JP2007307784A - Gas barrier film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas barrier film having both of excellent steam barrier properties and high transparency because it is known that an organic EL element is extremely weak against oxygen or moisture and the deterioration of the organic EL element caused by the penetration of oxygen and steam into the organic EL element is brought about if the organic EL element is allowed to stand in a state exposed to the atmosphere while it is indispensable to apply barrier properties to a plastic base material in order to realize the flexible organic EL element because the plastic base material is inferior to water and oxygen barrier properties. <P>SOLUTION: The gas barrier film is obtained by providing a silicon oxide (SiOx) film 2 formed using a plasma CVD method using a silane compound as a start raw material on one side or both side of the plastic base material 1. The silicon oxide film 2 is characterized in that an x-value is within a range of 1.9-2.1, a refractive index is within a range of 1.45-1.48 and the ratio of a hydrogen atom in the film is 30% or below. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a gas barrier film effective for imparting flexibility to a flat panel display represented by a liquid crystal element (LCD), an electroluminescence element (EL) and the like.

  Organic EL displays, which are self-luminous materials, are attracting attention as flat panel displays that replace cathode ray tubes and liquid crystal displays because of their many advantages such as low power consumption, high response speed, and high viewing angle. In general, an organic EL element is formed by laminating an anode, an organic light emitting layer, and a cathode on a transparent substrate, and light is emitted from the organic light emitting layer by applying a voltage between both electrodes. In addition, organic EL can be made thinner and lighter due to its structure, and it is highly expected to be applied to flexible displays.

  However, organic EL elements are known to be very sensitive to oxygen and moisture. If such organic EL elements are left exposed to the atmosphere, they will deteriorate due to the entry of oxygen and water vapor into the organic EL elements. Is known to be caused. In particular, alkali metals or alkaline earth metals with a low work function used for the cathode layer are easily oxidized by moisture, which inhibits the injection of electrons and generates non-light-emitting regions called dark spots. Expand with. Therefore, at present, the organic EL element is formed on glass and sealed with a desiccant and a sealing tube.

Generally, plastic substrates have poor water and oxygen barrier properties, and the water vapor barrier property necessary to protect the cathode layer is said to be 1 × 10 ^-6 g / m ² / day. In order to achieve this, it is indispensable to impart barrier properties to the plastic substrate (see Patent Document 1 and Non-Patent Document 1). The barrier layer is mainly made of highly transparent oxides such as silicon and aluminum, and nitrides, and is known to be formed by sputtering, ion plating, vacuum deposition, CVD, or the like. It has been. Furthermore, heat resistance, chemical resistance, alkali resistance, acid resistance, and the like in various processes that occur during display fabrication are required, and it is also required to maintain high barrier properties in various environments.

Silicon oxide films have been studied as various barrier films for a long time and have been put to practical use in the food packaging field (see Patent Document 2). However, if an attempt is made to obtain a barrier property, it is colored, and the barrier property is not sufficient. In recent years, PECVD has also been used as a method for producing high-quality silicon oxide films. To obtain high-quality films, special gas-designated silane (SiH ₄ ) must be used, or the deposition temperature can be increased. When it was hot, it was difficult to apply to plastic substrates. A silicon oxide film by PECVD method using an improved organosilane compound has been studied, but none has sufficient physical properties as a barrier substrate for organic EL (see Non-Patent Document 2). .
JP 2001-118674 A Japanese Patent Application Laid-Open No. 7-164591 PIONEER R & D Vol. 11 No.3 “Development of organic film display” "Novel Transparent Gas Barrier Film Prepared by PECVD Method", 43rd Annual Technical Conference Proceedings, Society of Vacuum Coater, 1, (2000)

  The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a gas barrier film having excellent water vapor barrier properties and high transparency.

  The present invention has been made in view of the above problems, and the present invention provides a gas barrier film having a silicon oxide (SiOx) film formed by a plasma CVD method using a silane compound as a starting material on one or both sides of a plastic substrate. A gas barrier film having a silicon oxide (SiOx) film formed by a plasma CVD method using a silane compound as a starting material on one or both sides of a plastic substrate, wherein the silicon oxide film has a value of x Is in the range of 1.9-2.1, the refractive index is in the range of 1.45-1.48, and the ratio of hydrogen atoms in the film is 30% or less.

First, according to the present invention, the composition of the silicon oxide film formed as the gas barrier film is made close to the stoichiometric SiO ₂ and the refractive index is regulated to 1.45-1.48. By defining the refractive index to 1.45-1.48, the composition and density can be controlled. Furthermore, it is considered that a SiOx film having few defects can be obtained by setting the ratio of hydrogen atoms in the film to 30% or less, and higher barrier properties can be expected.
Therefore, according to the present invention, it is possible to provide a gas barrier film having excellent water vapor barrier properties and high transparency.

The present invention will be described in detail below.
FIG. 1 is a cross-sectional view illustrating a gas barrier film of the present invention. The base material (1) in FIG. 1 is a plastic base material made of a transparent plastic material, and a silicon oxide film (2) is formed on the base material by a plasma CVD method. Hereafter, a plastic base material and a silicon oxide film are demonstrated in order.

[Plastic substrate]
The transparent plastic substrate used in the present invention is preferably a transparent film in order to make use of the transparency of the barrier layer. Examples include polyester films such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polycarbonate films (PC), polyethersulfone (PES), polyarylate films, polyolefin films such as polyethylene and polypropylene, and cyclic cycloolefins. A cycloolefin film, a polystyrene film, a polyamide film, a polyvinyl chloride film, a polyacrylonitrile film, a polyimide film, or the like is used. Either a stretched film or an unstretched film, and a material having mechanical strength and dimensional stability are preferable. These are processed into a film and used. There is no problem even if the film is arbitrarily stretched in the biaxial direction. In addition, various well-known additives and stabilizers such as an antistatic agent, an anti-ultraviolet agent, a plasticizer, and a lubricant may be used on the surface of the base material, in order to improve the adhesion to the thin film. In addition, a primer layer may be provided, or a corona treatment, a low temperature plasma treatment, or an ion bombardment treatment may be performed as a pretreatment, and a chemical treatment or a solvent treatment may be further performed.

[Silicon oxide film]
The gas barrier film of the present invention is a silicon oxide film (SiOx) formed by a plasma CVD method using a silane compound as a starting material, and can be formed on one or both surfaces of the substrate. . Further, it is preferable to use a winding type vacuum film forming apparatus capable of performing continuous vapor deposition by taking up the characteristics of the plastic substrate.

Next, an example of a winding type vacuum film forming machine for forming this silicon oxide film will be shown.
FIG. 2 is a schematic diagram thereof. The vacuum film forming apparatus (3) for producing the transparent gas barrier film includes a web-shaped plastic substrate unwinding / winding chamber (4) that can be wound with a constant tension such as a torque motor. A winding shaft (6) having a means, and a winding shaft (6) enabling unwinding of the web-shaped plastic film substrate (8) while applying a constant back tension by a torque control means such as a powder clutch, A plurality of idle rollers (11, 12) for regulating the travel of the plastic substrate, tension rolls (13, 14) equipped with a tension detector for appropriately feeding back, temperature for monitoring the temperature of the film surface The film forming chamber (5) includes a sensor (15, 16), and a film forming drum (17) with temperature control for controlling the temperature of the film surface during film formation and forming a film on the surface. ), This is a vacuum film-forming apparatus in which a film-forming part consisting of an electrode (18) for plasma CVD having a shower head for introducing a process gas or a raw material gas is arranged. Reference numeral 9 denotes a web-shaped plastic film original, and reference numeral 10 denotes a web-shaped film. An example of the take-up vacuum film forming apparatus is shown as an example this time, but there is no problem at all with other batch type film forming apparatuses. As a plasma generation method, a low temperature plasma generator such as direct current (DC) plasma, low frequency plasma, high frequency (RF) plasma, pulse wave plasma, tripolar structure plasma, microwave plasma, or the like is used.

A silicon oxide film formed by a plasma CVD method is formed by using a material obtained by adding a silane compound and oxygen gas, and optionally adding an inert gas as a raw material. Examples of silane compounds include silane (SiH ₄ ), dichlorosilane, tetrachlorosilane, tetraethoxysilane (TEOS), tetramethoxysilane (TMOS), tetramethylsilane (TMS), hexamethyldisilane (HMDS), hexamethyldisilane. A relatively low molecular weight silane compound such as siloxane (HMDSO), tetramethyldisiloxane, or methyltrimethoxysilane may be selected, and one or more of these silane compounds may be selected. However, silane compounds such as silane, dichlorosilane, and tetrachlorosilane are both toxic and explosive and difficult to handle. In view of safety and vapor pressure among these silane compounds, organic silicon compounds such as TEOS, TMOS, TMS, HMDS, and HMDSO are preferable. For film formation, these organosilicon compounds are vaporized, mixed with oxygen gas, introduced into the film formation chamber (5) of the vacuum film formation apparatus, and the temperature-controlled film formation drum (17) and electrode (18 ) Plasma is generated, and a silicon oxide film is formed on the plastic substrate by plasma CVD. The properties of the silicon oxide film can be changed by various methods in the plasma CVD method. For example, various methods such as change of organosilicon compound and gas type, mixing ratio of organosilicon compound and oxygen gas, input power, and the like can be considered.

  The thickness of the silicon oxide film that is a barrier layer is not particularly limited, but if it is too thin, it is difficult to express the barrier property, and it is considered that 10 nm or more is necessary. A film thickness greater than this can be controlled in accordance with the required barrier performance as long as the transparency is not impaired. However, although a problem arises in terms of flexibility and economy, which results in a certain film thickness, the range of 50 to 500 nm is preferable if it is desired to obtain a barrier property suitable for organic EL. Also, the film thickness can be controlled by controlling the film formation time in the batch apparatus, but in the case of a winding type apparatus, it can be controlled by changing the line speed or the number of electrodes. It is also possible to increase the film thickness by reversing after film formation once.

The detailed composition of the obtained silicon oxide film and the analysis of the hydrogen concentration can be determined by Rutherford Backscattering Spectroscopy (RBS) and recoil detection method (ERDA method). These measurement methods are analysis to obtain the constituent elements and composition of the sample surface by irradiating the sample with well collimated high-speed He2 + and measuring the energy and intensity of He scattered back. Silicon and nitrogen can be quantified by RBS, and hydrogen can be quantified by ERDA.
The value of x of the silicon oxide film (SiOx) was defined as 1.9-2.1 because it was found that a composition close to the stoichiometric SiO ₂ was necessary for the barrier film. If it deviates, it will deviate from the stoichiometry, and excessive bonds will be generated, making it difficult to develop barrier properties. On the other hand, if it is less than 1.9, a silicon-excess film is formed, and the film may be colored. Further, it is considered that a SiOx film having few defects can be obtained by setting the obtained hydrogen concentration to 30% or less. When it is defined only by the value of x of SiOx, even if the ratio of silicon and oxygen approaches 2, it is difficult to specify the structure. That is, a structure containing hydrogen such as Si—H bond or SiO—H bond in the film is considered, and it is considered structurally a defect. Thus, by defining the amount of hydrogen present, it is possible to reduce these defects and to expect high barrier properties.

The refractive index of the silicon oxide film can be measured by ellipsometry. Measurement was performed using laser light having a wavelength of 633 nm. In addition, the measurement can be performed by measuring the transmitted light and reflected light of the obtained gas barrier film. The refractive index of the film can be defined by a refractive index in a range in which silicon oxide does not absorb. The refractive index of the silicon oxide film is mainly correlated with the density. For example, the refractive index of the SiO ₂ film in the stoichiometry obtained by the thermal CVD method is 1.465. It is known that if this value is larger than (1.465 <) a silicon-excess film, and if it is smaller (1.465>), an oxygen-excess or low-density film is obtained. In this silicon oxide film by plasma CVD method using silane compound with carbon in the molecule as the starting material, the refractive index is regulated to 1.45-1.48, the composition and density can be controlled, and the high barrier property. Can be maintained.

EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated, it is not limited to a following example.

[Example 1]
Using a biaxially stretched polyethylene terephthalate (PET) film with a thickness of 100μm as a base material, it is set in the unwinding part of the wind-up type plasma CVD film forming apparatus shown in Fig. 2 and evacuated with a vacuum pump to form a wind-up type plasma CVD film. The inside of the membrane device was depressurized to 5 × 10 ⁻⁵ torr. Next, a raw material gas mixed so that hexamethyldisiloxane (HMDSO): oxygen = 10: 100 is introduced from a shower head on each electrode surface of the film forming chamber, and the inside of the film forming chamber is 2 × 10 ⁻² torr. It was. Subsequently, a high frequency of 13.56 MHz was applied to each electrode at 0.5 kW to generate plasma. Subsequently, the PET film was run at 0.3 m / min for film formation. The thickness of the silicon oxide film obtained at that time was 100 nm. Thus, the gas barrier film 1 which is the object of the present invention was obtained.

[Example 2]
In Example 1, the high frequency power applied to each electrode is 1.0 kW, the HMDSO: oxygen ratio is 15: 100, and the line speed is adjusted so that the thickness of the silicon oxide film is 100 nm. The objective gas barrier film 2 was obtained.

[Comparative Example 1]
In Example 1, an HMDSO: oxygen ratio was set to 15: 100, and the line speed was adjusted so that the thickness of the silicon oxide film was 100 nm to obtain a film on which silicon oxide was formed.

[Comparative Example 2]
In Example 2, an HMDSO: oxygen ratio was set to 20: 100, and the line speed was adjusted so that the thickness of the silicon oxide film was 100 nm, thereby obtaining a film on which silicon oxide was formed.

  The composition ratio of the obtained silicon oxide film was determined by performing RBS and ERDA measurements on a film formed on a silicon substrate under the same conditions. The measurement conditions for RBS and ERDA were beam energy of 2300 eV, ion species He +, scattering angle of 170 °, sample current of 30 nA, and beam irradiation amount of 40 uC.

The gas barrier property of the obtained sample was measured using a water vapor transmission rate measuring device (PERMATRAN-W 3/33 manufactured by MOCON) under the conditions of 40 ° C. and 90% relative humidity. The results are shown in the table below. The barrier property of the PET film used for the substrate is 5.0 g / m ² / day. The results are shown in the table.

  As shown in Table 1, in Example 1-2, it can be seen that by controlling the film composition as described above, the barrier property is very high as compared with the base material. The gas barrier film obtained in this way shows barrier properties below the detection limit of the water vapor transmission rate measurement device (PERCON-W 3/33 manufactured by MOCON), and can form a barrier film that can withstand display applications. It is.

  The gas barrier film of the present invention is effective for a flat panel display represented by a liquid crystal element (LCD), an electroluminescence element (EL) and the like.

It is sectional drawing explaining the gas barrier film of this invention. It is a schematic explanatory drawing which shows the whole figure of the winding-type vacuum film-forming apparatus concerning this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Plastic base material, 2 ... Silicon oxide film, 3 ... Vacuum film-forming apparatus, 4 ... Unwinding and winding chamber, 5 ... Film-forming chamber, 6 ... Unwinding shaft, 7 ... Winding Take-up shaft, 8 ... plastic film substrate, 17 ... temperature-regulating film forming drum, 18 ... electrode.

Claims (5)

  A gas barrier film having a silicon oxide (SiOx) film formed by a plasma CVD method using a silane compound as a starting material on one or both surfaces of a plastic substrate, wherein the silicon oxide film has a value of x of 1.9-2.1 A gas barrier film having a refractive index in the range of 1.45-1.48 and a hydrogen atom ratio in the film of 30% or less.   The silicon oxide film is characterized in that the value of x is in the range of 1.98-2.01, the refractive index is in the range of 1.465-1.468, and the percentage of hydrogen atoms in the film is in the range of 15-20%. The gas barrier film according to claim 1.   The gas barrier film according to claim 2, wherein the silane compound is hexamethyldisiloxane.   The gas barrier film according to claim 3, wherein the silicon oxide film has a value of x of 1.98, a refractive index of 1.465, and a ratio of hydrogen atoms in the film of 20%. The gas barrier film according to claim 3, wherein the silicon oxide film has a value of x of 2.01, a refractive index of 1.468, and a ratio of hydrogen atoms in the film of 15%.

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