double-sided printed ultra-low transmission polyester-based film, characterized in that, The film is composed of three layers of composite, the middle layer is a gray light-absorbing support layer, the same thickness of super white surface layer on both sides of the gray light-absorbing support layer; the super white surface layer is prepared from the following raw materials by mass fraction: 75-78 parts of PET resin, 1-2 parts of light-absorbing filler, 5-7 parts of superfine calcium carbonate, 0.3-0.5 parts of stearic acid amide, 0.1-0.2 parts of oleic acid amide, 0.8-0.9 parts of zinc oxide; the particle size of the superfine calcium carbonate is 80-100 nm; The gray light-absorbing support layer is prepared from the following raw materials: 88-91 parts of PET resin, 0.1-0.15 parts of solvent black 3, 2-4 parts of light-absorbing filler, 1-1.5 parts of silicon dioxide, 0.08-0.09 parts of antioxidant 1076; The light-absorbing filler is prepared from 8-13 parts of structural ceramic material, 11-13 parts of carbon nanotube, 0.6-0.8 parts of rare earth oxide; the structural ceramic material is composed of 1-3 parts of silicon nitride, 1-2 parts of zirconium oxide, 1-1.6 parts of titanium oxide, 1-2 parts of silicon nitride magnesium, 4-9 parts of aluminum oxide; the rare earth oxide is composed of 0.3-0.7 parts of yttrium trioxide, 0.1-0.3 parts of lanthanum oxide, 0.2-0.28 parts of cerium oxide; the gray light-absorbing support layer accounts for 60-63% of the total thickness; The preparation method of the double-sided printing ultra-low light transmission polyester-based film is as follows: (1) Preparation of light-absorbing filler A raw material preparation By mass fraction, 1-3 parts of silicon nitride, 1-2 parts of zirconium oxide, 1-1.6 parts of titanium oxide, 1-2 parts of silicon nitride magnesium, 4-9 parts of aluminum oxide, 0.3-0.7 parts of yttrium trioxide, 0.1-0.3 parts of lanthanum oxide, 0.2-0.28 parts of cerium oxide, 11-13 parts of carbon nanotube are prepared; B raw material mixing Mix lanthanum oxide and cerium oxide, add 20-25 times the mass of pure water, drop hydrochloric acid solution into the pure water to dissolve lanthanum oxide and cerium oxide, add silicon nitride and carbon nanotube to the dissolved solution, stir at a speed of 70-80 r / min, and gradually drop sodium hydroxide solution until no precipitate is produced in the solution to stop dropping sodium hydroxide; Filter the solution, wash the precipitate with pure water for 3-5 times, and dry for use; C ball milling Mix the mixture obtained in the previous step with zirconium oxide, titanium oxide, silicon nitride magnesium, aluminum oxide, yttrium trioxide, add 1-2 times the mass of ethanol solution of all materials into the ball mill, ball mill for 13-18 h; add adhesive in the ball mill, ball mill for 5-8 h; the adhesive is prepared by mixing polyvinyl alcohol and calcium cellulose in a mass ratio of 1:0.1-0.13; D sintering Granulate the slurry obtained in the previous step in a spray drying device, dry at 100-150℃ for 2-4h, under argon protection, calcination temperature is 2100℃-2300℃, calcination time is 6-7h, the light-absorbing filler can be obtained; (2) Preparation of super white surface layer With mass parts, 75-78 parts of PET resin, 1-2 parts of light absorbing filler, 5-7 parts of superfine calcium carbonate, 0.3-0.5 parts of stearic acid amide, 0.1-0.2 parts of oleic acid amide, 0.8-0.9 parts of zinc oxide are mixed and melted, and after the material is extruded and mixed several times, it is poured into a mold to flow into a film, obtaining a super-white surface layer; (3) Preparation of gray light-absorbing support layer With mass parts, 88-91 parts of PET resin, 0.1-0.15 parts of solvent black 3, 2-4 parts of light absorbing filler, 1-1.5 parts of silicon dioxide, 0.08-0.09 parts of antioxidant 1076 are uniformly mixed, and the slurry is cast on the surface of the super-white surface layer in the mold of step (2) to obtain a gray light-absorbing support layer. Continue to repeat step (2) to form a super-white surface layer on the surface of the gray light-absorbing support layer; Put the composite film on the quenching rod to cool, and stretch it in two directions.

2. The double-sided printed ultra-low transmission polyester-based film according to claim 1, wherein, The mass fraction of the hydrochloric acid solution is 17-20%.

3. The double-sided printed ultra-low transmission polyester-based film according to claim 1, wherein, The volume fraction of ethanol in the ethanol solution is 66-73%.

4. The double-sided printed ultra-low transmission polyester-based film according to claim 1, wherein, The amount of the adhesive is 15-19% of the mass of the ethanol solution.

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