KR20080062597A - Process for preparing plastic substrate - Google Patents

Abstract

A method for manufacturing a plastic substrate is provided to form middle layers with improved adhesive force on a plastic base film and change a refractive index of a thin film effectively without changing various process variables, thereby improving the thin film of high density with different refractive indexes and improving gas barrier properties and an optical transmission rate. Protection layers(21) are formed in the section of a plastic base film(24). The protection layers are made from an acrylate photo-curable coating material. The protection layers are formed in the outline of gas blocking layers(22). Middle layers(23) are formed to improve adhesive force between the gas blocking layers and the plastic base film. The gas blocking layers are formed by controlling the flux of nitrogen without changing the degree of a vacuum in a reactive system and depositing the film material of plural layers in a direction that a refractive index is gradually decreased.

Description

Process for preparing plastic substrate

1 illustrates a conventionally manufactured plastic film substrate,

2 is a schematic diagram showing the behavior of light passing through two substrates having different refractive indices, where n ₁ is the refractive index of air, n ₂ is the refractive index of a thin film, and n ₃ is the refractive index of a plastic substrate.

3 is a schematic diagram showing the principle of a low reflection film,

4 and 5 show a plastic film substrate manufactured according to the present invention,

6 is a light transmittance measurement results of Examples and Comparative Examples,

FIG. 7 compares a bare film with light transmittance measurement values at 550 nm of each Comparative Example and Example. FIG.

<Detailed Description of Drawings>

1, 11, 21: protective layer (organic or organic-inorganic hybrid coating)

2, 12, 22: gas barrier layer (gas barrier film)

3, 13, 23: intermediate layer (organic or organic-inorganic hybrid coating)

4, 14, 24: plastic base film

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to film substrates for flat panel displays and electronic papers, and more particularly, to control the nitrogen flow rate in a plasma vapor deposition (CVD) method for forming an inorganic oxide thin film or an inorganic oxide thin film on a plastic film substrate. By changing the refractive index of the deposited oxide thin film to increase the light transmittance of the plastic film, and relates to a method for producing a film substrate for flat panel display and electronic paper formed with an inorganic thin film layer having a high level of gas barrier properties.

Flat panel displays, typified by liquid crystal displays, have used glass as a substrate. Displays based on glass substrates are not only limited in design, but also susceptible to impact and limited in thickness and weight. In order to make up for the shortcomings of such glass substrates, development of plastic substrates has been required. The plastic substrate is lighter and thinner than 1/3 of the glass substrate and 1/6 of the weight, and has excellent impact resistance. Materials used for plastic substrates include polyethylene terephthalate (PET), polyethersulfone (PES), polycarbonate (PC), polyarylate (Par), and cyclic olefin copolymer (COC). It is generally used as an optical film. However, plastic films have a lower light transmittance than glass substrates, and have a high gas permeability such as oxygen and water vapor, so that gas melts into the liquid crystal layer through the film surface in a short time to generate bubbles in the liquid crystal, or to break electrodes. Has been a factor of degrading the quality of the display.

In order to compensate for these disadvantages, gas barrier thin films (metal and metal oxide thin films or polymer thin films having barrier properties) should be formed on the plastic substrate film used for the display to minimize gas permeability as much as possible. In order to satisfy conditions such as hardness and heat resistance, a transparent inorganic film has been generally coated. As a method of coating such an inorganic film on a plastic film, a vacuum deposition method such as CVD and physical vapor deposition (PVD), which are dry coating, and a wet coating method have been used.

However, when forming a metal or metal oxide thin film as a gas barrier film by the vapor deposition method, it is necessary to process at high temperature in order to form a stable film. In addition, since such a thin film reduces the light transmittance, its use is limited to the optical film. Concepts of low or antireflective films are disclosed in a number of existing patents. In general, as can be seen in Figure 2, the incident light is partially transmitted and partially reflected at some surface. The manufacture of low or antireflective films is made using the principle of minimizing the reflected light on the basis of the optical theory of destructive interference, which is shown in FIG. A separate thin film with a thickness corresponding to +1/4) λ is required. Therefore, thin films having various refractive indices and thicknesses are required to minimize reflection of light having various wavelengths λ emitted from the light source of the liquid crystal display. In the existing patent, inorganic films were deposited using different materials having different refractive indices to form a separate thin film having such a thickness. However, this method has the disadvantage of having to form a vacuum several times in order to change the process. Some patents have also described thin films with different refractive indices by varying the partial pressure ratios of oxygen and inorganic derivatives. However, even at this time, there are disadvantages in that two or more process variables are changed at the same time.

An object of the present invention is to adjust the ratio of oxygen or nitrogen and organic components (carbon) in a single inorganic film, the refractive index in the inorganic film is continuously changed, accordingly the reflectance is significantly reduced, the light transmittance is improved, between the intermediate layer and the inorganic film It is to provide a plastic film substrate for display and electronic paper, characterized in that the adhesion of the improved to improve the durability and gas barrier properties of the inorganic film.

The present invention includes the step of depositing a composite inorganic precursor containing a hydrocarbon and a reaction gas on one or both sides of the transparent plastic substrate film by plasma chemical vapor deposition to form an inorganic thin film, the step of increasing the nitrogen flow in the plasma chamber It provides a method for producing a plastic substrate, characterized in that carried out under the conditions.

The inventors have surprisingly found that in plasma chemical vapor deposition, an inorganic thin film in which the carbon content of the inorganic thin film is continuously changed can be formed only by controlling the nitrogen flow rate without changing other process variables such as the vacuum of the reaction chamber and the ratio of inorganic derivatives. Revealed.

The conditions for increasing the nitrogen flow rate are not particularly limited, but the range of the nitrogen flow rate is 500 sccm or less, preferably 10 to 120 sccm, more preferably 25 to 75 sccm, and the increase in the nitrogen flow is continuously Or discontinuously increased. When the nitrogen flow rate is continuously increased, the nitrogen flow rate is increased at a constant rate such as 25 sccm / min, and in some cases, depending on the time, so as to be in a range of 500 sccm or less, preferably 120 sccm or less. This means increasing the nitrogen flow rate. In addition, the case where the nitrogen flow rate is discontinuously increased, for example, means a case where the deposition process is performed for 1 minute while the nitrogen flow rate is increased to 0 sccm, 25 sccm, 50 sccm and 75 sccm. The rate of increase of the nitrogen flow rate is not particularly limited, but considering the appropriate change in the film properties, it is preferably 15 to 25 sccm / min.

In addition, in the production method according to the present invention, a composite inorganic precursor and a reaction gas containing a hydrocarbon which is a raw material of the chemical vapor deposition method are specified by the following.

The complex inorganic precursor containing the hydrocarbon is hexamethyldisiloxane, hexamethyldisilazane, tetraethoxysilane, tetramethoxysilane, methoxytrimethylsilane, tetramethylsilane, triphenylsilane, tetrachlorosilane, trichloromethyl From the group consisting of silane, trimethylchlorosilane, dimethyldichlorosilane, dimethylchlorosilane, pentakisdimethylamino tantalum, pentaethoxy tantalum, titanium isopropoxide, titanium butoxide, zirconium tetrachloride and zirconium tetra-tert-butoxide Preference is given to using at least one selected.

In addition, the reaction gas preferably contains oxygen, nitrous oxide or ammonia. The ratio of nitrogen gas / reaction gas is in the range of 0 to 100, preferably 0 to 40, and more preferably 0 to 15, so as to form a film having various conditions from the soft film to the hard film. Can be.

The plastic base film may be formed of a thermoplastic resin such as polyethylene terephthalate, polyether sulfone, polycarbonate, polyimide, polyarylate, or a thermosetting resin such as an epoxy resin or an unsaturated ester resin. However, it is not limited thereto.

In addition, the inorganic thin film according to the present invention is preferably a metal oxide, a metal oxide or a metal nitride including one or two or more metals selected from the group consisting of Si, Ta, Ti and Zr.

The method of manufacturing a plastic substrate according to the present invention further includes a step of pretreating one or both sides of the transparent plastic base film with oxygen, argon, or nitrogen plasma before forming the inorganic thin film in order to improve adhesion with the inorganic thin film. It is desirable to.

In addition, the manufacturing method of the plastic substrate according to the present invention is coated with an acrylate-based resin on one or both sides of the transparent plastic base film before the step of forming the inorganic thin film in order to secure the surface roughness of the plastic substrate and improve the adhesion to the inorganic thin film It is preferred to further comprise the step of.

Table 1 shows the chemical resistance results for alkali, ketone, alcohol of plastic substrates and glass of PET, PC, PES and PI. As shown in Table 1, the plastic substrate is inferior in chemical resistance to glass. Therefore, it is desirable to form an additional coating layer on the outermost layer of the substrate in order to improve the chemical resistance of the plastic substrate.

The plasma chemical vapor deposition method according to the present invention is not particularly limited, but in consideration of the object of the present invention, it is preferable to use the electron cyclotron resonance plasma chemical vapor deposition method.

Hereinafter, an embodiment according to the present invention will be described with reference to the accompanying drawings.

4 and 5 illustrate a structure in which a thin film is formed on one side and both sides of a plastic film substrate manufactured in the present invention. 11 (21) represents a protective layer, 12 (22) represents a gas barrier layer, 13 (23) represents an intermediate layer, and 14 (24) represents a plastic base film. On the plastic base film 14, a protective layer 11 made of an acrylate-based photocurable coating agent was formed on the end face to secure solvent resistance and scratch resistance. In addition, protective layers 11 and 21 are formed outside the gas barrier layers 12 and 22. The intermediate layers 13 and 23 were formed to improve the adhesive force between the gas barrier layers 12 and 22 and the plastic base films 14 and 24. This improved adhesion without using a silane coupling agent by using a silicone acrylate-based coating agent that can improve the interfacial affinity between the gas barrier layers 12 and 22, which are inorganic materials, and the base films 14, 24, which are organic materials. In the film forming conditions of the gas barrier layers 12 and 22, multilayer film quality was deposited in a direction in which the refractive index gradually decreased by adjusting the flow rate of nitrogen without changing the vacuum degree of the reaction system. As a result, not only the gas barrier characteristics but also the light transmittance were obtained.

Example 1

Plastic substrate films (PET, PC, PES, COC, Par) having a thickness of 200 μm were annealed in a convection oven at 150 ° C. to 180 ° C. for 1 day. One side of the film was coated with silicone acrylate using an automatic coater and cured with 200mJ ultraviolet (UV). The film was mounted in a vacuum chamber and evacuated to lower the pressure in the chamber to 5 × 10 ⁻⁶ torr. Deposition was carried out for 1 minute using 200W RF plasma at 20 ° C. and 5 × 10 ⁻¹ torr while introducing 50 sccm of oxygen gas, 15 sccm of argon gas, and hexamethyldisiloxane (HMDSO) at a rate of 2.44 g / hr. Nitrogen was added at 25 sccm, 50 sccm, and 75 sccm, and vapor deposition was performed for 1 minute. After stopping the gas injection, nitrogen was blown into the chamber to raise the pressure to atmospheric state, and the film was taken out, and acrylate-based hard coating was performed on both sides of the film by using an automatic coating machine. The schematic diagram of the produced board | substrate is shown in FIG.

Example 2

The experiment was conducted in the same manner as in Example 1, and the deposition was carried out on both sides of the film. 5 is a schematic view of the substrate produced through this.

Comparative Example 1

A 200 μm thick polyethersullon (PES) film was annealed in a 150-180 ° C. convection oven for 1 day. Without coating the surface of the film, the film was mounted and evacuated in a vacuum chamber to lower the pressure in the chamber to 5 × 10 ⁻⁶ torr. 0 sccm of oxygen gas, 115 sccm of argon gas, and hexamethyldisiloxane (HMDSO) were added at a rate of 2.44 g / hr, and deposited at 20 ° C. and 5 × 10 ⁻¹ torr using 200 W RF plasma for 1 minute. Here, 100 sccm of oxygen, 15 sccm of argon, and HMDSO were added at a rate of 2.44 g / hr, and deposited for 1 minute at 200 W of plasma power. HMDSO was added again at a rate of 1.22 g / hr, and deposition was attempted for 1 minute at 250 W of plasma power. After stopping the gas input, nitrogen was blown into the chamber to raise the pressure to atmospheric state and the film was taken out.

Comparative Example 2

After coating the PES surface in the same manner as in Example 1, the film was mounted in the vacuum chamber and evacuated to lower the pressure in the chamber to 5 × 10 ⁻⁶ torr. Oxygen gas 0 sccm, argon gas 115sccm, hexamethyldisiloxane (HMDSO) at a rate of 2.44 g / hr, was deposited for 1 minute using a 200W RF plasma at 20 ℃, 5x10 ^-1 torr. It was deposited at a plasma power of 200 W for 1 minute while charging at a rate of 100 sccm of oxygen, 15 sccm of argon, and 2.44 g / hr of HMDSO. HMDSO was added again at a rate of 1.22 g / hr and deposited for 1 minute at 250 W of plasma power. After stopping the gas injection, nitrogen was blown into the chamber to raise the pressure to the atmospheric state, and the film was taken out, and acrylate-based hard coating was carried out using an automatic coating machine on both sides of the film.

Experimental Example

The plastic substrates prepared in Examples 1 and 2 and Comparative Examples 1 and 2 were transparent and no bending phenomenon was found. The effect of increasing the nitrogen flow rate on the physical properties of the thin film deposited on the plastic substrate was investigated as follows.

1. Change of Element Content in Thin Films

In order to confirm the effect of increasing the nitrogen flow rate on the oxygen and carbon content in the thin film, the plastic substrates prepared in Examples and Comparative Examples were measured by X-ray photoelectron resonance (XPS). The measurement results are summarized in Table 2 below.

As can be seen from the table, it can be seen that the content of oxygen and carbon in the thin film is changed by increasing the nitrogen flow rate.

2. Change of refractive index of thin film

In order to investigate the effect of the increase in nitrogen flow rate on the refractive index of the thin film deposited on the plastic substrate, the refractive index of the plastic substrates prepared in Examples and Comparative Examples was measured using a spectroscopic ellipsometer. The measurement results are summarized in Table 3.

As the refractive index of the thin film gradually decreased with increasing nitrogen flow rate, it can be seen that a thin film having a different film quality was formed. 3 and 4 show schematic diagrams of substrates prepared on this basis.

3. Gas barrier properties of thin film

Gas barrier properties were measured using MOCON equipment (ASTM F1249), summarized in Table 4.

* Water vapor transmission rate of PES: 60 gm / ㎡?

The water vapor transmission rate of the plastic substrate produced by the comparative example is 13 times for single-sided deposition and 40 times for double-sided deposition, compared to the plastic substrate of the embodiment, and thus the plastic substrate produced by the present invention has high gas barrier properties. You can see that you have.

4. Light transmittance of thin film

In order to measure the light transmittance of the plastic substrate, the light transmittance was measured at 550 nm using a JASCO V560 (UV-visible meter), and the results are shown in FIGS. 6 and 7. In summary, the light transmittance of PES, which is a plastic substrate, was 88%, the result obtained in Example 1 was 93%, the result obtained in Example 2 was 95%, the result obtained in Comparative Example 1 was 90%, and Comparative Example The result by 2 was 91% (measured at 550 nm). Accordingly, it can be seen that the plastic substrate of the example increased the light transmittance by 3% compared to the plastic substrate of the comparative example in the case of single-sided deposition, and increased the light transmittance by 4% in the case of double-sided deposition.

In the present invention, by forming an intermediate layer having improved adhesion to the plastic substrate film, and by effectively changing the refractive index of the thin film without changing various process variables through the change of nitrogen flow rate during deposition, to form a high-density thin film having different refractive index In this way, gas barrier properties and light transmittance are improved.

Claims (11)

A method of forming an inorganic thin film by depositing a composite inorganic precursor and a reaction gas containing a hydrocarbon on one or both sides of the transparent plastic substrate film by plasma chemical vapor deposition, Wherein said step is performed under conditions of increasing the nitrogen flow rate in the plasma chamber. The method of claim 1, wherein the increased nitrogen flow is at most 500 sccm and the nitrogen flow is increased continuously or discontinuously. The method of claim 1, wherein the rate of increase of the nitrogen flow rate is 20 to 30 sccm / min. The method of claim 1, wherein the composite inorganic precursor is hexamethyldisiloxane, hexamethyldisilazane, tetraethoxysilane, tetramethoxysilane, methoxytrimethylsilane, tetramethylsilane, triphenylsilane, tetrachlorosilane, trichloro Consisting of methylsilane, trimethylchlorosilane, dimethyldichlorosilane, dimethylchlorosilane, pentakisdimethylamino tantalum, pentaethoxy tantalum, titanium isopropoxide, titanium butoxide, zirconium tetrachloride and zirconium tetra-tert-butoxide At least one member selected from the group. The method of claim 1, wherein the reaction gas comprises oxygen, nitrous oxide, or ammonia. The method of claim 1, wherein the plastic base film is made of polyethylene terephthalate, polyether sulfone, polycarbonate, polyimide, polyarylate, cyclic olefin copolymer, epoxy resin or unsaturated ester resin Way. The method of claim 1, wherein the plasma chemical vapor deposition method uses electron cyclotron resonant plasma chemical vapor deposition. The method of claim 1, wherein the inorganic thin film is a metal oxide, a metal oxide, or a metal nitride including one or two or more metals selected from the group consisting of Si, Ta, Ti, and Zr. . The method of claim 1, further comprising pretreating one or both surfaces of the transparent plastic base film with oxygen, argon, and nitrogen plasma before forming the inorganic thin film. The method of claim 1, further comprising coating an acrylate-based resin on one or both surfaces of the transparent plastic base film before forming the inorganic thin film. The plastic substrate manufactured by the method of any one of Claims 1-10.

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