KR20210114609A - High transparent polyester film - Google Patents

Abstract

The present invention relates to a high transparent polyester film having a three-layered structure, in which at least one of skin layers comprises alumina fine particles having α-crystalline phases and silicon dioxide particles, and in particular, to a high transparent polyester film for windows.

Description

High transparent polyester film {High transparent polyester film}

The present invention relates to a high-transparency polyester film for windows that is excellent in high transparency, particle visibility, and post-color processing.

The polyester film for windows is required to be excellent in high transparency, particle visibility, winding property, and post-coloring processability.

In general, a polyester film forms fine irregularities on the surface of the film by adding an inert inorganic filler to improve slip properties. Specifically, a method of producing a film by mixing inorganic particles such as kaolin, calcium carbonate, silica, titanium dioxide, barium sulfate, etc. into a master batch and mixing with a polyester resin is common.

When the amount of these inorganic fillers increases, the slip property is improved by increasing the number of fine irregularities on the film surface, but there is a problem in that the transparency of the film is reduced. A method of increasing the transparency of the film by coating (inline coating) with a material imparting slip properties to one or both surfaces of the film is used.

In the coloring process of polyester film for windows, there are dye coating method and dye dyeing method. The general dye coating method is simple and inexpensive, but there is a problem in that long-term dyeing quality such as discoloration by sunlight deteriorates. In order to secure it, a dye-dye method of dyeing the base film is widely used.

In the case of a window film that requires high-quality dyeing quality, a non-coated product is generally required to facilitate dyeing of dyes and secure appearance quality. However, in the uncoated polyester film, there is a problem in that it is difficult to secure high transparency and slip property at the same time by adjusting the input amount of the existing inorganic filler.

The present invention has been devised to solve the above problems, and an object of the present invention is to provide a polyester film for windows excellent in both slip properties and transparency.

As a means for solving the above-mentioned problems,

The highly transparent polyester film of the present invention is a three-layer polyester film including two skin layers and one core layer, wherein at least one of the skin layers includes alumina particles having an α-crystalline phase and silicon dioxide particles characterized in that

In addition, the particle diameter of the alumina fine particles is characterized in that D (50) is 200 ~ 500nm.

In addition, the alumina fine particles are characterized in that the Mohs hardness is 8 or more.

In addition, the content of the alumina fine particles is characterized in that 450 ~ 1000ppm compared to the polyester resin of the skin layer.

In addition, the particle diameter of the silicon dioxide particles is characterized in that D(50) is 1.0 ~ 1.5㎛ and D(99) is 3.0 ~ 3.5㎛.

In addition, the pore volume of the silicon dioxide particles is characterized in that less than 1.3 ㎖ / g.

In addition, the diameter of the pores is characterized in that 15nm or less.

In addition, the content of the silicon dioxide particles is characterized in that 50 ~ 100 ppm compared to the polyester resin of the skin layer.

In addition, the silicon dioxide particles are characterized in that the Mohs' hardness is 6 or more.

In addition, the polyester film is characterized in that the haze is 1.2% or less, the friction coefficient is 0.33 or less, the MD strength value is 21Kgf/mm ² or more, the particle visibility Lv.3 or less, and the maximum surface roughness Rmax is 0.6 μm or more.

The highly transparent polyester film of the present invention has excellent slip and high transparency due to the addition of fine particles with high hardness and excellent particle visibility, and has good winding processability by mixing silicon dioxide as a spike filler, and does not require a separate coating process. An ester film can be provided.

1 is a schematic diagram showing the cross-sectional structure of a polyester film having a three-layer structure of the present invention;
Figure 2 is a surface SEM Image according to the pore size of silica particles.

Hereinafter, the highly transparent polyester film of this invention is demonstrated in more detail.

The present invention is a three-layer polyester film comprising two skin layers and one core layer, wherein at least one of the skin layers comprises alumina particles having an α-crystalline phase and silicon dioxide particles. It relates to a highly transparent polyester film for windows.

The polyester film has a three-layer structure, and has a structure in which a skin layer (A) - a core layer (B) - a skin layer (A) are laminated as shown in FIG. 1 .

The polyester film includes two skin layers (A), and at least one of the two skin layers includes alumina fine particles.

The alumina fine particles are preferably in an α-crystalline phase.

The particle diameter of the alumina fine particles has a D(50) of 200 to 500 nm. Reducing the scattering by inorganic particles in the film can minimize the scattering of visible light, and the degree of scattering is a function of the difference in refractive index between the particles and the substrate and the particle size. It can be seen that it is an important variable that makes the degree of scattering small. The Rayleigh scattering equation is as follows, and Rayleigh scattering occurs when the scattering coefficient α, which has the most influence on the scattering S, is less than 0.4.

S=((m ² -1)/(m ² +1)) ² *(4λ ² α ⁶ /3π)

(S = scattering, m = np/nb, np = refractive index of particles, nb = refractive index of substrate, scattering coefficient α = πD/λ, D = particle size, λ = wavelength)

Therefore, for example, the theoretical minimum particle diameter for transparency at 400 nm visible light wavelength is 50 nm, and in order to reduce interference with the maximum visible light wavelength, it should be smaller than 380 nm to increase transparency. At this time, when the central particle D (50) is less than 200 nm, slip property is deteriorated, there is a problem of scratch generation, and when it exceeds 500 nm, there is a problem in that the optical properties are lowered.

It is preferable that the said alumina microparticles|fine-particles have Mohs' Hardness 8 or more. If the Mohs hardness is less than 8, scratches may occur in the process of running with the roll during film running.

The content of the alumina particles is preferably 450 to 1000 ppm compared to the polyester resin included in each skin layer (A). The refractive index of the alumina particles is 1.78, and due to the difference in refractive index with polyester resin, optical properties may deteriorate due to scattering when excessively added. And, if it exceeds 1000ppm, there is a problem in that the optical properties are deteriorated.

At least one of the two skin layers in the present invention comprises silicon dioxide.

The particle diameter of the silicon dioxide D (50) is 1.0 ~ 1.5㎛. If it is less than 1.0㎛, protrusions and wrinkles may occur due to the residual air layer in the film winding process, and thus the winding appearance quality may be deteriorated. may be lowered. Also, D(99) is 3.0 to 3.5 μm. When the thickness is less than 3.0 μm, the film surface roughness is lowered and blocking between the back surfaces of the film may occur, and when it is more than 3.5 μm, particle visibility and optical properties may be deteriorated.

Preferably, the pore volume of the silicon dioxide particles is 1.3 ml/g or less. When it exceeds 1.3ml/g, the specific surface area of the particles is reduced and the charge density due to the silanol groups on the surface of the particles is low, which causes agglomeration between particles around the silica, thereby reducing the optical properties of the film and increasing the viscosity when manufacturing the polymerization master chip. There arises a problem that the dispersibility of the particles is lowered.

The diameter of the pores of the silicon dioxide particles is preferably 15 nm or less. If it exceeds 15 nm, the size of the primary silica particles is large, the internal density is low, and the bonding strength is low, so the surface roughness due to particle crushing during grinding is low, the slip property is lowered, and the number of particles per unit volume is increased, resulting in a decrease in optical properties. do.

The content of the silicon dioxide particles is preferably 50 to 100 ppm compared to the polyester resin of the skin layer (A). If it is less than 50ppm, the surface slip property of the film is lowered and the friction properties are high, so winding and running properties are deteriorated.

In the present invention, at least one of the two skin layers preferably contains alumina fine particles and silicon dioxide at the same time. By including alumina fine particles and silicon dioxide at the same time, it is possible to prepare a polyester film having excellent slip properties and high transparency, good winding processability, and no need for a separate coating.

Hereinafter, the present invention will be described in detail through specific examples and comparative examples, and these examples are only for illustrating the present invention and should not be construed as limiting the scope of the present invention.

The measuring method for the properties of the polyester film shown in Examples and Comparative Examples to be described later is as follows.

(One) optical properties

Film specimens were measured using a Haze Meter (model name: Nipon denshoku, Model NDH 5000).

(2) coefficient of friction

The surface of the film specimen was measured using a friction coefficient measuring instrument (model name: FP-2250) manufactured by Thwing-Albert Instrument Company.

(3) surface roughness

To measure the roughness of the film surface, it was measured using a surface roughness meter (model name: Kosaka Laboratory ET 4000A).

(4) Particle visibility

Particle visibility: Lv.1 (weak particle vision) ~ Lv.5 (strong particle vision)

Particle visibility Lv. Using the film for each type as a reference, the visibility of the particles was evaluated with the naked eye using a fluorescent lamp on the film surface.

Example One

의 온도 범위에서 3.3배 연신하고, 215 ~ 235

의 온도 범위에서 열처리를 하여 평균 두께 23㎛인 3-layer(A-B-A 구조)의 이축 연신 폴리에스테르 필름을 제조하였다.Polyethylene mixed in a master batch with alumina particles having an average particle size (D(50)) of 300 nm and silicon dioxide having an average particle size of 1.5 μm, a pore volume of 1.2 ml/g, and a pore diameter of 14 nm as shown in Table 1 below. Terephthalate (raw material A) and polyethylene terephthalate (raw material B) having an intrinsic viscosity of 0.62 dl/g containing no particles were extruded through an extrusion die and cooled in a casting drum to prepare a sheet. The sheet thus produced is stretched 3.0 times in the longitudinal direction at a temperature range of 75 to 135° C., and then 90 to 145 in the transverse direction.

Stretched 3.3 times in the temperature range of 215 ~ 235

A 3-layer (ABA structure) biaxially oriented polyester film having an average thickness of 23 μm was prepared by heat treatment in a temperature range of .

Example 2

Polyethylene terephthalate (raw material A) by mixing alumina particles with an average particle size of 500 nm and silicon dioxide with an average particle size of 1.5 μm, a pore volume of 1.2 ml/g, and a pore diameter of 14 nm in the master batch at the ratio shown in Table 1 below. A 3-layer polyester film was prepared in the same manner as in Example 1, except that

Example 3

Polyethylene terephthalate (raw material A) by mixing alumina particles with an average particle size of 300 nm and silicon dioxide with an average particle size of 1.5 μm, a pore volume of 1.2 ml/g, and a pore diameter of 14 nm in the master batch at the ratio shown in Table 1 below. A 3-layer polyester film was prepared in the same manner as in Example 1, except that

comparative example One

Polyethylene terephthalate (raw material A) in which alumina particles having an average particle size of 300 nm and silicon dioxide having an average particle size of 1.5 μm, a pore volume of 1.2 ml/g, and a pore diameter of 14 nm were mixed in the master batch at the ratios shown in Table 1 below. A polyester film was prepared in the same manner as in Example 1, except that the film was prepared as a 1-Layer.

comparative example 2

Polyethylene terephthalate (raw material A) by mixing alumina particles with an average particle size of 300 nm and silicon dioxide with an average particle size of 1.5 μm, a pore volume of 1.6 ml/g, and a pore diameter of 21 nm in the master batch at the ratio shown in Table 1 below. A 3-layer polyester film was prepared in the same manner as in Example 1, except that

comparative example 3

A 3-layer polyester film was prepared in the same manner as in Example 1, except that polyethylene terephthalate (raw material A) was prepared using alumina particles having an average particle size of 300 nm alone in the ratio shown in Table 1.

comparative example 4

Except that polyethylene terephthalate (raw material A) was prepared by using silicon dioxide with an average particle size of 1.5 μm, pore volume of 1.2 ml/g, and pore diameter of 14 nm alone at the ratio of Table 1, Similarly, a 3-layer polyester film was prepared.

comparative example 5

A 3-layer polyester film was prepared in the same manner as in Example 1, except that polyethylene terephthalate (raw material A) was prepared using barium sulfate having an average particle size of 1.4 μm alone in the ratio shown in Table 1.

The structure and thickness of the polyester films of Examples and Comparative Examples and the mixing ratio of inorganic particles are shown in Table 1 below.

The optical properties, friction coefficient, surface roughness, and particle visibility of the polyester films obtained in Examples and Comparative Examples are shown in Table 2 below.

The polyester film of the present invention has a haze of 1.2% or less, a friction coefficient of 0.33 or less, an MD strength value of 21Kgf/mm ² or more, particle visibility Lv.3 or less, and a maximum surface roughness Rmax of 0.6 µm or more.

A: skin layer
B: core layer

Claims (9)

A three-layer polyester film comprising two skin layers and one core layer, wherein at least one of the skin layers comprises alumina particles having an α-crystalline phase and silicon dioxide particles. polyester film. [2] The highly transparent polyester film according to claim 1, wherein the particle diameter of the alumina particles has a D (50) of 200 to 500 nm. The highly transparent polyester film according to claim 1, wherein the alumina particles have a Mohs hardness of 8 or more. The highly transparent polyester film according to claim 1, wherein the content of the alumina fine particles is 450 to 1000 ppm compared to the polyester resin of the skin layer. The highly transparent polyester film according to claim 1, wherein the silicon dioxide particles have a particle diameter of D (50) of 1.0 to 1.5 μm and D (99) of 3.0 to 3.5 μm. The highly transparent polyester film according to claim 1, wherein the pore volume of the silicon dioxide particles is 1.3 ml/g or less. The highly transparent polyester film according to claim 6, wherein the pores have a diameter of 15 nm or less. The highly transparent polyester film according to claim 1, wherein the content of the silicon dioxide particles is 50 to 100 ppm compared to the polyester resin of the skin layer. The polyester film according to any one of claims 1 to 8, wherein the polyester film has a haze of 1.2% or less, a friction coefficient of 0.33 or less, an MD strength value of 21Kgf/mm ² or more, a particle visibility Lv.3 or less, and a maximum surface roughness Rmax of 0.6 High transparent polyester film, characterized in that not less than ㎛.

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