Method for preparing a barrier film

Abstract

The present application relates to a method for preparing a barrier film. The present application can provide a method for preparing a barrier film having excellent barrier characteristics and optical performances. The barrier film produced by the method of the present application can be effectively used not only for packaging material for food or medicine, and the like, but also for various applications, such as LCDs (Liquid Crystal Displays) or a solar cells, substrates for electronic papers or OLEDs (Organic Light Emitting Diodes) or sealing films.

Claims

1. A method for preparing a barrier film comprising a base material film and a barrier layer on the base material film, and the barrier film having a water vapor transmission rate of from 0.005 mg/m.sup.2.Math.day to 2 mg/m.sup.2.Math.day at a temperature of 40° C. and a relative humidity of 90%, the method comprising: forming a polysilazane layer on the base material film; and modifying the polysilazane layer so as to be transformed into the barrier layer by plasma-treating the polysilazane layer in a processing space while injecting water vapor, a discharge gas, and a reaction gas into the processing space, wherein: a percentage of an injection flow rate of injected water vapor, relative to the total flow rate of gases injected into the processing space is maintained to be about 20% or more to about 50% or less during the plasma-treating, wherein the percentage of water vapor being injected is maintained by controlling flow rates of the water vapor, the discharge gas and the reaction gas and wherein the percentage of injected water vapor is determined by the formula 100×A/(A+B+C), the A, B and C being injection flow rates of the water vapor, the discharge gas, and the reaction gas, respectively, and each flow rate has a unit of sccm; wherein a ratio (A/B) of the injection flow rate of the water vapor (A) to the injection flow rate of the discharge gas (B) is maintained at 0.4 or more, the injection flow rate of each having a unit of sccm, and wherein a ratio (A/C) of an injection flow rate of the water vapor (A) to an injection flow rate of the reaction gas (C) is maintained at 0.4 or more, the injection flow rate of each having a unit of sccm.

2. The method for preparing a barrier film according to claim 1, wherein the polysilazane layer is formed by coating a polysilazane coating liquid on the base material film.

3. The method for preparing a barrier film according to claim 1, wherein the polysilazane layer comprises a polysilazane having units of the following Formula 1: ##STR00004## wherein R.sup.1, R.sup.2 and R.sup.3 are each independently a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aryl group, an alkylsilyl group, an alkylamido group or an alkoxy group.

4. The method for preparing a barrier film according to claim 3, wherein each of R.sup.1 to R.sup.3 in Formula 1 is a hydrogen atom.

5. The method for preparing a barrier film according to claim 1, wherein the polysilazane layer has a thickness of 20 nm to 1,000 nm.

6. The method for preparing a barrier film according to claim 1, wherein the plasma treatment is carried out while maintaining a hydrogen partial pressure generated from the water vapor during processing in the processing space at 2.00×10.sup.−5 Pa or more by controlling the injection flow rate of the water vapor in the processing space.

7. The method for preparing a barrier film according to claim 1, wherein a process pressure upon the plasma treatment is maintained in a range of 50 to 500 mTorr.

8. The method for preparing a barrier film according to claim 1, wherein an applied power density upon the plasma treatment is maintained at 0.2 W/cm.sup.2 or more.

9. The method for preparing a barrier film according to claim 1, wherein an energy of the plasma treatment is maintained at 2 J/cm.sup.2 or more.

10. The method for preparing a barrier film according to claim 1, wherein the base material film is a polymer film or a polymer film on at least one surface of which an intermediate layer comprising at least one resin selected from the group consisting of acrylic resin, urethane resin, melamine resin, alkyd resin, epoxy resin, siloxane polymer and condensation product of organosilane compound is formed, and wherein the plasma-treating is performed in a state where the polysilazane layer is in direct contact with the surface of the polymer film or the intermediate layer.

Description

MODE FOR INVENTION

(1) Hereinafter, the preparation method of the present application will be described through Examples and Comparative Examples according to the present application, but the scope of the present application is not limited by the following examples.

Example 1

(2) An intermediate layer having a thickness of about 900 nm was formed on the surface of a PET (poly(ethylene terephthalate)) film having a thickness of about 50 μm, using isocyanurate acrylate. Subsequently, a polysilazane solution (a solution prepared by adding about 4 parts by weight of dimethylethanolamine (DMEA), relative to 100 parts by weight of NN 120 solution, manufactured by AZ Electronics Materials) was coated on the intermediate layer to a thickness of about 120 nm or so. Then, a plasma discharge treatment was performed in a chamber. The discharge treatment was performed while injecting argon gas (discharge gas), water vapor, and oxygen gas (reaction gas) at flow rates of about 150 sccm, about 75 sccm and about 100 sccm, respectively (water vapor pressure: about 23.1%). At this time, the starting pressure of the chamber was set at about 250 mTorr and the pressure was maintained at about 254 mTorr or so during the process. The processing temperature in the process was about 114° C. or so. With regard to the power upon the plasma treatment, the power density per unit area of the electrode was set to be about 1 W/cm.sup.2, and the processing energy was set to be about 12 J/cm.sup.2, by performing the plasma treatment for about 12 seconds or so. A surface layer having a thickness of about 400 nm or so was formed on the surface of the modified polysilazane layer after the modification treatment (plasma treatment) with a known material, and then the water vapor transmission rate (WVTR) was measured to be about 1.94 mg/m.sup.2day. Here, for the water vapor transmission rate, the measuring equipment (MOCON Aquatron 1) was performed in a known manner.

Example 2

(3) A barrier film was prepared in the same manner as in Example 1, except that the water vapor injection flow rate was changed to about 100 sccm upon the plasma treatment (water vapor pressure: about 28.6%). The water vapor transmission rate (WVTR) was measured in the same manner as in Example 1 to be about 1.6 mg/m.sup.2day.

Example 3

(4) A barrier film was prepared in the same manner as in Example 1, except that the water vapor injection flow rate was changed to about 125 sccm upon the plasma treatment (water vapor pressure: about 33.3%). The water vapor transmission rate (WVTR) was measured in the same manner as in Example 1 to be about 1.18 mg/m.sup.2day.

Example 4

(5) A barrier film was prepared in the same manner as in Example 1, except that the water vapor injection flow rate was changed to about 90 sccm (water vapor pressure: about 26.5%) upon the plasma treatment and no surface layer was formed after the plasma treatment. The water vapor transmission rate (WVTR) was measured in the same manner as in Example 1 to be about 2.2 mg/m.sup.2day.

Comparative Example 1

(6) An intermediate layer having a thickness of about 900 nm was formed on the surface of a PET (poly(ethylene terephthalate)) film having a thickness of about 50 μm, using isocyanurate acrylate. Subsequently, the same polysilazane solution as used in Example 1 was coated on the intermediate layer to a thickness of about 120 nm. Then, the coating layer of the polysilazane solution was maintained in a constant temperature and humidity chamber at 85° C. and 85% relative humidity atmosphere for about 3 hours and subjected to a moisture-heat hardening treatment. A surface layer having a thickness of about 400 nm or so was formed on the surface of the modified polysilazane layer after the modification treatment (moisture-heat hardening treatment), and then the water vapor transmission rate (WVTR) was measured to represent a water vapor transmission rate of more than about 5,000 mg/m.sup.2day

Comparative Example 2

(7) The polysilazane layer subjected to the moisture-heat hardening treatment in Comparative Example 1 was further subjected to a plasma treatment. The conditions where the plasma treatment was performed were the same as in Example 1, except that no water vapor was injected. A surface layer having a thickness of about 400 nm or so was formed on the surface of the modified polysilazane layer after the plasma treatment, and then the water vapor transmission rate (WVTR) was measured to be about 44 mg/m.sup.2day.

Comparative Example 3

(8) A barrier film was prepared in the same manner as in Example 1, except that no water vapor was injected upon the plasma treatment (water vapor pressure: 0%). The water vapor transmission rate (WVTR) was measured in the same manner as in Example 1 to be about 2.6 mg/m.sup.2day.