KR102135434B1 - Multi layer film having high migration and transparency - Google Patents

Abstract

The present invention is a multi-layer film comprising a skin layer on one or both sides of a base layer and a base layer, wherein the skin layer has an oligomer content of 0.3 to 0.8% by weight, and an intrinsic viscosity of 0.66 to 0.8 ㎗/g of polyester. And, the surface roughness according to KS B 0161 Ra 10 to 30㎚, Rz is 450 to 1,000㎚ relates to a multilayer film.
The multi-layer film according to the present invention has low oligomer properties, has high transparency and surface properties, has good coating properties and workability, and has a small effect of migration of oligomer components. The multilayer film according to the present invention can be effectively used for a carrier sheet including a ceramic sheet, an electrode sheet, etc., as well as an adhesive surface protection film based on these effects.

Description

Multi layer film having high migration and transparency

The present invention relates to a multi-layer film having excellent releasability and transparency, and more particularly, to a multi-layer film having improved transparency and releasability by placing a skin layer having a specific range of oligomer content and intrinsic viscosity on one or both sides of a base layer.

Polyester film (Polyester film) is excellent in the stability of physical properties in a wide temperature range from low temperature to high temperature, excellent chemical resistance compared to other polymer resins, good mechanical strength, surface properties, uniformity of thickness. Therefore, it has excellent applicability in a variety of applications and process conditions, so it has been applied to capacitors, photo films, labels, pressure-sensitive tapes, decorative laminates, transfer tapes, polarizers, and green sheets for mold release. Therefore, the demand is increasing day by day.

Among them, the release film is used as a film for protecting an adhesive surface for an adhesive, an adhesive, and a tackifier, or used as a carrier sheet for forming a sheet of resin, in detail, a ceramic sheet, an electrode sheet, and the like. In recent years, the use and varieties of optical products have diversified and the production volume has increased, and for reasons of productivity improvement, pressure-sensitive adhesives and adhesives are changing from a liquid state to a sheet form.

The release film in the form of a sheet temporarily protects the adhesive adhesive surface of the adhesive article from contamination by dust, debris, moisture and other contaminants, for example, until the label is used.

In general, the release film is separated from the adhesive surface immediately before use of the adhesive product. Therefore, the release film is formed with a coating layer capable of providing adhesion to the product while providing peelability to the surface of the product.

Also, the release film requires high transparency and high roughness. This is not only for checking the adherend to be protected through the release film, but also for inspecting the quality of the release film itself. When the roughness is low, after coating the release layer of the release film, a weak blocking phenomenon occurs in which the adhesion layer and the release film adhere to each other, resulting in coating processability It becomes unstable and causes a problem that the release adhesive force becomes non-uniform.

In order to solve this problem, the Republic of Korea Patent Registration No. 10-1399387, etc. may have an aging step of aging at a high or low temperature after forming a coating layer. However, in the case of polyethylene terephthalate (PET), which is the main raw material of the film, it is easy to deform by moisture or the like by aging during film production, and there is a problem that the oligomer migrates to the surface of the film during aging.

In addition, it is also possible to use a polymer having high heat resistance, such as polyethylene naphthalate or polyimide, as disclosed in Korean Patent Application Publication No. 2005-0032694, but the manufacturing cost is very high compared to that of PET, and it is difficult to post-process.

In addition, it is possible to make a low-oligomeric PET film after solid-phase polymerization of terephthalic acid and ethylene glycol, which are the raw materials of PET, to remove the oligomer, but the manufacturing cost is high during thick film production, it takes a long time for solid-phase polymerization, and powder occurs during polymerization. There is a problem that occurs a lot.

Republic of Korea Registered Patent 10-1399387 (May 20, 2014) Republic of Korea Patent Publication 10-2005-0032694 (April 08, 2005)

The present invention is to solve the problems as described above, has a low oligomer property, has high transparency and surface properties, has good coating properties and workability, and small migration of oligomer components, excellent release property and transparency of the multilayer film. It is aimed at providing.

The present invention relates to a multilayer film having excellent releasability and transparency.

An aspect of the present invention is a multi-layer film comprising a skin layer on one or both surfaces of a base layer and a base layer, wherein the skin layer has an oligomer content of 0.3 to 0.8% by weight, and an intrinsic viscosity of 0.66 to 0.8 ㎗/g. It contains an ester, and relates to a multilayer film having a surface roughness of Ra 10 to 30 nm and Rz of 450 to 1,000 nm according to KS B 0161. At this time, the multi-layer film is characterized in that the transparency (haze) according to JIS K 715 is 0.5 to 5, and the transparency after heat treatment at 150° C. for 30 minutes satisfies the following Equation 1.

[Equation 1]

Transparency (haze) after heat treatment at 150℃ for 30 minutes ≤ Transparency of film before heat treatment × 2

Another aspect of the present invention relates to a multilayer film comprising 400 to 1,800 ppm of inorganic particles with respect to the polyester forming the skin layer. At this time, the inorganic particles are any one or two or more selected from silica, zeolite, kaolin, calcium carbonate, titanium oxide, kaolin and barium sulfate, and the average particle diameter may be 0.5 to 5 μm.

In addition, the multi-layer film in the present invention is characterized in that the total thickness is 15 to 300㎛, the base layer is 70 to 90% by weight compared to 100% by weight of the entire film, and the skin layer is 10 to 30% by weight.

The multi-layer film according to the present invention has low oligomer properties, has high transparency and surface properties, has good coating properties and workability, and has a small effect of migration of oligomer components. The multilayer film according to the present invention can be effectively used for a carrier sheet including a ceramic sheet, an electrode sheet, etc., as well as an adhesive surface protection film based on these effects.

Hereinafter, a multilayer film having excellent releasability and transparency according to the present invention will be described in more detail through specific examples or examples. However, the following specific examples or examples are only one reference for explaining the present invention in detail, and the present invention is not limited thereto, and may be implemented in various forms.

In addition, unless otherwise defined, all technical and scientific terms have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terms used in the description herein are for the purpose of effectively describing specific embodiments only and are not intended to limit the present invention.

Also, the singular form used in the specification and the appended claims may be intended to include the plural form unless otherwise indicated in the context.

The multilayer film according to the present invention may include a base layer and a skin layer formed on one or both surfaces of the base layer.

The base layer may be made of a resin comprising a polyester resin, that is, polyethylene terephthalate, polyethylene naphthalate, polytrimethylene terephthalate, polybutylene terephthalate, etc., of which polyethylene terephthalate is particularly preferred.

The polyethylene terephthalate (hereinafter PET) is made of terephthalic acid and ethylene glycol as a polymerization component, and other components (monomers) may be further copolymerized within a range not impairing the objects and effects of the present invention.

Other copolymerizable components include isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, 5-sodium sulfoisophthalic acid, succinic acid, adipic acid, sebacic acid, dodecane diacid, dimer acid, maleic anhydride, and maleic acid Dicarboxylic acids such as acid, phthalic acid, itaconic acid, citraconic acid, mesaconic acid, cyclohexanedicarboxylic acid, hydroxycarboxylic acid such as 4-hydroxybenzoic acid, ε-caprolactone, lactic acid, 1,3 And polyfunctional compounds such as glycols such as propanediol, 1,6-hexanediol and cyclohexanedimethanol, trimellitic acid, trimesic acid, pyromellitic acid, trimethylolpropane, glycerin and pentaerythritol.

The polyester comprising the PET is polycondensed by a known method, for example, after directly diesterifying a dicarboxylic acid component and a diol component, and then heating the product of this reaction under reduced pressure to remove excess diol component. There is a method for producing by using, or a method for producing by using a dialkyl ester of dicarboxylic acid as a dicarboxylic acid component and transesterifying with a diol component, followed by polycondensation in the same manner as described above. At this time, an alkali metal, an alkaline earth metal, manganese, cobalt, zinc, antimony, germanium, and titanium compounds can be used as a reaction catalyst, if necessary.

Intrinsic viscosity of the polyester constituting the base layer in the present invention is preferably 0.5 to 1.0 mm 2 /g, more preferably 0.6 to 0.8 mm 2 /g. When the intrinsic viscosity of the base layer is less than 0.5 ㎗/g, heat resistance may be reduced, and when it exceeds 1.0 ㎗/g, raw material processing is not easy.

In addition, the thickness of the base layer is not limited, but preferably includes 70 to 90% by weight compared to 100% by weight of the entire multilayer film.

In the present invention, the skin layer may be formed on one side or both sides of the base layer, and preferably on both sides. Further, the skin layer may be formed of one or more multilayers.

The skin layer may be made of the same or different resin as the base layer, preferably polyester, more preferably PET.

The polyester resin forming the skin layer may have an intrinsic viscosity of 0.66 to 0.8 Pa/g. When the intrinsic viscosity of the skin layer is less than 0.66 ㎗/g, it is difficult to control the oligomer content during solid phase polymerization, and the viscosity is too low to control the film thickness during film formation, and when it is more than 0.8 ㎗/g, the viscosity is It is too high to cause interfacial instability during coextrusion, which can make it difficult to form a multilayer film desired in the present invention.

In addition, the polyester resin constituting the skin layer has a surface roughness Ra according to KS B 0161 (definition and display of surface roughness) Ra (arithmetic average roughness, the sum of the upper and lower totals at the center line of the reference length, and the value is measured intervals) Divided by the length of 10 to 30 ㎚ and Rz (10 points average illuminance, 5 in order from the highest mountain, 5 in order from the deepest goal, based on the average line of a specific section among all flat elements within the reference length) To find, average the distance value from the average line of each of the five points and display the difference value). When the Ra value is less than 10 nm or Rz is less than 400 nm, the smoothness is excellent, but scratching or blocking occurs during the coating process, resulting in non-uniform adhesion of the release layer, and when the Ra value is greater than 30 nm or Rz is greater than 1,000 nm When used, the surface of the release film is transferred to the adhesive layer, which affects the final product, resulting in poor quality.

In particular, Rz is important. Ra is difficult to represent the smoothness because the number suddenly increases when coarse particles are present on the surface, but in the case of Rz, it is important to represent the smoothness because it can represent representative values even in unusual situations such as coarse particles.

In addition, the multilayer film according to the present invention may further include inorganic particles with respect to the resin composition forming the skin layer. The inorganic particles are exposed to the surface of the film through a stretching process to perform a role of improving the slipperiness and windability of the film, and are not limited to the type as long as it can be used for the film.

Examples of the inorganic particles include silica, zeolite, kaolin, calcium carbonate, titanium oxide, kaolin and barium sulfate, and any one or a mixture of two or more of them may be used.

The inorganic particles may have an average particle diameter of 0.5 to 5㎛. If the average particle diameter is less than 0.5 μm, the film has too low roughness, which may cause foam dropping or protrusion when winding in the film forming process. If it is more than 5 μm, the smoothness and transparency are poor, and after release coating, it is transferred to the release layer and then transferred to the release layer. The coating adhesion of the product may be deteriorated, and it is difficult to inspect due to the lack of transparency when inspecting after release coating. In addition, the inorganic particles may be included in the 400 to 1,800ppm with respect to the resin composition forming the skin layer. When added to less than 400ppm, the effect of improving slip and windiness due to the addition of inorganic particles is insufficient, and when added to more than 1,800ppm, the transparency of the film is lowered, so it is difficult to use as a release film because quality inspection is not easy during the coating process.

The multilayer film according to the present invention may further include various additives in the resin composition forming the base layer or skin layer, if necessary. Examples of such additives include various weathering agents such as light stabilizers, ultraviolet absorbers and antioxidants, chelating agents, dyes, pigments, viscosity modifiers, plasticizers, reinforcing agents, antistatic agents, catalysts and rust inhibitors.

The multilayer film according to the present invention may have a transparency (haze) according to JIS K 715 of 0.5 to 5. If the transparency is less than 0.5, the film running property is poor, and many scratches may occur, resulting in more defects. Also, the yield may drop because it cannot cover even minute defects that do not affect the quality of the final product. In addition, if it is more than 5, the transparency may be too low for inspection.

In addition, the multi-layer film according to the present invention should satisfy the following formula 1 after the heat treatment at 150 ℃ for 30 minutes.

[Equation 1]

Transparency (haze) after heat treatment at 150℃ for 30 minutes ≤ Transparency of film before heat treatment × 2

When the transparency after heat treatment in Equation 1 exceeds twice the transparency of the film before heat treatment, there are many oligomer migrations, which not only affects the releasing force, but also acts as a defect and may affect the quality of the final product.

The multilayer film according to the present invention is not limited to a manufacturing method, and for example, a resin constituting a base layer is extruded through an extruder, and a resin constituting a skin layer is extruded in another extruder. At this time, it is good to extrude the inorganic particles in the resin constituting the skin layer. The melted extrudate meets at the feed block and is coextruded and then biaxially stretched sequentially after casting and cooling using a cooling drum or the like. At this time, after stretching in the longitudinal direction, it can be stretched and wound in the width direction.

The multilayer film according to the present invention may have a total thickness of 15 to 300 μm, but is not limited thereto. In addition, the base layer may occupy 70 to 90% by weight of the total film 100% by weight, the skin layer may occupy 10 to 30% by weight. In particular, the range occupied by the skin layer in the entire multilayer film is important. When the skin layer is contained less than 10% by weight, it is difficult to form the skin layer itself due to interfacial instability and fracture, and when it exceeds 30% by weight, the release film on the adhesive layer The surface of the product can be transferred, affecting the final product, resulting in poor quality.

Hereinafter, a multi-layer film having excellent releasability and transparency according to the present invention will be described in more detail with reference to Examples and Comparative Examples. However, the following examples and comparative examples are only examples for explaining the present invention in more detail, and the present invention is not limited to the following examples and comparative examples.

The physical properties of the specimens prepared through the following examples and comparative examples were measured as follows.

① Intrinsic viscosity

After adding 0.4 g of a sample sample used in Examples and Comparative Examples to 100 ml of a reagent in which phenol and 1,1,2,2-tetrachloroethanol were mixed at a weight ratio of 6:4, dissolved for 90 minutes, the Uberode Viscometer Transfer to (Ubbelohde viscometer) and hold for 10 minutes in a constant temperature bath at 30°C, and the number of seconds of dropping of the solution was determined using a viscometer and aspirator. In addition, the number of drops of the solvent was also determined under the same conditions, and then RV (Relative viscosity) and IV (Intrinsic viscosity) values were calculated by the following Equations 2 and 3.

[Equation 2]

RV = number of samples falling/solvent falling

[Equation 3]

IV = 1/4(RV-1)/C + 3/4(ln RV/C)

(In the formula 3, C means the concentration of the sample.)

② Oligomer content in film

Chloroform was added to HFIP (1,1,1,3,3,3-hexafluoro-2-propanol), which is a sample solvent, using an oligomer quantitative recovery method (Japanese Polymer Analytical Dictionary), followed by dissolution at room temperature, followed by acetonitrile. (Acetonitrile) is precipitated with a polymer. Then, a calibration curve of a standard material (Cyclic trimer, Formula 1) is prepared using a liquid chromatography (LC) analysis equipment, and then the purity of the cyclic oligomer is determined through sample analysis. As the analysis equipment, LC analysis equipment and Agilent's 1100 Series were used.

[Formula 1]

③ Haze

Specimens were measured using a Haze meter (nipon denshoku, Model NDH 5000) according to JIS K 715.

④ Measurement of surface migration of oligomer in film

First, the specimen measuring Haze was placed in a box with a height of 3 cm, a width of 21 cm, and a height of 27 cm, and the heat treatment was performed at 150° C. for 10 minutes, 20 minutes, and 30 minutes, respectively, to heat the oligomer to the film surface. After migrating, it was left for 5 minutes to measure the Haze value by time. And ΔH was calculated using the following equation (4).

[Equation 4]

△H = Haze of hot air-treated film-Haze of film before hot air treatment

(The higher the △H, the more migration occurred)

⑤ Surface roughness Ra, Rz

Ra (centerline average roughness) and Rz (10 point average roughness) were measured using a two-dimensional contact surface roughness meter (SE3300 manufactured by Kosaka Corporation).

(Example 1)

Polyethylene terephthalate (PET) having an intrinsic viscosity of 0.65 ㎗/g and an oligomer content of 1.3% by weight as a base layer, and a solid phase polymerized PET chip having an intrinsic viscosity of 0.66 ㎗/g and an oligomer content of 0.6% by weight in the skin layer. Used, 1,200 ppm of silica particles having an average particle diameter of 1.6 µm are mixed, co-extruded and cast, respectively, stretched 3 times, 3.3 times in the vertical and horizontal directions, and heat-treated at 230° C. to make a total thickness of 75 μm. A film was prepared. At this time, the base layer was 80% by weight of the total film weight, and the skin layer was 20% by weight, and the surface roughness, Haze, and surface oligomer migration of the film after production were measured and described in Table 2 below.

(Examples 2 to 10 and Comparative Examples 1 to 9)

A specimen was prepared in the same manner as in Example 1, except that the layer composition, intrinsic viscosity, oligomer content, particle size, and particle amount were changed as described in Table 1 below. The surface roughness, Haze, and surface oligomer migration of the films of the prepared specimens were measured and are shown in Table 2 below.

[Table 1]

[Table 2]

As shown in Table 2, it can be seen that Examples 1 to 9 according to the present invention satisfies both the surface roughness and the range of the present invention in the Haze value, and the surface migration measurement of the oligomer has only a slight increase in width compared to the initial Haze. It was found that the elution was less than that of the comparative example. In addition, it can be seen that all of Examples 1 to 9 satisfy Equation 1 above, so that the oligomer migration is small and has favorable flatness for fairness after release coating.

On the other hand, in the case of the comparative example, the surface elution of the oligomer was severe (Comparative Examples 1, 3, 4, 8), or it was often difficult to form a film (Comparative Examples 2, 5, 6), and the Ra and Rz values in the surface roughness were It was found that the workability fell outside the standard range (Comparative Examples 7, 9).

Although the preferred embodiments of the present invention have been described above, it is clear that the present invention can use various changes and equivalents, and can be applied in the same manner by appropriately modifying the above embodiments. Therefore, the above description is not intended to limit the scope of the present invention as defined by the following claims.

Claims (6)

A multi-layer film comprising a skin layer on one or both sides of a base layer and a base layer, wherein the skin layer has an oligomer content of 0.3 to 0.8% by weight, an intrinsic viscosity of 0.66 to 0.8 ㎗/g of polyester, KS A multilayer film having a surface roughness of Ra 10 to 30 nm and Rz of 450 to 1,000 nm according to B 0161. According to claim 1,
The multilayer film has a transparency (haze) according to JIS K 715 of 0.5 to 8 based on a film having a total thickness of 75 um, and a multilayer film in which transparency after heat treatment at 150° C. for 30 minutes satisfies Equation 1 below.
[Equation 1]
Transparency (haze) after heat treatment at 150℃ for 30 minutes ≤ Transparency of film before heat treatment × 2 According to claim 1,
Multilayer film containing 300 to 1,800 ppm of inorganic particles with respect to the polyester forming the skin layer. According to claim 3,
The inorganic particles are multi-layer films of any one or two or more selected from silica, zeolite, kaolin, calcium carbonate, titanium oxide, kaolin and barium sulfate. According to claim 3,
The inorganic particles are multi-layer film having an average particle diameter of 0.5 to 5㎛. According to claim 1,
The multi-layer film has a total thickness of 15 to 300㎛, the base layer is a multi-layer film of 70 to 90% by weight compared to 100% by weight of the entire film, the skin layer is 10 to 30% by weight.