KR100562464B1 - Surface Treatment Biaxially Stretched Film - Google Patents

Abstract

The present invention is a biaxially stretched surface treatment prepared by applying an acrylic resin as a main component and applying a primer composition containing 0.1 to 10% by weight of inorganic fine particles or higher fatty acid wax to at least one side of a polyester film at 0.005 to 0.1 g / m 2. The present invention relates to a film, which solves problems caused by maintaining the transparency of the film by using a functional resin and evenly distributes the functional resin aqueous solution evenly by using a conventional tenter method to the film with improved transparency. It can give thickness and physical property, and can improve manufacturing operation.

Primer, Polyester Film, Inorganic Particles

Description

Surface-treated biaxially oriented film {Pretreated biaxially oriented film}             

The present invention relates to a surface-treated biaxially oriented film, and more particularly, a primer composition containing an acrylic resin as a main component and an inorganic particle added within 0.004% is applied to at least one surface of a polyester film at 0.005 to 0.1 g / m 2. It relates to the produced film.

In general, polyester, especially polyethylene terephthalate (abbreviated as PET) has a stable structure, chemically stable, high physical and mechanical strength, excellent heat resistance, durability, chemical resistance and electrical insulation, magnetic recording media It is widely used for various medical, industrial, and molded products in addition to materials for capacitors, capacitors, electrical insulation materials, and packaging materials.

Recently, when used as graphic materials and various post-processing materials, in order to give new functionality to existing polyester films, a copolyester film is prepared, a corona treatment on the surface of the film, or a chemical is applied as a primer. have.

Among these methods, a method of applying a chemical material to add a new function to the film surface is the most widely used method in the industry.

The most representative of the functions of a polyester film coated with a primer having a function on the surface of the film produced in this way is, firstly, this printing function for improving the printability between the ink and the polyester film, and second, various special functions. Eggplants are used to provide adhesion to materials applied to make post-processed products, eg films for transparencies, or films for diagnosing lasers or inkjet printers, or films for diazos. Heat sealing function for use in mining, antistatic function, which is an essential function of polyester film for protecting various graphic films and electronic materials, and release function to easily peel off chemicals applied on polyester film. There is a slippery to improve workability.

In recent years, the demand for high-quality films with high transparency is increasing. Such films have less inorganic particles, which have a high coefficient of friction and poor activity, which causes severe blocking, which not only handles the film but also forms the film. Difficulties in processing and slitting are involved. In order to secure such a problem, it is necessary to apply a primer to give a function of the active activity, but such a film is excellent in transparency, the nonuniformity of the application is prominent and the stretching nonuniformity occurs accordingly.

In order to prepare a polyester film coated with a functional primer, it is common practice to apply emulsion polymers or water-soluble or water-dispersible polymers after longitudinal stretching before entering transverse stretching. At this time, in order to stretch three times or more in the transverse direction in the tenter, the aqueous solution applied to the sheet is dried, and at the same time, the sheet is preheated and heated to a glass transition temperature (Tg) or higher suitable for stretching. During the drying and preheating process, the primers applied to the sheet must be uniformly dried as well as the sheet must be crackedly heated so that the stretching can be uniform to produce a high quality polyester film.

If the drying and stretching are not uniform First, the thickness of the product is poor and the thickness of the coating layer is uneven to obtain the desired physical properties uniformly; Second, the decrease in stress at break and heat shrinkage of the final film ), Etc. may increase.

However, when the drying of the aqueous solution and the preheating of the sheet at the same time as the hot air in the tenter as described above, hot air is directly contacted with the coating layer before the aqueous solution is completely dried. In addition, since the sheet is not preheated uniformly, there is a considerable problem in producing a polyester film having a uniform physical property since the lateral stretching is not uniform. In addition, since the vapor evaporated from the aqueous primer solution and the hot air supplied from the outside coexist in the tenter, there is a problem that a temperature gradient occurs, thereby preventing preheating and stretching uniformly.

Furthermore, in the conventional polyester film manufacturing method, the drying and preheating must be performed simultaneously in a tenter having a short heating zone in which only the sheet is heated. Therefore, an excessive amount of hot air must be supplied at a high temperature to supply sufficient heat. The breakage occurs frequently during film formation due to the difference in specific heat and draw ratio between the portion applied to the sheet surface and the uncoated portion, resulting in a decrease in production rate.

To improve this, there are methods of extending the heating zone by lengthening the inlet of the tenter, or applying a preheating drying device such as an IR heater after applying a primer, and then transverse stretching after drying. There is a problem that costs a lot of rain or installation.

The present invention solves the problems caused by maintaining the transparency of the film by using a functional resin, even if the existing tenter method to the film with improved transparency evenly distributed functional aqueous solution of the resin can be uniform thickness and physical properties on the film It is an object of the present invention to provide a biaxially oriented film capable of providing a film and improving manufacturing operability.

The biaxially oriented film of the present invention for achieving the above object is 0.005 to 0.1g of a composition containing an acrylic resin as a main component and 0.1 to 10% by weight of inorganic fine particles or higher fatty acid wax is added to at least one side of the polyester film. It is characterized by that it is produced by coating at / ㎡.

The present invention relates to a biaxially stretched polyester film to which an in-line coating method with excellent biactivity and improved transparency is applied.

The polyester film has a high coefficient of friction, which is poor in activity and causes severe blocking, resulting in not only handling of the film but also difficulties in the process of winding and slitting the film.

In order to solve this problem, an inorganic compound such as titanium dioxide, silica, and calcium carbonate is added to the inside of the film to form irregularities on the outside of the film. However, this external particle does not exhibit the effect when the addition amount is small, there is a disadvantage that greatly decreases the transparency of the film when the use amount is large.

The reason why the transparency is poor when the external particles are added is that the compatibility between the polyester and the inorganic material is poor, and thus voids nearly 10 times that of the inorganic compound are generated during the stretching process, and the optical path is changed due to the voids.

In order to solve the problem caused by reducing the amount of external inorganic particles used for transparency of the film, a primer is applied on the surface of the film to impart the activity to the film.

In the present invention, in order to ensure transparency, the inorganic particles used as external particles are not added or lowered to 50 ppm or less, which is much smaller than the amount of internal particles for general packaging. At this time, the particles used are inorganic compounds such as spherical silica, calcium carbonate, porous silica, alumina, silica-alumina, titania, zirconia and the size is about 0.2 to 4㎛.

Usually, a polyester film is obtained by carrying out biaxial stretching after melt-extruding the polyester chip whose particle | grains contain the ethylene terephthalate or ethylene 2,6-naphthalate structure as a main repeating unit. That is, the polyester is extruded at a high temperature of 300 ° C. or higher, and then cooled to room temperature using a casting drum in which cooling water is circulated to prepare an amorphous polyester sheet. Alternatively, the biaxially stretched polyester film is stretched three times or more in the same direction as the moving direction of the sheet by using the rolls arranged laterally, and then three times or more in the tenter capable of preheating the uniaxially stretched sheet with hot air. Manufacture.

In order to prepare a polyester film coated with a primer as in the present invention, the polymer in the emulsion state or the water-soluble or water-dispersible polymer is coated on one side or both sides after longitudinal stretching before entering transverse stretching. When the primer is applied to the polyester sheet, it is common to apply a very diluted aqueous solution or a water dispersible solution, and the solid content of the primer is about 1-10% by weight, and preferably 2-6% by weight. In order to stretch the sheet coated with the primer three times or more in the transverse direction in the tenter, the aqueous solution applied to the sheet should be dried, and at the same time, the sheet should be preheated and heated above the glass transition temperature. It has higher glass transition temperature than the sheet, so it needs to be preheated to 110 ~ 130 ℃.

During this drying and preheating process, not only the drying of the aqueous solution applied to the sheet should be uniform, but also the sheet must be uniformly heated to extend the uniformity to produce a polyester film coated with a high quality primer.

Corona treatment is performed on the surface of the film by using a corona discharger to the uniaxial stretched film prepared for this to have a surface tension of 50 dyne / cm or more, preferably 50-56 dyne / cm. And an aqueous primer solution or aqueous dispersion is applied with a Wet Thickness of 1-6㎛ and dried in a tenter with hot air.

At this time, if the surface tension of less than 50dyne / cm when using the hot air method of the existing tenter drying of the applied aqueous solution is not uniform, the sheet is also not uniformly heated. In addition, the application of the primer aqueous dispersion is also applied to the wet thickness of 6㎛ or more to evaporate the moisture, so the existing tenter is insufficient heat amount, due to the difference in specific heat and elongation ratio of the dried part and the undried part on the sheet surface. Iii) Frequent breaks occur during the process, resulting in lower production rates.

As such, the physical properties of the inline-coated polyester film manufactured using the existing tenter should satisfy the following ranges. The physical properties of the films presented herein are not limited to films having a thickness of 75 μm. In the following, the properties are merely to provide specific data, and for films of all thicknesses, they should exhibit the same tendency as described below.

19.0 ≤ longitudinal strength ≤ 21.0 [Kgf / ㎣]

21.0 ≤ lateral strength ≤ 22.0 [Kgf / ㎣]

  160 ≤ longitudinal elongation ≤ 170 [%]

  135 ≤ transverse elongation ≤ 145 [%]

11.0 ≤ longitudinal F-5 value ≤ 12.0 [Kgf / ㎣]

10.0 ≤ F-5 value in the transverse direction ≤ 11.0 [Kgf / ㎣]

In addition, the orientation of the polyester film coated with the biaxially stretched primer should satisfy the following conditions.

1.640 ≤N _MD ≤ 1.650 -------------- (1)

1.660 ≤N _TD ≤ 1.670 --------------- (2)

0.480 ≤f1≤ 0.500 --------------- (3)

0.550 ≤f2 ≤ 0.570 --------------- (4)

Where N _MD is the refractive index in the longitudinal direction, N _TD is the refractive index in the transverse direction, f1 is the orientation of the amorphous portion in the longitudinal direction, and f2 is the orientation of the amorphous portion in the transverse direction.

This is because if the polyester film to which the primer is applied satisfies the above conditions, the film thus produced can be judged to be stretched in a moderately heated state when the film is produced through transverse stretching and longitudinal stretching.

If the biaxially stretched film does not satisfy the above orientation condition, the physical properties of the final film are reduced. That is, in the polyester film coated with a normal primer, the transverse stretching after the longitudinal stretching is not sufficient, resulting in deterioration of the physical properties in the longitudinal direction.

Longitudinally stretched polyester film should be transversely stretched in a sufficiently preheated state. However, when the primer is applied, sufficient heat is transferred to the film because the sheet is preheated after evaporating the moisture contained in the primer. . Due to this phenomenon, insufficient lateral stretching can result in a decrease in stress at break and an increase in heat shrinkage of the final film. Therefore, the film to which the primer is to be applied should have a balanced orientation in the longitudinal and transverse directions.

Among the above alignment conditions, (1) and (2) are values that include both the crystalline part and the amorphous part, and when the value of (1) becomes higher than this standard or (2) becomes lower than the standard, the stretching in the transverse direction is performed. It will rise small and cause a decrease in strength in the transverse direction. Also, the values of (3) and (4) indicate the degree of orientation of the amorphous portion. If the value of (3) is higher than this criterion or (4) is lower than this criterion, the elongation will be small. It may cause a decrease in strength.

However, after longitudinal stretching according to the present invention by performing a corona treatment on the surface of the film using a corona discharger to the uniaxially stretched film, and adjusting the coating amount of the aqueous primer solution with a Wet Thickness of 1-6㎛ It is possible to produce a high quality film with excellent transparency without lowering and lowering the production rate.

At this time, the resulting film is also very low surface roughness of the pulley film because it does not add the external inorganic particles or significantly reduced the amount to increase the transparency. The final thickness of the produced film is 11-150 μm, and 2D RA (2 dimentional roughness) is 20 nm or less, 3D RA (3 dimentional roughness) and 3D RMS (3 dimentional root mean square) satisfy the conditions of 10 nm or less, respectively. Done.

If the amount of the external inorganic particles is large, the film activity such as coefficient of friction or slitting is improved, but the transparency of the film is not significantly satisfied without satisfying the conditions of 2D RA, 3D RA, and 3D RMS.

The main component of the primer composition applied to impart this activity is a water-dispersible acrylic resin having a glass transition temperature of 20 to 40 ° C., and the coating amount of the resin is about 0.005 to 0.1 g / m 2. The component of the resin is a copolymer acrylic emulsion such as methyl methacrylate, butyl acrylate and hydrooxyethyl methacrylate, and the number average molecular weight of the acrylic emulsion is 15,000 to 20,000. The aqueous solution or water-dispersible primer crude liquid diluted with solvent (ion-exchanged water) has a viscosity of 1.5 to 2.0 cps and a pH of 8.0 to 10.0.

Incorporate inorganic particulates or higher fatty acid waxes to lower the film's coefficient of friction. The content of the inorganic fine particles and the higher fatty acid wax (wax) in the active layer is 0.1 to 10% by weight, preferably 0.5 to 5% by weight.

The inorganic fine particles used are inorganic compounds such as spherical silica, calcium carbonate, porous silica, alumina, silica-alumina, titania, and the size thereof is 0.03 to 0.5 탆, preferably 0.05 to 0.2 탆.

In addition, the water-dispersible higher fatty acid wax used is polyolefin-based, but has various chemical structures. Preferably, the molecular weight is not particularly limited to polyethylene wax and polypropylene wax, and is preferably 500 to 50,000.

If the amount of the inorganic particles or the amount of wax is too small here does not help the activity of the film, such as the coefficient of friction. On the contrary, if the amount of the inorganic fine particles is too high, the transparency of the film is lowered. If the amount of the wax is too large, the adhesion strength is weakened or the moisture resistance is not good, so an appropriate amount is required.

In the film having the above structure, the coefficients of friction between the top surface and the bottom surface have a value of 0.6 or less in both μK and μS (static friction and dynamic friction), and do not cause difficulties in the process of winding up the film and slitting. The haze of the film is 1.0 or less.

As a method of applying the composition of the present invention, a general coating method such as gravure roll coating, mayer bar coating, reverse roll coating, dip coating, slot coating, air knife coating, and the like may be used. It carried out by the following method.

<Evaluation Method of Film Properties>

1. Mechanical Properties

Stress at break, tensile rate, and F-5 values were measured based on ASTM D882-91 using a universal testing machine. Detailed conditions are as follows.

      Cross Head Speed (mm / min.): 500

      Sample width (mm): 15

      Sample length (mm): 50

Here, stress at rupture: stress when the sample ruptures during the tensile test

Tensile rate: The degree of stretching until the sample ruptures

F-5 value: Stress at 5% stress

2.N _MD , N _TD , f1, f2

The Abbe refractometer is used to measure the refractive indices N _{MD and} N _TD in the longitudinal and transverse directions. Substitute these into the Samuels equation to obtain the values of f1 and f2 excluding the influence of the crystal parts.

3. Surface Roughness

3D: Measured by TOPO 3D three-dimensional surface roughness meter manufactured by WAKO of Japan. Preferable 3D RA, 3D RMA is 10 nm or less

2D: Japan KOSAKA LABORATORY LTD. Measured by Surfcoder SE-3300, the preferred 2D RA is less than 20 nm

4. Wetting Tension

As specified in ASTM D-2578, formamide and ethylcellulose parts are mixed in an appropriate ratio to prepare a surface tension measurement solution. Surface tension measurement liquid has a value of 30-58, and the unit is dyne / cm.

After applying the prepared surface tension measurement solution to the surface of the sample by using a cotton swab about 100-150mm, if the reagent shrinks in the center part within 2 seconds, use the reagent below one step. If not, find the reagent shrinking in 2 seconds using the reagent in one step and read the value of the applied reagent to indicate the surface tension value.

5. Uniformity of application

A 200mm × 200mm size sample is placed on the light source and the riser, and the sample is visually seen on the analyzer to examine the uniformity of the primer applied to the sample using the contrast created by the light path difference.

The light from the light source is monochromatic light with λ = 500 nm. When the monochromatic light polarizes through the plaiser and passes through the polyester film coated with a primer, an optical path difference is generated depending on the amount applied. This optical path difference causes light and darkness to pass through the analyzer. After examining the difference in contrast, the surface tension values can be compared to examine the uniformity of the applied primer.

Γ = 2 / λ ---- ⑴

Γ = λ ---- ⑵

When the path difference (Γ) of light satisfies ⑴, constructive interference occurs, the light passing through the analyzer appears bright, and when the path difference (Γ) satisfies 일어나, offset interference occurs, causing the light passing through the analyzer to appear dark. do.

6. Friction Coefficient

A friction coefficient measuring device manufactured by Toyo Seiki Co., Ltd., Japan, was used in accordance with ASTM D1894-78, and measured using a prescribed sled having a load of 200 ± 5 gr. Preferred friction coefficient is μK, μS mode 0.6 or less

7.HAZE

Measured by NDH 1000DP from DENSHOKU KOGYO in Japan, the preferred HAZE is 1.0 or less

Next, the present invention will be described in more detail with reference to preferred embodiments of the present invention. However, the following examples are merely provided to more easily understand the present invention, and the present invention is not limited to these examples.

Example 1

A polyester chip containing 0.003% by weight of external inorganic particles (amorphous silica) having an intrinsic viscosity of 0.60-0.65 and an average diameter of 1.4 μm, using dicarboxylic acid and diol as a main component, is extruded at a high temperature of about 250-300 ° C. Then, it was cooled to about 25-30 ° C. using a casting drum in which cooling water was circulated to prepare an amorphous polyester sheet.

The amorphous polyester sheet was stretched 3.7 times in the longitudinal direction using rolls arranged vertically or horizontally at a temperature above the glass transition temperature, ie, in the range of 95-120 ° C., to prepare a uniaxially stretched film.

The monoaxially oriented film thus prepared is subjected to corona treatment on one surface of the film using a corona discharger to give a surface tension of about 50-56 dyne / cm.

99% by weight of methyl methacrylate copolymer resin and 1% by weight of 50-100 nm inorganic fine particles (spherical micro-silica) were dissolved in ion-exchanged water using a Mayor bar (# 3) on a corona-treated uniaxially stretched film. The coating was applied to have a Wet Thickness of μm.

At this time, the primer solid content of the composition diluted in ion-exchanged water was about 3-5% by weight, the ion-exchanged water was 95-79% by weight, and the final amount applied to the biaxially stretched film was about 0.03-0.04 g / m 2.

The applied composition was dried in a tenter heated by hot air and the film was preheated. The temperature of the tenter was 120-130 ° C., the hot wind speed was 25-30 m / sec, and the wind speed was not faster than 30 m / sec.

The dried and preheated film was stretched 4.1 times in the transverse direction at 130 to 140 ° C., and then heat treated and thermally cured at 200 to 240 ° C. in the heat treatment section divided into five or more stages to obtain a biaxially stretched polyester film coated with a primer. Prepared.

At this time, the final thickness of the film was 75㎛. The physical properties of the produced film were measured according to the above evaluation method, and the results are shown in Table 1 below.

Example 2)

A biaxially stretched polyester film was prepared in the same manner as in Example 1 above. At this time, however, a polyester chip containing no external inorganic particles was prepared. And the primer solid content of the composition diluted in ion-exchanged water was about 5-6% by weight, the ion-exchanged water was 95-79% by weight, and the final amount applied to the biaxially stretched film was about 0.04-0.06 g / ㎡.

Example 3

A biaxially stretched polyester film was prepared in the same manner as in Example 1 above. However, at this time, a corona treatment is performed on the surface of the film by using a corona discharger on both sides of the uniaxial stretched film to have a surface tension of about 50-56 dyne / cm. The double-sided corona treated uniaxially stretched film was coated with a Wet Thickness of 2-3 μm using a Meyer Bar (# 2.5). The final amount applied to the biaxially stretched film was about 0.02-0.03 g / m 2 on each side.

Comparative Example 1)

A biaxially stretched polyester film was prepared in the same manner as in Example 1 above. At this time, the corona-treated biaxially stretched film is coated with a Wet Thickness of 5-10 μm using an aqueous solution or an aqueous dispersion containing a primer using a Mayer bar (# 5).

The final amount applied to the biaxially stretched film was 0.05-0.06 g / m 2. It was. The physical properties of the produced film were measured according to the above evaluation method and are shown in Table 1 below.

Comparative Example 2)

A biaxially stretched polyester film was prepared in the same manner as in Example 1 above. At this time, a polyester chip containing 0.020% by weight of external inorganic particles (amorphous silica) was prepared to prepare a biaxially oriented film.

Comparative Example 3)

A biaxially stretched polyester film was prepared in the same manner as in Example 1 above. In this case, however, inorganic fine particles (spherical micro silica) were not added to the coating composition.

Comparative Example 4)

A biaxially stretched polyester film was prepared in the same manner as in Example 1 above. At this time, the monoaxially oriented film was subjected to corona treatment on the surface of the film using a corona discharger to give a surface tension of about 40-50 dyne / cm, and then an aqueous solution or an aqueous dispersion containing the primer was applied.

Example Comparative example One 2 3 One 2 3 4 Internal Particles (ppm) 30 Nil 20 40 200 50 60 Stress at Break (kg / ㎣) Longitudinal direction 20.1 20.3 20.3 21.3 20.4 20.2 21.0 Transverse 21.8 21.5 21.7 20.6 21.5 20.3 20.5 % Elongation Longitudinal direction 170.0 168.2 169.5 151.3 169.0 169.5 155.5 Transverse 140.5 144.5 141.0 151.0 142.0 142.5 152.5 F-5 value (kg / mm2) Longitudinal direction 11.3 11.8 11.5 12.0 11.3 11.4 12.0 Transverse 10.7 10.2 10.3 10.2 10.7 10.7 10.2 N _MD 1.649 1.650 1.646 1.654 1.648 1.649 1.655 N _TD 1.669 1.668 1.669 1.663 1.670 1.669 1.663 f1 0.488 0.490 0.482 0.509 0.487 0.489 0.510 f2 0.561 0.570 0.561 0.554 0.561 0.560 0.554 Film Surface Roughness (nm) 2D RA 15 5 10 18 22 20 21 3D RA 8 4 6 9 13 11 12 Coefficient of friction μS <0.6 <0.6 <0.4 <0.6 <0.4 > 0.6 <0.6 μK <0.6 <0.6 <0.4 <0.6 <0.4 > 0.6 <0.6 Haze (%) 0.6 0.4 0.9 0.8 1.2 0.3 0.7 Coating uniformity Good Great Good Bad Good Great Bad Workability (breaks) Good Good Great Bad Good Bad Bad

As described in detail above, the biaxially stretched film of the present invention solves the problems caused by maintaining the transparency of the film by using the functional resin, and evenly using the conventional tenter method on the film with improved transparency, evenly the functional resin aqueous solution. There is an effect that can be distributed to give the film a uniform thickness and physical properties and to improve the manufacturing operation.

Claims (5)

A surface-treated biaxially oriented film prepared by applying an acrylic resin as a main component and applying a primer composition containing 0.1 to 10% by weight of inorganic fine particles or higher fatty acid wax to at least one side of a polyester film at 0.005 to 0.1 g / m 2. The surface treatment biaxially oriented film according to claim 1, wherein the following physical properties are satisfied. 19.0 ≤ longitudinal strength ≤ 21.0 [Kgf / ㎣] 21.0 ≤ lateral strength ≤ 22.0 [Kgf / ㎣]   160 ≤ longitudinal elongation ≤ 170 [%]   135 ≤ transverse elongation ≤ 145 [%] 11.0 ≤ longitudinal F-5 value ≤ 12.0 [Kgf / ㎣] 10.0 ≤ F-5 value in the transverse direction ≤ 11.0 [Kgf / ㎣] The surface-treated biaxially oriented film according to claim 1 or 2, wherein the following orientation conditions are satisfied. 1.640 ≤N _MD ≤ 1.650 1.660 ≤N _TD ≤ 1.670 0.480 ≤f1≤ 0.500 0.550 ≤f2 ≤ 0.570 Where N _MD is the refractive index in the longitudinal direction, N _TD is the refractive index in the transverse direction, f1 is the orientation of the amorphous portion in the longitudinal direction, and f2 is the orientation of the amorphous portion in the transverse direction. The surface-treated biaxially oriented film of claim 1, wherein the inorganic fine particles are at least one selected from the group consisting of spherical silica, calcium carbonate, porous silica, alumina, silica-alumina, and titania. The surface-treated biaxially oriented film according to claim 1, wherein the surface roughness of the film is added to within 0.004% by weight, so that 2D RA is 20 nm or less, and 3D RA and RMS are each 10 nm or less.