CN117601536A - High-rigidity thin optical polyester film and preparation method thereof - Google Patents

Abstract

The invention belongs to the technical field of polyester films, and relates to a high-rigidity thin optical polyester film and a preparation method thereof, wherein the high-rigidity thin optical polyester film comprises a layer B and layers A positioned on two sides of the layer B, and the whole is in an ABA superposition structure; wherein, the preparation raw materials of the layer B comprise: 5-10% by mass of modified copolyester and the balance of pure polyester; the preparation raw materials of the layer A comprise: 3-5% of UV blocking master batch, 5-10% of opening agent master batch and the balance of pure polyester; the modified copolyester is prepared from a diol mixture and dibasic acid through esterification and polycondensation reaction; the molar ratio of the diol mixture to the dibasic acid (1.2-1.28) is 1; the diol mixture consists of an anthracene group-containing diol and ethylene glycol, the molar ratio of the anthracene group-containing diol to the ethylene glycol being (1:9) - (3:7). The high-rigidity thin optical polyester film prepared by the application has the characteristics of high light transmittance, low haze, high rigidity and the like.

Description

High-rigidity thin optical polyester film and preparation method thereof

Technical Field

The invention belongs to the technical field of polyester films, and relates to a high-rigidity thin optical polyester film and a preparation method thereof.

Background

Polyethylene terephthalate (PET) is one of thermoplastic polyesters, has good wear resistance, high light transmittance and electrical insulation, can be processed in different modes, and can be used in different fields such as spinning, engineering plastics, films and the like. The polyester film is prepared by melt co-extrusion biaxial stretching of polyethylene terephthalate material, and is widely used in the fields of electronics, display, protection and the like due to good mechanical property, thermal property, electrical insulation property and optical property. With the demand for product thickness reduction and weight reduction in the fields of electronics, display, protection, etc., weight reduction and thickness reduction technologies of optical polyester films and product development have been paid attention in recent years.

An important characteristic of thin optical polyester films is the requirement for high light transmittance and low haze, and in order to ensure high light transmittance and low haze of the product, it is generally necessary to not add inorganic particles to the core layer of the polyester film during the production process that affect the light transmittance and haze. The effects thereby result are: the lack of inorganic particles capable of serving as nucleating agents in the polyester film is characterized in that the crystallinity of the film formed after biaxial stretching is insufficient, the film has insufficient rigidity, when the downstream processing is heated again, the polyester film is easy to generate the problems of warping, unevenness, intolerance to temperature and the like, the use of products is affected, and the film is particularly obvious in the thin optical polyester film smaller than 30 microns.

Aiming at the problem of insufficient rigidity of the thin optical polyester film, the prior technical proposal for solving the problem of the prior technical personnel is as follows: 1. the crystallinity of the PET material is increased by improving the process temperature in the biaxial stretching process, and the rigidity of the product is improved. 2. And (3) carrying out functional coating treatment on the surface of the polyester film, and improving the integral rigidity of the film by utilizing the self high rigidity characteristic of the coated material.

Although the technicians have made a great deal of research on improving the rigidity of the thin optical polyester film, the existing technical solutions for solving the problem of insufficient rigidity of the thin optical polyester film still have a lot of defects: 1. the process temperature in the biaxial stretching process can be increased by a certain degree of crystallinity, but the increase range is limited, the requirement of improving the rigidity of the product is not met, and the phenomenon of uneven film surface of the film caused by overhigh temperature is easily caused by increasing the process temperature. 2. The polyester film surface is subjected to functional coating treatment, so that the rigidity of the film is limited, and the problems of poor coating appearance, low yield, high cost, low universality and the like are easy to occur in the coating process.

Disclosure of Invention

The invention provides a high-rigidity thin optical polyester film and a preparation method thereof, which are used for overcoming the defects of the prior art. The problems of warping, unevenness, intolerance of temperature and the like of the thin optical polyester film in the downstream processing and using process are greatly reduced, and the product can be widely applied to the fields of high-end protection/release, window film, MLCC release film and the like.

The technical scheme adopted for solving the technical problems is as follows: a high-rigidity thin optical polyester film comprises a layer B and layers A positioned on two sides of the layer B, and the whole is in an ABA superposition structure;

wherein, the preparation raw materials of the layer B comprise: 5-10% by mass of modified copolyester and the balance of pure polyester;

the preparation raw materials of the layer A comprise: 3-5% of UV blocking master batch, 5-10% of opening agent master batch and the balance of pure polyester;

the modified copolyester is prepared from a diol mixture and dibasic acid through esterification and polycondensation reaction; the molar ratio of the diol mixture to the diacid is (1.2-1.28): 1, a step of;

the diol mixture consists of an anthracene group-containing diol and ethylene glycol, the molar ratio of the anthracene group-containing diol to the ethylene glycol being (1:9) - (3:7).

As an improved technical scheme of the application, the dibasic acid is aromatic diacid.

As an improved technical scheme of the application, the diol containing anthracene groups is one of 1, 4-anthracene diol, 9-anthracene methanol or 2-amyl-9, 10-anthracene diol.

As an improved technical scheme of the application, the UV blocking master batch is capable of blocking the wave band below 350nm and transmitting the wave band above 350 nm.

As an improved technical scheme of the application, the opening agent master batch consists of pure polyester and silicon dioxide particles, wherein the content of the silicon dioxide particles is 0.3% -1.5% of the weight of the opening agent master batch, and the silicon dioxide particle size is as follows: 1.0-2.0 μm.

As an improved technical scheme of the application, the thickness of the polyester film is 6-50 mu m.

As an improved technical scheme of the application, the thickness of the A layer of the polyester film is independently 1-2 mu m.

Another object of the present application is to provide a method for preparing a high-rigidity thin optical polyester film, comprising the steps of:

step 1: adding pure polyester, UV blocking master batch and opening agent master batch according to the proportioning amount in an extruder I for melt extrusion; adding pure polyester and modified copolyester in the extruder II according to the proportion, and carrying out melt extrusion;

step 2: feeding the melt extruded by the extruder I into an A layer in a three-layer die head of an ABA structure; feeding the melt extruded by the extruder II into a layer B in a three-layer die of an ABA structure; the melt of the layer A and the melt of the layer B flow out together according to the thickness proportion; the high-rigidity thin optical polyester film is obtained through casting, longitudinal drawing, transverse drawing, shaping, cooling, UV irradiation and rolling.

As an improved technical scheme of the application, the wavelength of the UV irradiation is 365nm, the power of the UV irradiation is 160-200w, and the time of the UV irradiation is 2-5 seconds.

The beneficial effects are that:

1. the invention adopts the main thickness layer of the thin optical polyester film: the modified copolyester containing anthracene groups is added into the layer B, and the anthracene groups in the modified copolyester are subjected to ring forming reaction by virtue of the good co-solubility and uniform distribution of the modified copolyester and pure polyester and the UV irradiation of specific wavelength after biaxial stretching and cooling, so that a uniform and fine three-dimensional network structure is formed in the layer B material, and the rigidity of the thin optical polyester film is improved.

2. The invention adopts the main thickness layer of the thin optical polyester film: inorganic particles which are beneficial to providing crystallization nucleating agents are not added in the layer B, so that the decrease of the light transmittance and the increase of the haze of the film caused by reflection, refraction, scattering and the like of the inorganic particles on transmitted light are avoided, and excellent optical performance is also achieved while good rigidity is ensured.

3. The invention adopts the method that the outer surface layer of the thin optical polyester film is laminated with: the Ultraviolet (UV) blocking master batch which can block the wave band below 350nm and simultaneously transmit the wave band above 350nm is added in the layer A, so that the problem that the ring-formed anthracene group is subject to decyclization due to the ultraviolet radiation of the wave band less than 350nm in natural light can be avoided.

In conclusion, the rigidity of the polyester film is greatly improved, the convenience in downstream processing of the polyester film and the deformation resistance when the polyester film is heated again are improved, and the problems of warping, unevenness, intolerance to temperature and the like are effectively reduced.

Detailed Description

In order that the invention may be readily understood, a more particular description of the invention will be rendered by reference to specific embodiments that are illustrated below. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

The thin optical polyester film provided by the invention comprises a layer B (middle layer) and layers A (surface layers) positioned on two sides of the layer B. The modified copolyester containing the anthracene group is added into the B layer, so that the B layer material forms a uniform and fine three-dimensional network structure in the B layer through the cyclization reaction of the anthracene group under the irradiation of UV with specific wavelength without adding inorganic particles, and the rigidity of the thin optical polyester film is improved. And the Ultraviolet (UV) blocking master batch which can block the wave band below 350nm and simultaneously transmit the wave band above 350nm is added in the layer A, so that the problem that the ring-formed anthracene group is subject to ring-opening due to the ultraviolet radiation of the wave band less than 350nm in natural light is avoided. B layer and A layer are cast into a sheet on a film production line through melt multi-layer coextrusion, and then are subjected to longitudinal drawing, transverse drawing, shaping and cooling; and (3) through Ultraviolet (UV) irradiation of a specific wavelength, forming a uniform and fine three-dimensional network structure in the layer B through cyclization reaction of anthracene groups under the UV irradiation of the specific wavelength, and then rolling to form a film. The polyester film manufactured by the structural design has higher overall rigidity, improves the convenience in downstream processing of the polyester film and the deformation resistance when being heated again, has excellent optical performance, and cannot be realized by the conventional polyester film.

In the production process of a thin polyester film, a certain amount of small-particle-size inorganic particles are required to be added into a core layer to serve as a nucleating agent in order to improve the rigidity of the product, so that the crystallization effect of the core layer which occupies the main thin component is improved. However, the external inorganic particles can have adverse effects on optical properties such as light transmittance, haze and definition of the polyester film, and the three-dimensional network structure formed by the light cyclization reaction of the copolyester containing anthracene groups can replace an inorganic particle nucleating agent, so that the decrease of the light transmittance and the increase of the haze of the film caused by reflection, refraction, scattering and the like of the transmitted light by the inorganic particles are avoided, and the excellent optical properties are also provided while the good rigidity is ensured.

In the invention, the layer B consists of 5-10% of modified copolyester containing anthracene groups and 90-95% of pure polyester by mass percent. Under the irradiation of long ultraviolet light wave (more than 300 nanometers), the anthracene group can undergo bimolecular [4+4] photo-cyclization reaction to form a dimer, the dimer ring is uniformly distributed in pure resin to form a cloud-gathered fine three-dimensional network structure, and the cloud-gathered fine three-dimensional network structure is tightly interwoven with pure polyester, so that the skeleton effect is achieved, the free activity capability of the pure polyester around the skeleton is slowed down, and the rigidity of the B layer is improved. However, when the content of the anthracene group-containing modified copolyester is too high, on the one hand, the overall color tone of the B layer may be changed, and on the other hand, the effect of the excessive three-dimensional network structure on improving the rigidity of the B layer tends to be saturated and the cost of the product may be significantly increased.

In the invention, the modified copolyester is formed by copolymerizing a diol mixture and a dibasic acid through esterification reaction and polycondensation reaction, and the molar ratio of the diol mixture to the dibasic acid is 1.2-1.28:1, more preferably 1.23-1.25:1. Too high a molar ratio can affect the diethylene glycol content of the copolyester, adversely affecting the heat resistance of the thin polyester film product to which the secondary copolyester is applied; too low a molar ratio may result in a decrease in the esterification efficiency and esterification rate, which is detrimental to product quality and production.

In the invention, the molar ratio of the anthracene group-containing glycol to the ethylene glycol in the glycol mixture is (1:9) - (3:7), and preferably the molar ratio of the anthracene group-containing glycol to the ethylene glycol in the glycol mixture is (1.5:8.5) - (2.5:7.5). The anthracene group-containing diol is one of 1,4 anthracene diol, 9-anthracene methanol or 2-amyl-9, 10-anthracene diol, and preferably the anthracene group-containing diol is 2-amyl-9, 10-anthracene diol. 2-amyl-9, 10-anthracenediol contains 2 hydroxyl groups and can more effectively form esterification crosslinking with terephthalic acid.

In the present invention, the dibasic acid may be a linear fatty diacid, but is mainly an aromatic diacid such as terephthalic acid, terephthaloic acid, terephthalic acid, etc., preferably terephthalic acid and terephthalic acid, more preferably terephthalic acid from the viewpoint of economy.

In the invention, the layer A consists of 3-5% of UV blocking master batch, 5-10% of opening agent master batch and pure polyester according to mass percentage.

Dimers formed by cyclization of anthracene groups are prone to depolymerization under short ultraviolet light waves (< 300 nm) to generate original anthracene groups. In order to avoid the three-dimensional network structure in the B layer of the high-rigidity thin optical polyester film product in the use process, a UV blocking master batch capable of blocking the wave band below 350nm and transmitting the wave band above 350nm is added to 2 outer surface layers (A layers) of the B layer, so that the ring-formed anthracene group is prevented from being decyclized due to the UV irradiation of the wave band below 350nm in the natural light. The ultraviolet band below 350nm can be fully blocked in the layer A by adding 3-5% of the UV blocking master batch, but the UV blocking master batch has a certain color, and the color tone of the thin optical polyester film product can be influenced when the UV blocking master batch is excessively added.

In the production process of the polyester film, a certain amount of opening agent master batch is required to be added into the surface layer to improve the smoothness of the film surface, so that scratches on the surface of the roller are avoided. The active ingredients of the common opening agent master batch are mainly inorganic particles such as silicon dioxide, calcium carbonate, barium sulfate and the like.

In the invention, the master batch of the opening agent consists of pure polyester and silicon dioxide particles, wherein the content of the silicon dioxide particles is 0.3-1.5 percent, preferably 0.3 percent, of the weight of the master batch of the opening agent; the average particle diameter of the silica particles is 1.0-2.0 μm, preferably 1.0-1.5 μm, and the specific silica particle content and particle diameter can be determined according to the different light transmittance, haze and surface roughness requirements of the polyester film.

In the invention, the pure polyesters in the layer A and the layer B can be different polyesters or the same polyester, but the polyesters are all polymers of dibasic acid and dihydric alcohol. In the present invention, the thickness of the polyester film is 6 to 50. Mu.m, more preferably 6 to 38. Mu.m.

In the invention, the thickness of the layer A is independently 1-2 mu m. The thickness of the layer A is too low, so that the whole layer A is difficult to block ultraviolet light with the wave band below 350nm, and the thickness of the layer A is too thick, so that the whole light transmittance and the haze of the high-rigidity thin optical polyester film are affected.

The invention also provides a preparation method of the high-rigidity thin optical polyester film, which comprises the following steps:

step 1: adding pure polyester, UV blocking master batch and opening agent master batch in proportion into an extruder I for melt extrusion; adding pure polyester and modified copolyester in an extruder II in proportion for melt extrusion.

Step 2: and (3) conveying the melt extruded by the extruder I into an A layer in a three-layer die head of the ABA structure, conveying the melt extruded by the extruder II into a B layer in a three-layer die head of the ABA structure, discharging the melt of the A layer and the melt of the B layer together according to the occupied thickness proportion, and obtaining the high-rigidity thin optical polyester film through casting, longitudinal drawing, transverse drawing, shaping, cooling, UV irradiation and winding.

Step 1: adding pure polyester, UV blocking master batch and opening agent master batch in proportion into an extruder I, and carrying out melt extrusion at a temperature of 276-286 ℃; adding pure polyester and modified copolyester in proportion into an extruder II, and carrying out melt extrusion at the temperature of 276-286 ℃.

Step 2: and (3) conveying the melt extruded by the extruder I into an A layer in a three-layer die head of the ABA structure, conveying the melt extruded by the extruder II into a B layer in a three-layer die head of the ABA structure, discharging the melt of the A layer and the melt of the B layer together according to the occupied thickness proportion, and obtaining the high-rigidity thin optical polyester film through casting, longitudinal drawing, transverse drawing, shaping, cooling, UV irradiation and winding.

Wherein, (1) the cast sheet is longitudinally stretched, and the longitudinal stretching ratio is 3.0-4.0.

(2) And transversely stretching the longitudinal pull-tab, wherein the transverse stretching ratio is 3.3-4.5.

(3) And (3) carrying out heat setting on the stretched film, wherein the heat setting temperature is 225-245 ℃.

(4) And cooling the shaped film at 40-120 ℃.

(5) And (3) carrying out UV irradiation on the cooled film, wherein the irradiation power is 160-200W.

(6) And rolling the film after UV irradiation to obtain the high-rigidity thin optical polyester film.

It should be noted that: the longitudinal stretching ratio, the transverse stretching ratio, the heat setting temperature and the UV irradiation power involved in the preparation method can be properly adjusted according to different product requirements by technicians, including but not limited to the parameter conditions set forth in the invention.

The polyester film prepared according to the method comprises the following specific testing method:

thickness: tested according to GB/T33399-2016.

Optical properties: the test was carried out according to ASTM D1003 (instrument model: BYK-4725) (T: light transmittance, H: haze).

Rigidity: under the condition of ensuring the flatness of the polyester film, taking a 15mm multiplied by 160mm long polyester film sample in the MD direction (longitudinal direction: longitudinal stretching direction), horizontally placing, wherein the clamping length is 20mm, taking the horizontal position difference value between the free end and the clamping end as an evaluation standard of the rigidity of the polyester film, and indicating that the rigidity of the polyester film is higher when the horizontal position difference value is smaller.

Temperature resistance: a polyester film roll sample with the width of 1260mm passes through an oven with the length of 32m and the environmental temperature of 160 ℃ at the speed of 40m/min under the traction tension of 15N/m, and then the surface evenness of the polyester film is observed, the evenness is good, the better the temperature resistance of the polyester film is, "goodthe O" indicates that the temperature resistance is excellent; "DeltaV" represents that the temperature resistance is general; "×" indicates poor temperature resistance.

Appearance: the polyester film was cut out to obtain a final product having a width of 1 m and a length of 1 m, and the appearance was carefully observed using a strong light flashlight (model: RJW7102A/LT, ocean King Lighting technologies Co., ltd.). Apparent no scratch/rub or 1 very light scratch/gift is seen, but indeterminate, mark "; apparent scratch/scratch is obviously observed, the (quantity) is less than or equal to 5, and the delta is recorded; the whole surface is obviously scratched and rubbed, and marked by X.

In order that the invention may be readily understood, a more particular description of the invention will be rendered by reference to specific embodiments that are illustrated below. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

Example 1

Preparation of modified copolyester:

according to the mole ratio of the diol mixture to terephthalic acid of 1.25:1, the molar ratio of 9-anthracene methanol to ethylene glycol in the glycol mixture is 10:90; the usual catalysts: the adding amount of ethylene glycol antimony is 200ppm; commonly used stabilizers: adding triphenyl phosphate with the addition amount of 20ppm, uniformly mixing the triphenyl phosphate, adding the mixture into a polyester synthesis reaction kettle, carrying out esterification reaction under the protection of nitrogen, wherein the temperature in the kettle is 220-260 ℃, the initial pressure in the kettle is 0.15-0.2MP, and carrying out pressure relief when the esterification rate reaches 96%, so as to complete the esterification reaction; after the esterification reaction is finished, removing excessive diol mixture, and polycondensing for 3.5 hours at 280-290 ℃ under 130Pa environment to obtain the modified copolyester.

Adding polyethylene terephthalate, UV blocking master batch and opening agent master batch in proportion into an extruder I, and carrying out melt extrusion; adding polyethylene terephthalate and modified copolyester in proportion into an extruder II, and carrying out melt extrusion. The melt extruded by extruder I was fed into the A layer in the three layer die of the ABA structure and the melt extruded by extruder II was fed into the B layer in the three layer die of the ABA structure.

The extruder I and the extruder II synchronously extrude and synchronously guide into a T-shaped die head. In the T-shaped die head, the melt of the extruder I is evenly distributed to two sides of the melt of the extruder II, and two groups of melts are laminated and combined according to an A/B/A three-layer structure and flow on a rotating casting sheet cooling drum with the surface temperature of 20 ℃ to obtain laminated casting sheets. Preheating the laminated casting film at 70-85 ℃, rapidly stretching the laminated casting film longitudinally (in the length direction) for 3.5 times by utilizing the difference of the rotation speeds of two rollers under the infrared heating condition, and gradually cooling the laminated casting film at 30-60 ℃ to obtain the longitudinally stretched film. Clamping two sides of a longitudinal drawing film by a clamp, sending the longitudinal drawing film into a transverse drawing box, preheating at 90-115 ℃, continuously and repeatedly stretching the longitudinal drawing film for 3.8 times along the transverse direction (width direction) at 110-130 ℃, carrying out heat treatment and shaping for 7-15s at 240 ℃, cooling at 40 ℃, carrying out traction and winding after UV irradiation with the wavelength of 365nm and the power of 160w for 2 seconds, and obtaining the high-rigidity thin optical polyester film with the thickness of 38 mu m, wherein the thickness of a layer A is 2.0 mu m.

In this example:

the layer A is prepared from the following raw materials: 3 parts by weight of UV blocking master batch capable of blocking a wave band below 350nm, 8 parts by weight of opening agent master batch and 89 parts by weight of polyethylene terephthalate.

The raw materials of the layer B are as follows: 5 parts by weight of modified copolyester and 95 parts by weight of polyethylene terephthalate.

Wherein, the weight content of the silicon dioxide particles in the master batch of the opening agent is 0.5 percent, and the particle size is 2.0 mu m.

Example 2

Preparation of modified copolyester:

according to the mole ratio of the diol mixture to terephthalic acid of 1.2:1, the molar ratio of 2-amyl-9, 10-anthracenediol to ethylene glycol in the diol mixture is 1:9, a step of performing the process; the usual catalysts: the adding amount of ethylene glycol antimony is 200ppm; commonly used stabilizers: adding triphenyl phosphate with the addition amount of 20ppm, uniformly mixing the triphenyl phosphate, adding the mixture into a polyester synthesis reaction kettle, carrying out esterification reaction under the protection of nitrogen, wherein the temperature in the kettle is 220-260 ℃, the initial pressure in the kettle is 0.15-0.2MP, and carrying out pressure relief when the esterification rate reaches 96%, so as to complete the esterification reaction; after the esterification reaction is finished, removing excessive diol mixture, and polycondensing for 3.5 hours at 280-290 ℃ under 130Pa environment to obtain the modified copolyester.

Adding polyethylene terephthalate, UV blocking master batch and opening agent master batch in proportion into an extruder I, and carrying out melt extrusion; adding polyethylene terephthalate and modified copolyester in proportion into an extruder II, and carrying out melt extrusion. The melt extruded by extruder I was fed into the A layer in the three layer die of the ABA structure and the melt extruded by extruder II was fed into the B layer in the three layer die of the ABA structure.

The extruder I and the extruder II synchronously extrude and synchronously guide into a T-shaped die head. In the T-shaped die head, the melt of the extruder I is evenly distributed to two sides of the melt of the extruder II, and two groups of melts are laminated and combined according to an A/B/A three-layer structure and flow on a rotating casting sheet cooling drum with the surface temperature of 20 ℃ to obtain laminated casting sheets. Preheating the laminated casting film at 70-85 ℃, rapidly stretching the laminated casting film longitudinally (in the length direction) for 3.5 times by utilizing the difference of the rotation speeds of two rollers under the infrared heating condition, and gradually cooling the laminated casting film at 30-60 ℃ to obtain the longitudinally stretched film. Clamping two sides of a longitudinal drawing film by a clamp, sending the longitudinal drawing film into a transverse drawing box, preheating at 90-115 ℃, continuously and repeatedly stretching the longitudinal drawing film for 3.8 times along the transverse direction (width direction) at 110-130 ℃, carrying out heat treatment and shaping for 7-15s at 240 ℃, cooling at 100 ℃, carrying out traction and winding after UV irradiation with the wavelength of 365nm and the power of 160w for 2 seconds, and obtaining the high-rigidity thin optical polyester film with the thickness of 12 mu m, wherein the thickness of a layer A is 1.0 mu m.

In this example:

the layer A is prepared from the following raw materials: 5 parts by weight of UV blocking master batch capable of blocking a wave band below 300nm, 10 parts by weight of opening agent master batch and 85 parts by weight of polyethylene terephthalate.

The raw materials of the layer B are as follows: 5 parts by weight of modified copolyester and 95 parts by weight of polyethylene terephthalate.

Wherein the content of silica particles in the master batch of the opening agent is 0.3 percent, and the particle size is 1.5 mu m.

Example 3

Preparation of modified copolyester:

according to the mole ratio of the diol mixture to terephthalic acid of 1.2:1, the molar ratio of 1,4 anthracene diol to ethylene glycol in the diol mixture is 2:8, a common catalyst: ethylene glycol antimony is added in an amount of 200ppm, a common stabilizer: adding triphenyl phosphate with the addition amount of 20ppm, uniformly mixing the triphenyl phosphate, adding the mixture into a polyester synthesis reaction kettle, carrying out esterification reaction under the protection of nitrogen, wherein the temperature in the kettle is 220-260 ℃, the initial pressure in the kettle is 0.15-0.2MP, and carrying out pressure relief when the esterification rate reaches 96%, so as to complete the esterification reaction; after the esterification reaction is finished, removing excessive diol mixture, and polycondensing for 3.5 hours at 280-290 ℃ under 130Pa environment to obtain the modified copolyester.

Adding polyethylene terephthalate, UV blocking master batch and opening agent master batch in proportion into an extruder I, and carrying out melt extrusion; adding polyethylene terephthalate and modified copolyester in proportion into an extruder II, and carrying out melt extrusion. The melt extruded by extruder I was fed into the A layer in the three layer die of the ABA structure and the melt extruded by extruder II was fed into the B layer in the three layer die of the ABA structure.

The extruder I and the extruder II synchronously extrude and synchronously guide into a T-shaped die head. In the T-shaped die head, the melt of the extruder I is evenly distributed to two sides of the melt of the extruder II, and two groups of melts are laminated and combined according to an A/B/A three-layer structure and flow on a rotating casting sheet cooling drum with the surface temperature of 20 ℃ to obtain laminated casting sheets. Preheating the laminated casting film at 70-85 ℃, rapidly stretching the laminated casting film longitudinally (in the length direction) for 3.5 times by utilizing the difference of the rotation speeds of two rollers under the infrared heating condition, and gradually cooling the laminated casting film at 30-60 ℃ to obtain the longitudinally stretched film. Clamping two sides of a longitudinal drawing film by a clamp, sending the longitudinal drawing film into a transverse drawing box, preheating at 90-115 ℃, continuously and repeatedly stretching the longitudinal drawing film for 3.8 times along the transverse direction (width direction) at 110-130 ℃, carrying out heat treatment and shaping for 7-15s at 240 ℃, cooling at 60 ℃, carrying out traction and winding after UV irradiation with the wavelength of 365nm and the power of 200w for 3 seconds, and obtaining the high-rigidity thin optical polyester film with the thickness of 25 mu m, wherein the thickness of a layer A is 1.5 mu m.

In this example:

the layer A is prepared from the following raw materials: 5 parts by weight of UV blocking master batch capable of blocking a wave band below 350nm, 5 parts by weight of opening agent master batch and 90 parts by weight of polyethylene terephthalate.

The raw materials of the layer B are as follows: 8 parts by weight of modified copolyester and 92 parts by weight of polyethylene terephthalate.

Wherein the content of silica particles in the master batch of the opening agent is 0.3 percent, and the particle size is 2.0 mu m.

Example 4

Preparation of modified copolyester:

according to the molar ratio of the diol mixture to terephthalic acid of 1.23: the molar ratio of 2-pentyl-9, 10-anthracenediol to ethylene glycol in the diol mixture was 1.5:8.5, usual catalysts: ethylene glycol antimony is added in an amount of 200ppm, a common stabilizer: adding triphenyl phosphate with the addition amount of 20ppm, uniformly mixing the triphenyl phosphate, adding the mixture into a polyester synthesis reaction kettle, carrying out esterification reaction under the protection of nitrogen, wherein the temperature in the kettle is 220-260 ℃, the initial pressure in the kettle is 0.15-0.2MP, and carrying out pressure relief when the esterification rate reaches 96%, so as to complete the esterification reaction; after the esterification reaction is finished, removing excessive diol mixture, and polycondensing for 3.5 hours at 280-290 ℃ under 130Pa environment to obtain the modified copolyester.

Adding polyethylene terephthalate, UV blocking master batch and opening agent master batch in proportion into an extruder I, and carrying out melt extrusion; adding polyethylene terephthalate and modified copolyester in proportion into an extruder II, and carrying out melt extrusion. The melt extruded by extruder I was fed into the A layer in the three layer die of the ABA structure and the melt extruded by extruder II was fed into the B layer in the three layer die of the ABA structure.

The extruder I and the extruder II synchronously extrude and synchronously guide into a T-shaped die head. In the T-shaped die head, the melt of the extruder I is evenly distributed to two sides of the melt of the extruder II, and two groups of melts are laminated and combined according to an A/B/A three-layer structure and flow on a rotating casting sheet cooling drum with the surface temperature of 20 ℃ to obtain laminated casting sheets. Preheating the laminated casting film at 70-85 ℃, rapidly stretching the laminated casting film longitudinally (in the length direction) for 3.5 times by utilizing the difference of the rotation speeds of two rollers under the infrared heating condition, and gradually cooling the laminated casting film at 30-60 ℃ to obtain the longitudinally stretched film. Clamping two sides of a longitudinal drawing film by a clamp, sending the longitudinal drawing film into a transverse drawing box, preheating at 90-115 ℃, continuously and repeatedly stretching the longitudinal drawing film for 3.8 times along the transverse direction (width direction) at 110-130 ℃, carrying out heat treatment and shaping for 7-15s at 240 ℃, cooling at 60 ℃, carrying out traction and winding after UV irradiation with the wavelength of 365nm and the power of 160w for 4 seconds, and obtaining the high-rigidity thin optical polyester film with the thickness of 38 mu m, wherein the thickness of a layer A is 1.5 mu m.

In this example:

the layer A is prepared from the following raw materials: 3 parts by weight of UV blocking master batch capable of blocking a wave band below 350nm, 8 parts by weight of opening agent master batch and 89 parts by weight of polyethylene terephthalate.

The raw materials of the layer B are as follows: 8 parts by weight of modified copolyester and 92 parts by weight of polyethylene terephthalate.

Wherein the content of silica particles in the master batch of the opening agent is 0.3 percent, and the particle size is 2.0 mu m.

Example 5

Preparation of modified copolyester:

according to the mole ratio of the diol mixture to terephthalic acid of 1.25:1, the molar ratio of 2-amyl-9, 10-anthracenediol to ethylene glycol in the diol mixture is 2:8, a common catalyst: ethylene glycol antimony is added in an amount of 200ppm, a common stabilizer: adding triphenyl phosphate with the addition amount of 20ppm, uniformly mixing the triphenyl phosphate, adding the mixture into a polyester synthesis reaction kettle, carrying out esterification reaction under the protection of nitrogen, wherein the temperature in the kettle is 220-260 ℃, the initial pressure in the kettle is 0.15-0.2MP, and carrying out pressure relief when the esterification rate reaches 96%, so as to complete the esterification reaction; after the esterification reaction is finished, removing excessive diol mixture, and polycondensing for 3.5 hours at 280-290 ℃ under 130Pa environment to obtain the modified copolyester.

Adding polyethylene terephthalate, UV blocking master batch and opening agent master batch in proportion into an extruder I, and carrying out melt extrusion; adding polyethylene terephthalate and modified copolyester in proportion into an extruder II, and carrying out melt extrusion. The melt extruded by extruder I was fed into the A layer in the three layer die of the ABA structure and the melt extruded by extruder II was fed into the B layer in the three layer die of the ABA structure.

The extruder I and the extruder II synchronously extrude and synchronously guide into a T-shaped die head. In the T-shaped die head, the melt of the extruder I is evenly distributed to two sides of the melt of the extruder II, and two groups of melts are laminated and combined according to an A/B/A three-layer structure and flow on a rotating casting sheet cooling drum with the surface temperature of 20 ℃ to obtain laminated casting sheets. Preheating the laminated casting film at 70-85 ℃, rapidly stretching the laminated casting film longitudinally (in the length direction) for 3.5 times by utilizing the difference of the rotation speeds of two rollers under the infrared heating condition, and gradually cooling the laminated casting film at 30-60 ℃ to obtain the longitudinally stretched film. Clamping two sides of a longitudinal drawing film by a clamp, sending the longitudinal drawing film into a transverse drawing box, preheating at 90-115 ℃, continuously and repeatedly stretching the longitudinal drawing film for 3.8 times along the transverse direction (width direction) at 110-130 ℃, carrying out heat treatment and shaping for 7-15s at 240 ℃, cooling at 60 ℃, carrying out traction and winding after UV irradiation with the wavelength of 365nm and the power of 180w for 4 seconds, and obtaining the high-rigidity thin optical polyester film with the thickness of 12 mu m, wherein the thickness of a layer A is 1.5 mu m.

In this example:

the layer A is prepared from the following raw materials: 4 parts by weight of UV blocking master batch capable of blocking a wave band below 350nm, 5 parts by weight of opening agent master batch and 91 parts by weight of polyethylene terephthalate.

The raw materials of the layer B are as follows: 10 parts by weight of modified copolyester and 90 parts by weight of polyethylene terephthalate.

Wherein the content of silica particles in the master batch of the opening agent is 0.3 percent, and the particle size is 1.5 mu m.

Example 6

Preparation of modified copolyester:

according to the mole ratio of the diol mixture to terephthalic acid of 1.24:1, the molar ratio of 9-anthracene methanol to ethylene glycol in the glycol mixture is 2.5:7.5, usual catalysts: ethylene glycol antimony is added in an amount of 200ppm, a common stabilizer: adding triphenyl phosphate with the addition amount of 20ppm, uniformly mixing the triphenyl phosphate, adding the mixture into a polyester synthesis reaction kettle, carrying out esterification reaction under the protection of nitrogen, wherein the temperature in the kettle is 220-260 ℃, the initial pressure in the kettle is 0.15-0.2MP, and carrying out pressure relief when the esterification rate reaches 96%, so as to complete the esterification reaction; after the esterification reaction is finished, removing excessive diol mixture, and polycondensing for 3.5 hours at 280-290 ℃ under 130Pa environment to obtain the modified copolyester.

Adding polyethylene terephthalate, UV blocking master batch and opening agent master batch in proportion into an extruder I, and carrying out melt extrusion; adding polyethylene terephthalate and modified copolyester in proportion into an extruder II, and carrying out melt extrusion. The melt extruded by extruder I was fed into the A layer in the three layer die of the ABA structure and the melt extruded by extruder II was fed into the B layer in the three layer die of the ABA structure.

The extruder I and the extruder II synchronously extrude and synchronously guide into a T-shaped die head. In the T-shaped die head, the melt of the extruder I is evenly distributed to two sides of the melt of the extruder II, and two groups of melts are laminated and combined according to an A/B/A three-layer structure and flow on a rotating casting sheet cooling drum with the surface temperature of 20 ℃ to obtain laminated casting sheets. Preheating the laminated casting film at 70-85 ℃, rapidly stretching the laminated casting film longitudinally (in the length direction) for 3.5 times by utilizing the difference of the rotation speeds of two rollers under the infrared heating condition, and gradually cooling the laminated casting film at 30-60 ℃ to obtain the longitudinally stretched film. Clamping two sides of a longitudinal drawing film by a clamp, feeding the longitudinal drawing film into a transverse drawing box, preheating at 90-115 ℃, continuously and repeatedly stretching the longitudinal drawing film for 3.8 times along the transverse direction (width direction) at 110-130 ℃, performing heat treatment and shaping for 7-15s at 240 ℃, cooling at 80 ℃, and performing traction rolling after 5 seconds of UV irradiation with the wavelength of 365nm and the power of 180w to obtain the high-rigidity thin optical polyester film with the thickness of 6 mu m, wherein the thickness of a layer A is 1 mu m.

In this example:

the layer A is prepared from the following raw materials: 5 parts by weight of UV blocking master batch capable of blocking a wave band below 350nm, 5 parts by weight of opening agent master batch and 90 parts by weight of polyethylene terephthalate.

The raw materials of the layer B are as follows: 10 parts by weight of modified copolyester and 90 parts by weight of polyethylene terephthalate.

Wherein the content of silica particles in the master batch of the opening agent is 0.3 percent, and the particle size is 1.0 mu m.

Example 7

Preparation of modified copolyester:

according to the molar ratio of the diol mixture to terephthalic acid of 1.26:1, the molar ratio of 1, 3-anthracene diol to ethylene glycol in the diol mixture is 3:7, a common catalyst: ethylene glycol antimony is added in an amount of 200ppm, a common stabilizer: adding triphenyl phosphate with the addition amount of 20ppm, uniformly mixing the triphenyl phosphate, adding the mixture into a polyester synthesis reaction kettle, carrying out esterification reaction under the protection of nitrogen, wherein the temperature in the kettle is 220-260 ℃, the initial pressure in the kettle is 0.15-0.2MP, and carrying out pressure relief when the esterification rate reaches 96%, so as to complete the esterification reaction; after the esterification reaction is finished, removing excessive diol mixture, and polycondensing for 3.5 hours at 280-290 ℃ under 130Pa environment to obtain the modified copolyester.

Adding polyethylene terephthalate, UV blocking master batch and opening agent master batch in proportion into an extruder I, and carrying out melt extrusion; adding polyethylene terephthalate and modified copolyester in proportion into an extruder II, and carrying out melt extrusion. The melt extruded by extruder I was fed into the A layer in the three layer die of the ABA structure and the melt extruded by extruder II was fed into the B layer in the three layer die of the ABA structure.

The extruder I and the extruder II synchronously extrude and synchronously guide into a T-shaped die head. In the T-shaped die head, the melt of the extruder I is evenly distributed to two sides of the melt of the extruder II, and two groups of melts are laminated and combined according to an A/B/A three-layer structure and flow on a rotating casting sheet cooling drum with the surface temperature of 20 ℃ to obtain laminated casting sheets. Preheating the laminated casting film at 70-85 ℃, rapidly stretching the laminated casting film longitudinally (in the length direction) for 3.5 times by utilizing the difference of the rotation speeds of two rollers under the infrared heating condition, and gradually cooling the laminated casting film at 30-60 ℃ to obtain the longitudinally stretched film. Clamping two sides of a longitudinal drawing film by a clamp, sending the longitudinal drawing film into a transverse drawing box, preheating at 90-115 ℃, continuously and repeatedly stretching the longitudinal drawing film for 3.8 times along the transverse direction (width direction) at 110-130 ℃, carrying out heat treatment and shaping for 7-15s at 240 ℃, cooling at 120 ℃, carrying out traction and winding after UV irradiation with the wavelength of 365nm and the power of 160w for 2 seconds, and obtaining the high-rigidity thin optical polyester film with the thickness of 6 mu m, wherein the thickness of a layer A is 1.0 mu m.

In this example:

the layer A is prepared from the following raw materials: 3 parts by weight of UV blocking master batch capable of blocking a wave band below 350nm, 5 parts by weight of opening agent master batch and 92 parts by weight of polyethylene terephthalate.

The raw materials of the layer B are as follows: 5 parts by weight of modified copolyester and 95 parts by weight of polyethylene terephthalate.

Wherein the content of silica particles in the master batch of the opening agent is 0.3 percent, and the particle size is 1.0 mu m.

Example 8

Preparation of modified copolyester:

according to the mole ratio of the diol mixture to terephthalic acid of 1.28:1, the molar ratio of 2-amyl-9, 10-anthracenediol to ethylene glycol in the diol mixture is 2:8, a common catalyst: ethylene glycol antimony is added in an amount of 200ppm, a common stabilizer: adding triphenyl phosphate with the addition amount of 20ppm, uniformly mixing the triphenyl phosphate, adding the mixture into a polyester synthesis reaction kettle, carrying out esterification reaction under the protection of nitrogen, wherein the temperature in the kettle is 220-260 ℃, the initial pressure in the kettle is 0.15-0.2MP, and carrying out pressure relief when the esterification rate reaches 96%, so as to complete the esterification reaction; after the esterification reaction is finished, removing excessive diol mixture, and polycondensing for 3.5 hours at 280-290 ℃ under 130Pa environment to obtain the modified copolyester.

Adding polyethylene terephthalate, UV blocking master batch and opening agent master batch in proportion into an extruder I, and carrying out melt extrusion; adding polyethylene terephthalate and modified copolyester in proportion into an extruder II, and carrying out melt extrusion. The melt extruded by extruder I was fed into the A layer in the three layer die of the ABA structure and the melt extruded by extruder II was fed into the B layer in the three layer die of the ABA structure.

The extruder I and the extruder II synchronously extrude and synchronously guide into a T-shaped die head. In the T-shaped die head, the melt of the extruder I is evenly distributed to two sides of the melt of the extruder II, and two groups of melts are laminated and combined according to an A/B/A three-layer structure and flow on a rotating casting sheet cooling drum with the surface temperature of 20 ℃ to obtain laminated casting sheets. Preheating the laminated casting film at 70-85 ℃, rapidly stretching the laminated casting film longitudinally (in the length direction) for 3.5 times by utilizing the difference of the rotation speeds of two rollers under the infrared heating condition, and gradually cooling the laminated casting film at 30-60 ℃ to obtain the longitudinally stretched film. Clamping two sides of a longitudinal drawing film by a clamp, sending the longitudinal drawing film into a transverse drawing box, preheating at 90-115 ℃, continuously and repeatedly stretching the longitudinal drawing film for 3.8 times along the transverse direction (width direction) at 110-130 ℃, carrying out heat treatment and shaping for 7-15s at 240 ℃, cooling at 120 ℃, carrying out traction and winding after UV irradiation with the wavelength of 365nm and the power of 200w for 3 seconds, and obtaining the high-rigidity thin optical polyester film with the thickness of 25 mu m, wherein the thickness of a layer A is 1.5 mu m.

In this example:

the layer A is prepared from the following raw materials: 4 parts by weight of UV blocking master batch capable of blocking a wave band below 350nm, 8 parts by weight of opening agent master batch and 88 parts by weight of polyethylene terephthalate.

The raw materials of the layer B are as follows: 8 parts by weight of modified copolyester and 92 parts by weight of polyethylene terephthalate.

Wherein the content of silica particles in the master batch of the opening agent is 1.0 percent, and the particle size is 2.0 mu m.

Example 9

Preparation of modified copolyester:

according to the mole ratio of the diol mixture to terephthalic acid of 1.28:1, the molar ratio of 2-amyl-9, 10-anthracenediol to ethylene glycol in the diol mixture is 1:9, conventional catalysts: ethylene glycol antimony is added in an amount of 200ppm, a common stabilizer: adding triphenyl phosphate with the addition amount of 20ppm, uniformly mixing the triphenyl phosphate, adding the mixture into a polyester synthesis reaction kettle, carrying out esterification reaction under the protection of nitrogen, wherein the temperature in the kettle is 220-260 ℃, the initial pressure in the kettle is 0.15-0.2MP, and carrying out pressure relief when the esterification rate reaches 96%, so as to complete the esterification reaction; after the esterification reaction is finished, removing excessive diol mixture, and polycondensing for 3.5 hours at 280-290 ℃ under 130Pa environment to obtain the modified copolyester.

Adding polyethylene terephthalate, UV blocking master batch and opening agent master batch in proportion into an extruder I, and carrying out melt extrusion; adding polyethylene terephthalate and modified copolyester in proportion into an extruder II, and carrying out melt extrusion. The melt extruded by extruder I was fed into the A layer in the three layer die of the ABA structure and the melt extruded by extruder II was fed into the B layer in the three layer die of the ABA structure.

The extruder I and the extruder II synchronously extrude and synchronously guide into a T-shaped die head. In the T-shaped die head, the melt of the extruder I is evenly distributed to two sides of the melt of the extruder II, and two groups of melts are laminated and combined according to an A/B/A three-layer structure and flow on a rotating casting sheet cooling drum with the surface temperature of 20 ℃ to obtain laminated casting sheets. Preheating the laminated casting film at 70-85 ℃, rapidly stretching the laminated casting film longitudinally (in the length direction) for 3.5 times by utilizing the difference of the rotation speeds of two rollers under the infrared heating condition, and gradually cooling the laminated casting film at 30-60 ℃ to obtain the longitudinally stretched film. Clamping two sides of a longitudinal drawing film by a clamp, sending the longitudinal drawing film into a transverse drawing box, preheating at 90-115 ℃, continuously and repeatedly stretching the longitudinal drawing film for 3.8 times along the transverse direction (width direction) at 110-130 ℃, carrying out heat treatment and shaping for 7-15s at 240 ℃, cooling at 40 ℃, carrying out traction and winding after UV irradiation with the wavelength of 365nm and the power of 160w for 2 seconds, and obtaining the high-rigidity thin optical polyester film with the thickness of 50 mu m, wherein the thickness of a layer A is 2.0 mu m.

In this example:

the layer A is prepared from the following raw materials: 5 parts by weight of UV blocking master batch capable of blocking a wave band below 350nm, 10 parts by weight of opening agent master batch and 85 parts by weight of polyethylene terephthalate.

The raw materials of the layer B are as follows: 10 parts by weight of modified copolyester and 90 parts by weight of polyethylene terephthalate.

Wherein the content of silica particles in the master batch of the opening agent is 1.0 percent, and the particle size is 2.0 mu m.

Comparative example 1

No modified copolyester was added.

Adding polyethylene terephthalate, UV blocking master batch and opening agent master batch in proportion into an extruder I, and carrying out melt extrusion; polyethylene terephthalate was added in proportion to extruder II and the melt extruded from extruder II was fed into the B layer in the three layer die of ABA structure.

The extruder I and the extruder II synchronously extrude and synchronously guide into a T-shaped die head. In the T-shaped die head, the melt of the extruder I is evenly distributed to two sides of the melt of the extruder II, and two groups of melts are laminated and combined according to an A/B/A three-layer structure and flow on a rotating casting sheet cooling drum with the surface temperature of 20 ℃ to obtain laminated casting sheets. Preheating the laminated casting film at 70-85 ℃, rapidly stretching the laminated casting film longitudinally (in the length direction) for 3.5 times by utilizing the difference of the rotation speeds of two rollers under the infrared heating condition, and gradually cooling the laminated casting film at 30-60 ℃ to obtain the longitudinally stretched film. Clamping two sides of a longitudinal drawing film by a clamp, sending the longitudinal drawing film into a transverse drawing box, preheating at 90-115 ℃, continuously and repeatedly stretching the longitudinal drawing film for 3.8 times along the transverse direction (width direction) at 110-130 ℃, carrying out heat treatment and shaping for 7-15s at 240 ℃, cooling at 60 ℃, carrying out traction and winding after UV irradiation with the wavelength of 365nm and the power of 160w for 4 seconds, and obtaining the high-rigidity thin optical polyester film with the thickness of 38 mu m, wherein the thickness of a layer A is 1.5 mu m.

In this example:

the layer A is prepared from the following raw materials: 3 parts by weight of UV blocking master batch capable of blocking a wave band below 350nm, 8 parts by weight of opening agent master batch and 89 parts by weight of polyethylene terephthalate.

The raw materials of the layer B are as follows: 100 parts by weight of polyethylene terephthalate.

Wherein the content of silica particles in the master batch of the opening agent is 0.3 percent, and the particle size is 2.0 mu m.

Comparative example 2

Preparation of modified copolyester:

according to the mole ratio of the diol mixture to terephthalic acid of 1.3:1, the molar ratio of 1,4 anthracene diol to ethylene glycol in the diol mixture is 4:6, a common catalyst: ethylene glycol antimony is added in an amount of 200ppm, a common stabilizer: adding triphenyl phosphate with the addition amount of 20ppm, uniformly mixing the triphenyl phosphate, adding the mixture into a polyester synthesis reaction kettle, carrying out esterification reaction under the protection of nitrogen, wherein the temperature in the kettle is 220-260 ℃, the initial pressure in the kettle is 0.15-0.2MP, and carrying out pressure relief when the esterification rate reaches 96%, so as to complete the esterification reaction; after the esterification reaction is finished, removing excessive diol mixture, and polycondensing for 3.5 hours at 280-290 ℃ under 130Pa environment to obtain the modified copolyester.

Adding polyethylene terephthalate, UV blocking master batch and opening agent master batch in proportion into an extruder I, and carrying out melt extrusion; adding polyethylene terephthalate and modified copolyester in proportion into an extruder II, and carrying out melt extrusion. The melt extruded by extruder I was fed into the A layer in the three layer die of the ABA structure and the melt extruded by extruder II was fed into the B layer in the three layer die of the ABA structure.

The extruder I and the extruder II synchronously extrude and synchronously guide into a T-shaped die head. In the T-shaped die head, the melt of the extruder I is evenly distributed to two sides of the melt of the extruder II, and two groups of melts are laminated and combined according to an A/B/A three-layer structure and flow on a rotating casting sheet cooling drum with the surface temperature of 20 ℃ to obtain laminated casting sheets. Preheating the laminated casting film at 70-85 ℃, rapidly stretching the laminated casting film longitudinally (in the length direction) for 3.5 times by utilizing the difference of the rotation speeds of two rollers under the infrared heating condition, and gradually cooling the laminated casting film at 30-60 ℃ to obtain the longitudinally stretched film. Clamping two sides of a longitudinal drawing film by a clamp, feeding the longitudinal drawing film into a transverse drawing box, preheating at 90-115 ℃, continuously and repeatedly stretching the longitudinal drawing film for 3.8 times along the transverse direction (width direction) at 110-130 ℃, performing heat treatment and shaping for 7-15s at 240 ℃, cooling at 140 ℃, and performing traction rolling after UV irradiation with the wavelength of 365nm and the power of 250w for 8 seconds to obtain the high-rigidity thin optical polyester film with the thickness of 50 mu m, wherein the thickness of a layer A is 4.0 mu m.

In this example:

the layer A is prepared from the following raw materials: 10 parts by weight of UV blocking master batch capable of blocking a wave band below 300nm, 12 parts by weight of opening agent master batch and 78 parts by weight of polyethylene terephthalate.

The raw materials of the layer B are as follows: 12 parts by weight of modified copolyester and 88 parts by weight of polyethylene terephthalate.

Wherein the content of silica particles in the master batch of the opening agent is 0.3 percent, and the particle size is 3.5 mu m.

Comparative example 3

Preparation of modified copolyester:

according to the molar ratio of the diol mixture to terephthalic acid of 1: the molar ratio of 2-pentyl-9, 10-anthracenediol to ethylene glycol in the diol mixture was 0.5:9.5, usual catalysts: ethylene glycol antimony is added in an amount of 200ppm, a common stabilizer: adding triphenyl phosphate with the addition amount of 20ppm, uniformly mixing the triphenyl phosphate, adding the mixture into a polyester synthesis reaction kettle, carrying out esterification reaction under the protection of nitrogen, wherein the temperature in the kettle is 220-260 ℃, the initial pressure in the kettle is 0.15-0.2MP, and carrying out pressure relief when the esterification rate reaches 96%, so as to complete the esterification reaction; after the esterification reaction is finished, removing excessive diol mixture, and polycondensing for 3.5 hours at 280-290 ℃ under 130Pa environment to obtain the modified copolyester.

Adding polyethylene terephthalate, UV blocking master batch and opening agent master batch in proportion into an extruder I, and carrying out melt extrusion; adding polyethylene terephthalate and modified copolyester in proportion into an extruder II, and carrying out melt extrusion. The melt extruded by extruder I was fed into the A layer in the three layer die of the ABA structure and the melt extruded by extruder II was fed into the B layer in the three layer die of the ABA structure.

The extruder I and the extruder II synchronously extrude and synchronously guide into a T-shaped die head. In the T-shaped die head, the melt of the extruder I is evenly distributed to two sides of the melt of the extruder II, and two groups of melts are laminated and combined according to an A/B/A three-layer structure and flow on a rotating casting sheet cooling drum with the surface temperature of 20 ℃ to obtain laminated casting sheets. Preheating the laminated casting film at 70-85 ℃, rapidly stretching the laminated casting film longitudinally (in the length direction) for 3.5 times by utilizing the difference of the rotation speeds of two rollers under the infrared heating condition, and gradually cooling the laminated casting film at 30-60 ℃ to obtain the longitudinally stretched film. Clamping two sides of a longitudinal drawing film by a clamp, sending the longitudinal drawing film into a transverse drawing box, preheating at 90-115 ℃, continuously and repeatedly stretching the longitudinal drawing film for 3.8 times along the transverse direction (width direction) at 110-130 ℃, carrying out heat treatment and shaping for 7-15s at 240 ℃, cooling at 35 ℃, carrying out traction and winding after UV irradiation with the wavelength of 365nm and the power of 150w for 1 second, and obtaining the high-rigidity thin optical polyester film with the thickness of 6 mu m, wherein the thickness of a layer A is 0.6 mu m.

In this example:

the layer A is prepared from the following raw materials: 0 parts by weight of UV blocking masterbatch, 3 parts by weight of a mouth gag masterbatch, 97 parts by weight of polyethylene terephthalate.

The raw materials of the layer B are as follows: 3 parts by weight of modified copolyester and 97 parts by weight of polyethylene terephthalate.

Wherein the content of silica particles in the master batch of the opening agent is 0.3 percent, and the particle size is 0.8 mu m.

The specific implementation effects are shown in the following table 1.

Table 1 test results table

From the above Table 1, examples 1-9 and comparative examples 1-3, it can be seen that: according to the invention, the modified copolyester is added in the layer B, and the UV blocking master batch and the opening agent master batch in the layer A can effectively improve the integral rigidity of the thin optical polyester film while having good optical performance, and the temperature resistance of the polyester film when reprocessed and heated is obviously improved.

Under the same equipment and process flow, the rigidity of the invention is obviously better than that of the common thin optical polyester film.

Claims (9)

1. The high-rigidity thin optical polyester film is characterized by comprising a layer B and a layer A positioned on two sides of the layer B, wherein the whole is in an ABA superposition structure;

wherein, the preparation raw materials of the layer B comprise: 5-10% by mass of modified copolyester and the balance of pure polyester;

the preparation raw materials of the layer A comprise: 3-5% of UV blocking master batch, 5-10% of opening agent master batch and the balance of pure polyester;

the modified copolyester is prepared from a diol mixture and dibasic acid through esterification and polycondensation reaction; the molar ratio of the diol mixture to the dibasic acid (1.2-1.28) is 1;

The diol mixture consists of an anthracene group-containing diol and ethylene glycol, the molar ratio of the anthracene group-containing diol to the ethylene glycol being (1:9) - (3:7).

2. The thin, highly rigid optical polyester film according to claim 1, wherein the dibasic acid is an aromatic diacid.

3. The thin, highly rigid optical polyester film of claim 1 wherein the anthracene group-containing diol is one of 1,4 anthracene diol, 9-anthracene methanol, or 2-pentyl-9, 10-anthracene diol.

4. The high-rigidity thin optical polyester film according to claim 1, wherein the UV blocking master batch is a UV blocking master batch capable of blocking a wavelength band of 350nm or less and transmitting a wavelength band of 350nm or more.

5. The high-rigidity thin optical polyester film according to claim 1, wherein the opening agent masterbatch is composed of pure polyester and silica particles, the content of the silica particles is 0.3% -1.5% of the weight of the opening agent masterbatch, and the silica particle size is: 1.0-2.0 μm.

6. The high-rigidity thin optical polyester film according to claim 1, wherein the thickness of the polyester film is 6 to 50 μm.

7. The high rigidity thin type optical polyester film according to claim 1, wherein the thickness of the a layer of the polyester film is independently 1 to 2 μm.

8. A method for producing the high-rigidity thin optical polyester film according to any one of claims 1 to 7, comprising the steps of:

step 1: adding pure polyester, UV blocking master batch and opening agent master batch according to the proportioning amount in an extruder I for melt extrusion; adding pure polyester and modified copolyester in the extruder II according to the proportion, and carrying out melt extrusion;

step 2: feeding the melt extruded by the extruder I into an A layer in a three-layer die head of an ABA structure; feeding the melt extruded by the extruder II into a layer B in a three-layer die of an ABA structure; the melt of the layer A and the melt of the layer B flow out together according to the thickness proportion; the high-rigidity thin optical polyester film is obtained through casting, longitudinal drawing, transverse drawing, shaping, cooling, UV irradiation and rolling.

9. The method for producing a high-rigidity thin optical polyester film according to claim 8, wherein the wavelength of the UV irradiation is 365nm, the UV irradiation power is 160-200w, and the UV irradiation time is 2-5 seconds.