CN104513403A - BOPET film with water-based anti-reflection coating coated online and preparation method of BOPET film - Google Patents

Abstract

The invention discloses a BOPET film coated with a water-based anti-reflection coating on-line and a preparation method thereof. The BOPET film comprises a BOPET base layer and a water-based anti-reflection coating adhered to at least one surface of the base layer; the water-based anti-reflection coating The coating contains refractive particles with a diameter of 0.01-10 microns and a refractive index of 1.3-1.45; the water-based anti-reflection coating is coated on-line after the PET slice is stretched longitudinally, and the water-based anti-reflection coating solution is coated Formed on the surface of PET slices; the water-based anti-reflection coating solution contains ≥50wt% water and 100ppm~1000ppm of refractive particles. The total light transmittance of the BOPET film of the invention is more than 94%, which can be improved by about 6% compared with the BOPET film without coating; and the water-based coating solution is environmentally friendly and has no VOC emission. The preparation method of the invention adopts online coating, has simple process and high efficiency, and can be used for mass production.

Description

A kind of BOPET film of online coating water-based anti-reflection coating and preparation method thereof

technical field

The invention relates to the field of surface modification of organic thin film materials, in particular to a BOPET film coated with a water-based anti-reflective coating on-line and a preparation method thereof.

Background technique

Biaxially oriented polyester film, namely BOPET film, is not only widely used in packaging, printing, window film, solar backplane, etc. due to its excellent insulation, dimensional stability, mechanical properties, heat resistance, and gas barrier properties. Products are also used to manufacture optical films such as anti-reflection coatings, prism coatings, diffusion coatings, and hardening coatings.

Optical films not only require the above-mentioned excellent properties of polyester films, but also require polyester films to have high transparency, etc.

The light transmittance of any material can't reach 100%, even the light transmittance of the most transparent optical glass is generally difficult to exceed 95%. The main reasons for the loss of incident luminous flux in the medium are: (1) Reflection of light: reflection is the luminous flux returned by the incident light entering the polymer surface. Reflected luminous flux accounts for most of the light lost as it travels through the media. (2) Absorption of light: The luminous flux of the luminous flux incident on the polymer that is neither transmitted nor reflected is the absorption of light. The amount of light absorption depends on the structure of the polymer itself, mainly referring to the nature of the atomic groups and chemical bonds on the molecular chain. (3) Scattering of light: Scattering of light means that light is incident on the surface of the polymer, and a part of the luminous flux that is neither transmitted nor reflected and absorbed has a relatively small proportion. The reasons for light scattering are: the surface of the product is rough and uneven, the internal structure of the polymer is uneven, such as uneven molecular weight distribution, the coexistence of disordered phase and crystalline phase, etc.

Therefore, in order to obtain a transparent BOPET film, the following conditions need to be met. First, the product is amorphous; second, although it is partially crystallized, the particles are small, smaller than the wavelength range of visible light, and do not interfere with visible light (300~800nm) and near-infrared light in the sunlight spectrum. through.

However, in the stretching process of BOPET film, there is unavoidable thermal crystallization, which causes light to be reflected at the interface between the crystal and the amorphous phase, thereby affecting the transparency, and more or less additives must be added during the preparation of the film. The additive particles can also cause light reflection, and the stretching process will cause gaps between the additive particles and PET molecules, resulting in reflection and affecting transparency.

In order to improve the transparency of the BOPET film, it is common practice to coat the surface of the film with an anti-reflection coating to improve the transparency of the BOPET film. At present, the anti-reflection coating is mainly realized by off-line processing of the BOPET film. Among them, organic coating solutions accounted for the majority.

Contents of the invention

In order to facilitate processing, reduce cost and improve the transparency of the BOPET film, the invention provides a BOPET film coated with a water-based anti-reflective coating on-line and a preparation method thereof.

The solution that the present invention solves its technical problem is: a kind of BOPET film of online coating waterborne anti-reflection coating,

The film comprises a BOPET base layer and a water-based anti-reflection coating adhered to at least one surface of the base layer;

Containing diameter is 0.01～10 micron in the water-based antireflection coating, the refractive particle of refractive index 1.3～1.45;

The water-based anti-reflection coating is formed by coating the water-based anti-reflection coating solution on the surface of the PET slice after the PET slice is stretched longitudinally; the water-based anti-reflection coating solution contains more than or equal to 50wt% water, 100ppm-1000ppm of the refractive particles.

Further, the refractive particles are one or more of magnesium fluoride, spherical silica, calcium carbonate, glass beads, and polymethyl methacrylate.

Further, the thickness of the wet coating formed after online coating of the water-based anti-reflection coating liquid is 0.1-100 microns; preferably 10-60 microns.

Further, the water-based anti-reflection coating solution also contains one or more of polyester, polyethylene, polypropylene, polyvinyl alcohol and polyacrylate, which is used to increase the adhesion between the coating and the base layer. Adhesion, because the solution is water-based, so the polyester, polyethylene, polypropylene, polyvinyl alcohol and polyacrylate are all water-soluble.

Further, the water-based anti-reflection coating solution contains any one or more of dispersants, emulsifiers, and foaming agents to coordinate the above-mentioned polyester, polyethylene, polypropylene, polyvinyl alcohol, and polyacrylic acid Esters, etc., to improve the coating performance of the solution.

Further, the above-mentioned BOPET film coated with a water-based anti-reflection coating online has a total light transmittance ≥ 94%.

The present invention also provides a kind of preparation method of the BOPET film of above-mentioned on-line coating waterborne anti-reflection coating, comprises the following steps:

Extrude and melt PET chips;

After being cooled by a T-shaped die head and a cold drum, it is made into a cast sheet;

Stretch the cast sheet longitudinally;

Through the online coating system, the water-based antireflection coating solution is coated online on the surface of the PET cast sheet after longitudinal stretching;

Transverse stretching and heat setting are carried out.

Further, the on-line coating adopts anilox roll coating, combination coating of anilox roll and rubber roll or die extrusion coating.

Further, the total light transmittance of the obtained BOPET film coated with a water-based anti-reflective coating on-line is ≥94%.

The beneficial effects of the present invention are: the BOPET film with water-based anti-reflection coating of the present invention has a total light transmittance of 94% or higher, and can achieve a total light transmittance of about 6% compared with the BOPET film without coating. Improve; and use water-based coating liquid coating, no VOC emissions, environmentally friendly.

In addition, the preparation method of the present invention adopts on-line coating to form the anti-reflection layer, the process is simple, the obtained coating is thin and uniform, the production speed is high, the efficiency is high, and the cost is low, and it can be used for mass production.

Detailed ways

The invention provides a BOPET film with a total light transmittance ≥ 94% of an online coating of a water-based anti-reflection coating, comprising a BOPET base layer and a water-based anti-reflection coating adhered to at least one surface of the base layer; the water-based anti-reflection coating The coating contains refraction particles; the refraction particles can be inorganic particles or organic particles, as long as they can exist stably on the surface of the BOPET film, the main requirements are that the diameter is 0.1-10 microns and the refractive index is 1.3-1.45; the particle diameter is too small , Difficult to disperse, particle agglomeration leads to uneven effect; when the particle diameter is too large, it is easy to fall from the coating surface. Films with a refractive index greater than 1.45 have insufficient light transmittance. Preferably, the refractive particles are one or more of magnesium fluoride, spherical silica, calcium carbonate, glass beads, and polymethyl methacrylate.

The water-based anti-reflection coating is obtained by stretching the obtained cast sheet longitudinally after the PET chip is extruded and melted, and then coating the water-based anti-reflection coating solution on-line, and then performing transverse stretching and heat setting. When coating, the water-based anti-reflection coating solution contains water greater than or equal to 50wt%, and 100ppm~1000ppm of the refractive particles; when the content of the refractive particles is too small, the anti-reflection effect is not obvious; Increased haze affects appearance. Preferably, the refractive particle content is 300ppm-800ppm.

The used PET chip is a PET chip product that can be used for film production according to those skilled in the art, and does not contain fillers.

In order to improve the adhesion performance of the coating, one or more of polyester, polyethylene, polypropylene, polyvinyl alcohol, polyacrylate, polystyrene and polyurethane can be added to the water-based anti-reflection coating solution. The polymer structure contains water-soluble groups, specifically known water-soluble or water-dispersible ones can be used.

For example, the specific preparation method of the polyester described in the present invention can be any one of the existing known techniques, that is, the acid component or the ester component is used as the raw material, and the alcohol component is sequentially esterified, transesterified, and polycondensed. .

The polyacrylate includes one or more of methyl methacrylate, ethyl methacrylate, n-butyl acrylate, n-butyl methacrylate, and pentyl acrylate. It can be prepared by the known emulsion polymerization method.

Any one or more of dispersants, emulsifiers, and foaming agents may also be included in the water-based anti-reflection coating solution to improve the coating performance of the solution.

The present invention also provides a kind of preparation method of the BOPET film of above-mentioned on-line coating water-based anti-reflection coating, specifically, extrude and melt the PET chips; then make cast sheets after being cooled by T-shaped die head and cold drum; The cast sheet is stretched longitudinally, and then through the online coating system, the water-based antireflection coating solution is coated on the surface of the longitudinally stretched PET cast sheet online; after coating, the transverse stretching and heat setting are carried out.

The online coating method can adopt common online coating process, preferably, anilox roll coating, combination coating of anilox roll and rubber roll or die extrusion coating.

During the online coating process, the water in the water-based anti-reflective coating solution is basically completely evaporated, and the resin and other components are cured, so that the refractive particles are closely adhered to the surface of the film. In this way, an online-coated BOPET film with a water-based anti-reflection coating with a total light transmittance ≥ 94% is obtained.

Example 1

Preparation of water-based antireflection coating solution:

Refractive particles: spherical silica with a diameter of 2 microns and a refractive index of 1.3.

Add appropriate amount of deionized water to the refraction particles to obtain a solution with a refraction particle content of 600ppm; and add 5wt% of polyester resin, 1wt% of polyethylene resin, 2wt% of polypropylene resin, 5wt% of polyvinyl alcohol, 2wt% of n-butyl methacrylate, 1wt% dispersant, 1wt% defoamer, 2wt% emulsifier.

Preparation of BOPET membrane:

Put the dehumidified PET slices into the extruder, melt and extrude; then pass through a T-shaped die head and a cold drum to make a PET cast sheet with a thickness of 2000 μm; Stretch 3.5 times along the machine direction (MD) at a high temperature (i.e. 110°C temperature); use an anilox roller coating method to coat a water-based anti-reflection coating solution on one side of the sheet, and obtain The wet coating thickness is about 28 microns; the sheet is preheated and dried at a temperature higher than the longitudinal stretching temperature, namely 140°C, to further stretch 3.5 times in the transverse direction (TD); The film is heat-treated at a temperature of 235°C in a heat-treatment area of a tenter (5 stage tenter) higher than grade 5; Relaxing 10%; and heat setting the film to produce a 188 μm thick BOPET film coated on both sides with an aqueous anti-reflection coating. The physical properties of the prepared BOPET film are shown in Table 1.

Comparative example 1

At the same time, the same PET chips as in Example 1 were used as raw materials, stretched according to the same stretching process, and the online coating process was removed to obtain an uncoated BOPET film.

Example 2

Preparation of water-based antireflection coating solution:

Refractive particles: polymethyl methacrylate with a diameter of 0.01 micron and a refractive index of 1.4.

Add appropriate amount of deionized water to the refraction particles to obtain a solution with a refraction particle content of 100ppm; and add 4.5wt% polyester resin, 2wt% n-butyl methacrylate, 1.5wt% methyl methacrylate resin, 2wt% Polystyrene, 1wt% polyurethane, 2wt% dispersant, 0.5wt% defoamer, 0.5wt% emulsifier.

Preparation of BOPET membrane:

Put the dehumidified PET slices into the extruder, melt and extrude; then pass through a T-shaped die head and a cold drum to make a PET cast sheet with a thickness of 2000 μm; Stretch 3.5 times along the machine direction (MD) at a high temperature (ie, 110°C); use a combination of anilox roller and rubber roller to coat the front and back sides of the sheet with water-based Through the coating solution, the thickness of the wet coating on each side obtained after coating is 10 microns; the sheet is preheated and dried at a temperature higher than the longitudinal stretching temperature, that is, 140 ° C, to stretch along the transverse direction (transverse direction) (TD)) further stretched 3.5 times; heat treatment at a temperature of 235°C in the heat treatment zone of a 5 stage tenter (5 stage tenter) prepared for the film; in the cooling zone at 200°C Relax the film by 10% in the machine direction and in the transverse direction at or lower temperature; and heat set the film to produce a 125 μm thick BOPET film coated on both sides with an aqueous anti-reflection coating. The physical properties of the prepared BOPET film are shown in Table 1.

Comparative example 2

At the same time, the same PET chips as in Example 1 were used as raw materials, stretched according to the same stretching process, and the online coating process was removed to obtain an uncoated BOPET film.

Example 3

Preparation of water-based antireflection coating solution:

Refractive particles: calcium carbonate with a diameter of 10 microns and a refractive index of 1.45.

The refraction particles were added into an appropriate amount of deionized water to obtain a solution with a refraction particle content of 1000ppm; and adding 0.5wt% polypropylene resin, 2wt% polyvinyl alcohol, 1.5wt% n-butyl methacrylate resin, and 1.0wt% formazan Base methyl acrylate resin, 3wt% polystyrene, 1wt% polyurethane, 0.5wt% dispersant, 0.5wt% defoamer, 0.5wt% emulsifier.

Preparation of BOPET membrane:

Put the dehumidified PET slices into the extruder, melt and extrude; then pass through a T-shaped die head and a cold drum to make a PET cast sheet with a thickness of 2000 μm; Stretch 3.5 times along the machine direction (MD) at a high temperature (i.e. 110°C temperature); use the die extrusion method to coat the water-based anti-reflection coating solution on the front and back sides of the sheet, and coat The thickness of the resulting wet coating on each side is about 60 microns; the sheet is preheated and dried at a temperature higher than the longitudinal stretching temperature, i.e. 140°C, for further stretching in the transverse direction (TD) Stretching 3.5 times; heat treatment at a temperature of 235°C in the heat treatment area of a tenter (5 stage tenter) higher than class 5 prepared for the film; at a temperature of 200°C or lower in the cooling area The film was relaxed 10% in the machine direction and cross direction; and the film was heat set to produce a 250 μm thick BOPET film coated on both sides with an aqueous anti-reflection coating. The physical properties of the prepared BOPET film are shown in Table 1.

Comparative example 3

At the same time, the same PET chips as in Example 1 were used as raw materials, stretched according to the same stretching process, and the online coating process was removed to obtain an uncoated BOPET film.

The physical performance testing method of the PET film obtained in the above-mentioned embodiment and comparative example is as follows:

1) Determination of the total light transmittance of the film: The total light transmittance of the film was measured with a total light transmittance measuring instrument (Nippon Denshoku 300A).

2) Haze test: MH-500 optical projection haze meter is used to test the haze of the film.

Each embodiment implements effect as shown in table 1 |.

Table 1

The preferred embodiments of the present invention have been described in detail above, but the invention is not limited to the described embodiments, and those skilled in the art can also make various equivalent modifications or replacements without violating the spirit of the present invention. These equivalent modifications or replacements are all within the scope defined by the claims of the present application.

Claims (9)

1. a BOPET film for online coating Water antireflection coating, is characterized in that: comprise BOPET stratum basale and stick to the Water antireflection coating at least one surface of BOPET stratum basale;

Containing diameter in described Water antireflection coating is 0.01 ~ 10 micron, and specific refractory power is the refractive power particle of 1.3 ~ 1.45;

Described Water antireflection coating is cut into slices after longitudinal stretching at PET, through being coated with online, formed by Water antireflection coating solution to PET slice surface; Containing the water being more than or equal to 50wt% in described Water antireflection coating fluid, the described refractive power particle of 100ppm ~ 1000ppm.

2. the BOPET film of online coating Water antireflection coating according to claim 1, is characterized in that: described refractive power particle is one or more in magnesium fluoride, preparing spherical SiO 2, calcium carbonate, granulated glass sphere, polymethylmethacrylate.

3. the BOPET film of online coating Water antireflection coating according to claim 1, is characterized in that: the wet coating thickness that described Water antireflection coating fluid is coated with rear formation is online 0.1 ~ 100 micron.

4. the BOPET film of online coating Water antireflection coating according to claim 1, is characterized in that: also containing one or more in interpolation vibrin, polyvinyl resin, acrylic resin, polyvinyl alcohol resin and polyacrylate resin in described Water antireflection coating fluid.

5. the BOPET film of online coating Water antireflection coating according to claim 4, is characterized in that: comprise in described Water antireflection coating fluid in dispersion agent, emulsifying agent, pore forming material any one or more than one.

6. the BOPET film of the online coating Water antireflection coating according to any one of claim 1-5, its total light transmittance >=94%.

7. a preparation method for the BOPET film of the online coating Water antireflection coating as described in any one of claim 1-5, is characterized in that, comprise the following steps:

Melting is extruded in PET section;

By making slab after T-shaped die head, cold drum cooling;

Slab is carried out longitudinal stretching;

By online coating, the PET slab surface coated Water antireflection coating fluid after longitudinal stretching;

Carry out cross directional stretch and heat setting type.

8. preparation method according to claim 7, is characterized in that: described online coating be adopt anilox roll coating, anilox roll and rubber roll combine be coated with or die head extrusion coated.

9. preparation method according to claim 7, is characterized in that: the BOPET film of the online coating Water antireflection coating obtained, its total light transmittance >=94%.