KR20040097743A - Biaxially stretched polyester film - Google Patents

Abstract

PURPOSE: Provided is a biaxially oriented multilayered white polyester film which has a low specific gravity, excellent touch, whiteness and light screening property and a good apparent tone. CONSTITUTION: The biaxially oriented polyester film comprises a porous polyester resin layer (B layer) containing an insoluble thermoplastic resin; a gloss layer (A layer) which comprises a polyester resin having an 60 degree gloss of 100 % or more and is layered on the one face of the B layer; and a matt layer (C layer) which comprises a polyester resin having an 60 degree gloss of 50 % or less and is layered on the other face of the B layer, and has a density of 0.55-1.25 g/cm3. At least one face of the polyester film is coated with a coating solution simultaneously. Preferably the coating solution-coated layer has an antistatic property, a releasing property or an easy adhesion.

Description

Biaxially stretched polyester film

The present invention relates to a biaxially-stretched laminated polyester film, and more particularly, to give a new function of forming fine pores on the surface of the film by particle design technology to have excellent properties as an opaque synthetic paper for printing, imaging, advertising, exhibition It relates to a biaxially stretched polyester film that can be applied to a wide range of industrial applications.

Polyethylene terephthalate is widely used as a polymer processed product because of its excellent physical and chemical properties. Especially, porous polyester film is actively developed as a substitute for labels, cards, white plates, photo papers, and image papers. ought. Synthetic paper containing synthetic resin as the main raw material has excellent water resistance, hygroscopicity, dimensional stability, surface smoothness, printability, glossiness, sharpness and mechanical strength. Conventionally, as a white film for synthetic paper, an olefin resin is used as a main raw material, a small amount of additives and an inorganic filler are added thereto, and a polyolefin-based film or polyester resin in which a plurality of fine bubbles are provided inside the film by biaxial stretching. A white laminated polyester film having a plurality of fine pores in the film has been used by filling a matrix with a thermoplastic resin which is incompatible with polyester in a matrix.

A method for producing a film having fine pores inside the film by filling an appropriate amount of thermoplastic resin incompatible with the polyester resin in a matrix is already known. Examples of the thermoplastic resin used at this time include polyolefins and polystyrenes.

As an example, GB 1195153 proposes a method for producing a film having a plurality of fine pores by filling a polyamide or polypropylene resin with an appropriate amount of polyester resin and stretching it. In addition, US Pat. No. 35,79,609 discloses polyethylene terephthalate as a main raw material and 40% by weight of polymer materials such as polyolefin polymers such as polyethylene, polypropylene, polybutylene, polymethylpentene, ethylene vinyl acetate copolymer, and polytetra methylene oxite. The production method of the biaxially oriented film which has many micropores by adding below is introduced. US Pat. No. 3,640,944 also discloses a method for producing a biaxially stretched porous film by adding 1 to 30% by weight of a polymer material such as polysulfone and polymethylpentene and 0.2 to 3% by weight of a photowetting agent to polyethylene terephthalate. have. In addition, British Patent GBP 1563591 adds an incompatible thermoplastic resin to a polyester resin, and adds a bubble accelerator such as barium sulfate and polyolefin having an average particle diameter of 0.5 to 10 µm to produce a porous polyester. This is introduced.

However, the white porous polyester film having excellent flexibility obtained by adding an incompatible polymer to a polyester such as polypropylene or polystyrene to a conventional polyester resin and adding fine particles such as titanium oxide or barium sulfate thereto has an uneven distribution of pores. In addition, the handling properties and sensitivity of the film is inferior, and printability and reproducibility of whiteness are inferior.

In particular, in recent years, the inkjet printing method has been rapidly applied to facsimile machines, printers, and plotter devices because of its low noise, high speed recording, easy full colorization, and low cost. On the other hand, as the recording speeds up and the full color progresses, high quality characteristics are also required for the recording sheets.

For example, in order to increase the sharpness of a printed image, a demand for color (b value) and surface gloss of a recording sheet is urgently required even when using synthetic paper or plastic film as a recording sheet.

The present invention is to provide a high-functional white film that can be used for printing, imaging, advertising, exhibition, etc. In general, in the graphic applications, the surface properties of the white film is emerging as an important requirement, especially the color of the film surface and The glossiness makes a lot of difference in product preference and quality. In addition, the glossiness of the product appears to vary greatly depending on the physical properties of the film or the surface design of the substrate, the surface properties are changed by artificially controlling the surface roughness of the substrate. The glossiness of the substrate affects post-processing such as printing, and also has a great influence on the quality of the product.

The object of the present invention is that in a conventional white film, a film obtained by adding a large amount of fine particles of titanium oxide has good whiteness or light blocking property, but its apparent color tone (b value) is too low so that a high quality color-water image such as a video printer or photo paper In the case of use as a base material, the color tone of the film is not bright and the color tone of the color-transfer image is unclear, and since titanium oxide is strongly active, yellowness is easily yellowed by light.

The present invention solves these problems, has excellent color tone (b value) and flexibility, good whiteness and light shielding properties, and can be applied to a multilayer polyester film that can be applied to various product applications such as materials of electric and electronic products in the future. The purpose is to provide.

In order to achieve the above object, in the present invention, the polyester resin layer contains a thermoplastic resin which is incompatible with the porous polyester resin layer (B layer), and the surface 60 degrees glossiness is 100% on one side of the resin layer (B layer). The laminated glaze layer (A layer) mainly containing the above polyester resin is laminated | stacked, and the other surface of the said porous polyester resin layer (B layer) has a polyester resin whose surface 60 degree glossiness is 50% or less as a main body. Form a porous polyester film having a three-layer structure laminated a matte layer (C layer), wherein the polyester resin layer (B layer) contains inorganic particles having an average particle diameter of 0.05 ~ 5.0㎛ and a small amount of fluorescent brightener , The gloss layer (A layer) and the matte layer (C layer) each contain silica particles of different particle diameters, and at least one surface of the gloss layer (A layer) and the matt layer (C layer) In order to give acrylic type, polyester type, pole After coating water-soluble coating liquids such as urethane-based and water-soluble coating liquids of silicone, respectively, coextrusion, compounding and stretching using a biaxial stretching mechanism, the apparent density of the film is 0.55g / cm3 or more, 1.25 g / cm3 or less To obtain the laminated polyester film of the present invention.

In the present invention, as the thermoplastic resin incompatible with the polyester resin, a porous polyester resin layer (B) using a polyolefin resin or a polystyrene resin having a melt index of 2 to 20 g / min is used. Layer) to contain inorganic particles having a particle size of 0.05 to 5.0 μm in average particle size and some fluorescent brighteners. The content of inorganic particles is preferably 5 to 30% by weight, and the content of fluorescent brighteners is 0.005 to 0.5. Weight percent is preferred.

In addition, the matte layer (C layer) contains 0.5 to 10 wt% of silica particles having an average particle diameter of 1 to 20 μm, and the gloss layer (A layer) is 0.5 wt% of silica particles having an average particle diameter of 0.5 to 5 μm. It should be contained in the range not exceeding.

The production of the laminated white polyester film of the present invention is based on a single layer white polyester film processing technology, and co-extrusion technology is incorporated therein, and the white film manufacturing technology is a high-level process in addition to the general polyester film manufacturing technology. Technology is required. In particular, in recent years, since a wide range of polyester production lines have become common, development of process technology must be preceded in order to manufacture a white polyester film filled with a large amount of inorganic particles.

As the inorganic particles added to the porous polyester resin layer (B layer) in the present invention, one or more selected from titanium dioxide, calcium carbonate, silica, kaolin, mica, talc, and barium sulfate is used. At this time, when titanium dioxide is used as the inorganic particles, since titanium dioxide filled in a large amount lowers the intrinsic viscosity of the matrix, the intrinsic viscosity of the polyester matrix must be maintained at an appropriate level. If the viscosity is too low, there is a high possibility that breakage occurs in film production. Therefore, a large amount of inorganic particles act as a nucleating agent of the polymer melt during the casting process is required crystallization control technology. In addition, these particles limit the stretchability of the matrix, and thus require a stretching mechanism different from that of a conventional polyester film. Therefore, the average particle diameter of the inorganic particles to be added is preferably 0.05 to 5 µm, more preferably 0.1 to 0.5 µm. When the average particle size of the particles is less than 0.05 μm, the particles aggregate to reduce particle dispersibility in the film. When the size of the particles is 5 μm or more on average, the interaction force between the particles and the particles and the matrix is weak, and thus the stretching process is performed. There is a lot of air bubbles, which can cause process instability.

On the other hand, the filling amount of the inorganic particles is preferably 5 to 30% by weight, more preferably 10 to 20% by weight. When the filling amount is 5% by weight or less, the whiteness is lowered and the silver penetrating force does not reach an appropriate required value. When the filling amount exceeds 30% by weight, the flow characteristics of the polymer change (for example, a decrease in the swelling phenomenon of the melt and a melt Increased sagging phenomenon) Difficulty in film forming process due to lowered stretchability. In addition, the optically used brightener is a bisbenzazole-based brightener, particularly 2, 2 '-(1,2-ethenediyldi-4,1-phenylene) bisbenxazole is suitable, and the amount of addition is 0.005-0.5 weight% is preferable, More preferably, 0.05-0.2 weight% is good. When the addition amount is less than 0.005% by weight, the whitening effect is insignificant. When the addition amount is more than 0.5% by weight, the whiteness decreases due to excessive reflectance.

In the present invention, it is possible to obtain the required glossiness by inputting the roughness of the film surface using coextrusion technology and inorganic particle design technology in order to control the surface properties of the film. As the silica particles used in the gloss layer (A layer) and the matt layer (C layer) of the present invention, those having different particle sizes are used. It is preferable that the average particle diameter of the silica particle used for a glossy layer (A layer) is 0.5-5 micrometers, and the addition amount does not exceed 0.5 weight%. In addition, the silica particle used for a matte layer (C layer) has an average particle diameter of 1-20 micrometers, and the addition amount shall be in the range of 0.5-10 weight%. Moreover, it is preferable to make thickness of a glossiness layer (A layer) and a matte layer (C layer) into 1-10 micrometers. When the size of the silica particles used for the glossy layer (A layer) and the matte layer (C layer) is 0.5 μm and less than 1 μm, respectively, it is difficult to obtain sufficient matting and printability, and the average particle size is 5 μm or 20 μm. When exceeding each, breakage occurs frequently during film production.

It is important that the laminated polyester film of the present invention has an apparent density of 0.55 g / cm 3 or more and 1.25 g / cm 3 or less. When the apparent density of the laminated polyester film is 1.25 g / cm 3 or more, it is not preferable because the captionability and flexibility of the film are not imparted. In addition, when the apparent density becomes 0.55 g / cm 3 or less, there is a closed end in which the amount of internal microbubbles increases and the strength of the film decreases. In the present invention, at least one of the gloss layer (A layer) and the matte layer (C layer) is coated with a water-soluble coating liquid outward to impart easy adhesiveness and mold release property, but in order to impart easy adhesiveness, acrylic or polyester A water-soluble coating liquid having a main component or a polyurethane type as a main component is used, and a water-soluble coating liquid having a silicone type as a main component is used to impart releasability. In addition, the glossiness, which is one of the main physical properties of the laminated polyester film of the present invention, is optically determined in evaluating the appearance of the film surface, and depends on the reflectivity of the surface and linear light. Since the glossiness is sensed by the human eye, it is necessary to define the visually observed characteristic difference as an objective value through the device analysis. That is, the intensity of the reflected light with respect to the intensity of the incident light is measured and determined as a specific angle. More specifically, it is determined as a function of the refractive index of the surface, the angle of incident light, and the surface roughness. If the reflecting surface is flat, the reflection intensity can be predicted by Fresnel's equation at a given incident light angle. For example, when the refractive index is constant, when the incident angle increases, the intensity of the reflected light with respect to the intensity of the incident light increases. In general, when measuring glossiness, a flat plate having a known refractive index is used to compare its gloss value with that of the material to be measured. Therefore, glossiness is expressed as a ratio of the intensity of the reflected light to the intensity of the incident light of the material to be measured with respect to the reference value.

The film has a difference in glossiness between the stretching direction and the orthogonal direction in the stretching direction due to the difference in the stretching mechanism, and this difference decreases as the amount of added particles increases. This is because the higher the amount of particles, the less the difference in refractive index because it controls the degree of stretching, and the higher the amount of particles, the larger the amount of particles, the greater the effect of the matting effect of particles and voids in the matrix than the matting effect of surface roughness It is estimated that the difference in glossiness due to the difference in roughness of the excessive back surface is canceled by that much. Therefore, the change in glossiness with thickness at the same particle content tends to decrease slightly because the thickness is increased, the light scattering ability by the particles in the polymer matrix is increased.

60 degree glossiness, which is the main physical property of the present invention, was measured by the method of ASTM D 523, and the apparent density was measured by the method of ASTM D 1505. Adhesion is measured by ASTM D 3359 method, and the adhesion evaluation for ink adopts the evaluation criteria of cross-cut tape test among the X-cut tape test and cross-cut tape test of ASTM D 3359, using 5B, 4B, 3B. 6B, 2B, 1B, 0B.

5B: The edge of the cut part is completely smooth and the grid is not square.

4B: A small piece of coating falls at the intersection of the lattice and the affected area is less than 5%.

3B: Small pieces fall off at the intersection of the edge and cut, affected

The area is 5% to 15% of the grid.

2B: Some of the applied edges and squares fall into pieces and the area affected is between 15% and 35% of the grid.

1B: The coating is peeled off in the form of a large strip along the edge of the cut, all squares fall off, and the affected area is 35% to 65% of the grid.

* 0B: When peeled off and separated, it is worse than Grade 1B, and the affected area is 65% or more.

Below. The present invention will be described in detail by way of examples.

Example 1

Polyethylene terephthalate with an intrinsic viscosity of 0.65 dl / g containing no particles was used as the raw material PM1, and polypropylene having a melt index of 10 g / min containing no particles was used as the raw material PM2, and titanium dioxide having an average particle size of 0.3Φ µm 50 Polyethylene terephthalate containing 0.1% by weight and fluorescent brightener (OB-1) was used as raw material PM3, and polyethylene terephthalate containing 5% by weight of silicon dioxide having an average particle size of 4 탆 was used as raw material PM4. Polyethylene terephthalate containing 1 wt% of silicon dioxide having a particle size of 2 탆 is used as the raw material PM5. The raw materials PM1, PM2, PM3, PM4, PM5 were dried in weight percent at the weight percent ratio shown in [Table 1], then laminated in three layers in the feed block, extruded through a coextrusion die and cooled in a casting drum. To prepare a sheet. The sheet was stretched 3.0 times in the longitudinal direction at a temperature in the range of 75 to 130 ° C., and then coated on both sides with an inline coater containing a water dispersion containing 2.0% by weight of a water-soluble acrylic emulsion. Stretching 3.3 times in the transverse direction in the temperature range was heat-treated at 215 ~ 235 ℃ to produce a film having an average thickness of 50㎛.

Each layer thickness of the produced laminated film was 3㎛ / 44㎛ / 3㎛.

TABLE 1

division Floor type Layer thickness (Μm) Content (weight%) Remarks PM1 PM2 PM3 PM4 PM5 Example 1 A 3 90 0 0 0 10 Lamination B 44 75 10 15 0 0 C 3 55 0 0 45 0 Example 2 A 5 90 0 0 0 10 Lamination B 40 75 10 15 0 0 C 5 55 0 0 45 0 Example 3 A 3 90 0 0 0 10 Lamination B 44 75 10 15 0 0 C 3 35 0 0 65 0 Example 4 A 5 90 0 0 0 10 Lamination B 40 75 10 15 0 0 C 5 35 0 0 65 0 Comparative Example 1 - 50 60 0 30 0 10 fault Comparative Example 2 - 50 60 0 30 10 0 fault

Example 2

A film having an average thickness of 50 μm was prepared in the same manner as in [Table 1] and Example 1. The thickness of each layer of the produced laminated film was 5 µm / 40 µm / 5 µm.

Example 3

A film having an average thickness of 50 μm was prepared in the same manner as in [Table 1] and Example 1.

The thickness of each layer of the produced laminated film was 3 µm / 44 µm / 3 µm.

Example 4

A film having an average thickness of 50 μm was prepared in the same manner as in [Table 1] and Example 1.

The thickness of each layer of the produced laminated film was 5 µm / 40 µm / 5 µm.

Comparative Example 1

Polyethylene terephthalate with an intrinsic viscosity of 0.65 dl / g without particles as raw material PM1, polypropylene with 10 g / min of melt index without particles as raw material PM2, and titanium dioxide 50 with an average particle size of 0.3 탆 Polyethylene terephthalate containing 0.1% by weight and fluorescent brightener (OB-1) was used as the raw material PM3, and polyethylene terephthalate containing 5% by weight of silicon dioxide having an average particle size of 4 탆 was used as the raw material PM4. Polyethylene terephthalate containing 1 wt% of silicon dioxide having a particle size of 2 탆 was used as the raw material PM5. The raw materials PM1, PM2, PM3, PM4 and PM5 were dried in weight percent at the weight percent ratio shown in Table 1, and then extruded into a single layer to cool in a casting drum to obtain a sheet. The sheet was stretched 3.0 times in the longitudinal direction at a temperature in the range of 75 to 130 ° C., then stretched 3.3 times in the transverse direction at a temperature in the range of 90 to 145 ° C., and heat-treated in the temperature range of 215 to 235 ° C. to average thickness. A 50 μm film was obtained.

Comparative Example 2

In the same manner as in Table 1 and Comparative Example 1, a film having an average thickness of 50 μm was prepared. The particle type, particle amount, additive content, glossiness and density of Examples and Comparative Examples are shown in Table 2 below, and the adhesion to ink is shown in Table 3 below.

TABLE 2

division layer Layer thickness (㎛) Titanium dioxide content (% by weight) 4 μm silica content (% by weight) 2 μm silica content (% by weight) Polypropylene content (% by weight) Glossiness (%) Density (g / cm 3) Example 1 Coating layer 0.05 - - - - 132 0.96 A 3 0 0 0.1 0 - B 43.9 5 0 0 15 - C 3 0 2.25 0 0 - Coating layer 0.05 - - - - 38 Example 2 Coating layer 0.05 - - - - 127 1.01 A 5 0 0 0.1 0 - B 39.9 5 0 0 15 - C 5 0 2.25 0 0 - Coating layer 0.05 - - - - 27 Example 3 Coating layer 0.05 - - - - 134 0.98 A 3 0 0 0.1 0 - B 43.9 5 0 0 15 - C 3 0 3.25 0 0 - Coating layer 0.05 - - - - 22 Example 4 Coating layer 0.05 - - - - 136 1.06 A 5 0 0 0.1 0 - B 39.9 5 0 0 15 - C 5 0 3.25 0 0 - Coating layer 0.05 - - - - 18 Comparative Example 1 - - 15 0 0.1 0 72 1.45 Comparative Example 2 - - 15 0.5 0 0 42 1.45

TABLE 3

division layer Adhesive to Ink bookbinder solvent bookbinder solvent bookbinder solvent bookbinder solvent bookbinder solvent AC EA NC TOL / MEK EVA TOL / IPA / EA VC-VA MEK CAB MEK Example 1 Coating layer 4B 4B 5B 4B 5B A - - - - - B - - - - - C - - - - - Coating layer 4B 4B 5B 4B 5B Example 2 Coating layer 4B 4B 5B 4B 5B A - - - - - B - - - - - C - - - - - Coating layer 4B 4B 5B 4B 5B Example 3 Coating layer 4B 4B 5B 4B 5B A - - - - - B - - - - - C - - - - - Coating layer 4B 4B 5B 4B 5B Example 4 Coating layer 4B 4B 5B 4B 5B A - - - - - B - - - - - C - - - - - Coating layer 4B 4B 5B 4B 5B Comparative Example 1 - 1B 1B 1B 1B 1B Comparative Example 2 - 1B 1B 1B 1B 1B

In the table above,

AC : acrylic, EA : ethyl acetate, NC : nitro cellulose,

TOL : toluene, MEK : methyl ethyl ketone, EVA : ethylene vinyl acetate,

IPA : Isopropyl Alcohol, VC-VA : Vinyl Chloride-Vinyl Acetate,

CAB : cellulose acetate butyrate.

The porous laminated polyester film of the present invention is a laminated polyester film obtained by biaxially stretching a mixture of inorganic particles, a fluorescent brightener, silica particles, and the like, having excellent light shielding properties, and having a small specific gravity due to evenly distributed micropores in the film. It has excellent texture and excellent whiteness, so it has excellent surface properties as a white film instead of paper when used for various purposes such as printing, imaging, advertising, and exhibition.

Claims (16)

Porous polyester resin layer (B layer) containing incompatible thermoplastic resin in polyester resin, gloss layer mainly composed of polyester resin having 60 degree glossiness of 100% or more of the surface laminated on one side of B layer (Layer A) ), Three-layer porous polyester film of a matte layer (layer C) mainly composed of a polyester resin having a 60-degree glossiness of 50% or less of the surface laminated on the other side of layer B, wherein the density is 0.55 to 1.25 g. A biaxially stretched polyester film having a / cm < 3 > and a coating liquid applied to at least one surface at the same time. The method of claim 1, The layer coated with the coating liquid has an easily adhesive property, an antistatic property, or a release property. The method of claim 2, The biaxially stretched polyester film characterized by the water-soluble coating liquid which has an acryl type, polyester type, or polyurethane type as a main component as a coating liquid for providing easy adhesiveness. The method of claim 2, The biaxially stretched polyester film characterized by the coating liquid which has a silicone type as a main component as a coating liquid for providing mold release property. The method of claim 1, A biaxially stretched polyester film, wherein the thermoplastic resin incompatible with the polyester resin is a polyolefin resin. The method of claim 1, The thermoplastic resin incompatible with the polyester resin is a polystyrene-based resin. The method according to claim 2 or 3, A biaxially stretched polyester film, characterized in that the melt index of the polyolefin resin and the polystyrene resin is 2 to 20 g / min. The method of claim 1, A biaxially stretched polyester film comprising 3 to 30% by weight of an incompatible thermoplastic resin in a polyester resin. The method of claim 1, A biaxially stretched polyester film comprising 5 to 30% by weight of inorganic particles and 0.005 to 0.5% by weight of a fluorescent brightener in the porous polyester resin layer (B layer). In claim 1 glossy layer (A layer), A biaxially stretched polyester film comprising 0.5% by weight or less of silica particles having an average particle size of 0.5 to 5 µm. In the first matte layer (C layer), A biaxially stretched polyester film comprising 0.5 to 10% by weight of silica particles having an average particle size of 1 to 20 µm. In claim 1 glossy layer (A layer), The layer thickness is 1-10 micrometers, The biaxially-stretched polyester film characterized by the above-mentioned. In the first matte layer (C layer), The layer thickness is 1-10 micrometers, The biaxially-stretched polyester film characterized by the above-mentioned. The method of claim 6, The inorganic particles are at least one of titanium dioxide, calcium carbonate, silica, kaolin, mica, talc, and barium sulfate. The method of claim 6, Biaxially stretched polyester film, characterized in that the average particle size of the inorganic particles is 0.1 to 10㎛. The method of claim 6, A biaxially oriented polyester film, wherein the optical brightener is bisbenzoxazole.