JPH1126155A - Protection film for electroluminescent element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a protection film for an electroluminescent element with less performance drop caused by heat or stress, high gas barrier capability, and high transparency by forming a diamond-like carbon film having the specified hydrogen content and oxygen content on at least one side of a transparent film. SOLUTION: A diamond-like carbon film having a hydrogen content of 50 atomic percent or less, preferably 45 atomic percent or less, more preferably 40 atomic percent or less and an oxygen content of 2-20 atomic percent, preferably 2-15 atomic percent, more preferably 2-10 atomic percent is formed on at least one side of a transparent film. As the transparent film, a film such as polyethylene terephthalate having not so high glass transition temperature, a light transmission of 85% or more, smooth surface, and a thickness of 0.01-1 mm is preferable. The diamond-like carbon film is prepared by using a raw material gas containing methane, carbon monoxide, or the like and by plasma CVD, and preferable to have a thickness of about 0.5 μm or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transparent film used for protecting electroluminescence.

[0002]

2. Description of the Related Art Heretofore, in order to prevent deterioration of foods, medicines and the like, they have been packaged with a gas barrier film. In the field of electronics,
The electroluminescent element is protected by a gas barrier film to extend its life. It is known that the life of an electroluminescent light emitting device in which an electroluminescent element is covered with a gas barrier film depends on the oxygen permeability and moisture permeability of the gas barrier film. It is important to reduce this.

[0003] As a gas barrier film, a film in which an inorganic compound is provided on a polyethylene terephthalate film, a polypropylene film, or a polyamide film is known. As an example, a film obtained by depositing silicon oxide or aluminum oxide on a film surface (Japanese Patent Publication No. 53-1)
2953, JP-B-62-49856). However, when various articles are packaged and covered with the gas barrier film, heat sealing is usually employed. At this time, naturally, heat and stress act on the film. When these gas barrier films are used, an elongation phenomenon occurs in the film due to the heat and stress, and the inorganic compound layer cannot follow this elongation phenomenon, a minute crack is generated, and the gas barrier property is reduced. There was a problem.

For this reason, Japanese Patent Application Laid-Open No. Hei 4-139233 discloses a gas barrier film in which an inorganic compound layer having a gas barrier property is provided on at least one side of a transparent film. Certain films had to be used. Japanese Patent Application Laid-Open No. Hei 6-344495 discloses a gas barrier film used for protecting an electroluminescence element, but has poor transparency.

[0005]

According to the present invention, even when a film having a high glass transition temperature is not used as a base material, the performance is not significantly reduced by heat or stress acting during use, and the gas barrier property can be sufficiently exhibited. It is intended to provide a film having excellent properties.

[0006]

In order to solve the above-mentioned problems of the prior art, the present inventor has conducted various studies. As a result, even when a general-purpose film is used, the performance is reduced even when heat or stress is applied. The inventors have found that a gas barrier film which does not cause any problem can be obtained, and have completed the present invention. That is, the gas barrier film according to the present invention is characterized in that a diamond-like carbon film having a hydrogen concentration of 50 atomic% or less and an oxygen concentration of 2 to 20 atomic% is formed on at least one surface of the transparent film. Is what you do.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The diamond-like carbon film referred to in the present invention is an amorphous diamond-like carbon,
Contains diamond, graphite, and polymer components. The properties of the diamond-like carbon film differ depending on the mixing ratio of these components. Even a diamond-like carbon film having high hardness does not always function as a gas barrier layer for water vapor, oxygen, and the like.

Conventionally, the film quality of a diamond-like carbon film has been considered using its hydrogen concentration as an index. That is, the lower the hydrogen concentration, the more the film exhibits the properties of diamond,
On the other hand, when the hydrogen concentration increases, the hardness of the film decreases due to the properties of graphite or polymer. However, it is considered that the gas barrier properties of the diamond-like carbon film do not always correspond to the hardness of the film. Further, since the gas barrier property is considered to be determined by the concentration of the site where the atoms constituting the film are disconnected, it has been considered that the reduction of the hydrogen concentration contributes to the improvement of the gas barrier property.

The present inventor has studied the reduction of the hydrogen atom content in the film in order to improve the gas barrier properties of the film, but the transparency of the obtained film was not always preferable. Therefore, when a method for increasing the transparency of the film was examined without increasing the hydrogen concentration in the film, surprisingly, it was surprising that oxygen atoms, which had conventionally been considered to be a cause of deteriorating gas barrier properties, were changed. It has been found that the effect of increasing the transparency can be obtained without appropriately deteriorating the gas barrier properties of the film by appropriately adding it in the film. That is, the concentration of hydrogen contained in the diamond-like carbon film acting as a barrier layer for water vapor or oxygen of the present invention is 5%.
It is 0 atomic% or less, preferably 45 atomic% or less, more preferably 40 atomic% or less. Further, the oxygen concentration is 2 to 20 at%, preferably 2 to 15 at%, and more preferably 2 to 10 at%.

In order to form the diamond-like carbon film, a source gas containing carbon and hydrogen is used. Examples of the raw material gas containing carbon and hydrogen include alkane-based gases such as methane, ethane, propane, butane, pentane, and hexane; ethylene, propylene, butene,
Alkene-based gases such as pentene, alkane-based gases such as pentadiene and butadiene; alkyne-based gases such as acetylene and methylacetylene; benzene, toluene,
Aromatic hydrocarbon gases such as xylene, indene, naphthalene, and phenanthrene; cycloalkene gases such as cyclopropane and cyclohexane; alcohol gases such as methanol and ethanol; ketone gases such as acetone and methyl ethyl ketone; And aldehyde gases such as ethanal. The above gases may be used alone or in combination of two or more.

The raw material gas containing carbon and hydrogen includes a mixture of the raw material gas and hydrogen gas; a gas composed of only carbon and oxygen such as carbon monoxide gas and carbon dioxide gas. A mixture of the above gases; a mixture of hydrogen gas and a gas composed only of carbon and oxygen, such as carbon monoxide gas and carbon dioxide gas; and a gas composed of only carbon and oxygen, such as carbon monoxide gas and carbon dioxide gas, and oxygen Examples thereof include a mixture with gas and water vapor. Further, as the raw material gas containing carbon and hydrogen, a mixed gas of the above raw material gas and a rare gas may be used. For example, helium,
Examples thereof include argon, neon, and xenon, and these may be used alone or in combination of two or more.

The mixing amount of the hydrogen gas and the rare gas in the mixed gas varies depending on the type of the apparatus used, the type of the mixed gas, the film forming pressure, and the like. Specifically, the concentration of hydrogen contained in the formed diamond-like carbon film is adjusted to be 50 atomic%, preferably 45 atomic% or less, more preferably 40 atomic% or less. The concentration is adjusted so as to be 2 to 20%, preferably 2 to 15% by atom, and more preferably 2 to 10% by atom. Further, as a carbon source, solids of carbon isotopes such as graphite and diamond can be used, and they are used by being installed in a plasma of a hydrogen gas or a rare gas atmosphere.

Means for exciting the raw material gas by plasma include, for example, a method of applying a direct current to perform plasma decomposition; a method of applying a high frequency to perform plasma decomposition; a method of performing plasma decomposition by microwave discharge; A method of plasma decomposition; a method of thermal decomposition by heating with a hot filament, and the like. Among them, the method of applying DC plasma is not preferable because the plasma is not generated when the substrate is a plastic film which is an insulator. When the hot filament method is used, the filament is 50
Since the temperature must be as high as 0 ° C. or more, it may not be preferable in consideration of the heat resistance of the substrate. A microwave plasma method or a method of decomposing plasma by electron cyclotron resonance is preferable because a film formation rate is high and a film formation temperature is low. In the case of forming a film on a large-area resin film, it is preferable to use a high-frequency plasma method. In addition, as a method for forming the diamond-like carbon film, there are physical vapor deposition methods such as ion beam sputtering and ion plating, and these methods may be employed.

The thickness of the diamond-like carbon film is determined as necessary. When the thickness is large, the adhesion to the substrate film is deteriorated, the coating is deformed by film stress, and the transparency is deteriorated. Therefore, the thickness is preferably 0.5 μm or less, more preferably 0.1 μm or less, and still more preferably 0.05 μm or less.

Examples of the above plastics film substrate include polyester films such as polyethylene terephthalate; polyolefin films such as polyethylene, polypropylene and polybutene; polystyrene films; polyamide films;
Polyacrylonitrile film; polyetherimide;
Polyether sulfone; polysulfone; polyimide and the like can be used.

The light transmittance of the substrate film is preferably at least 85%, more preferably at least 88%.
The plastic film substrate may be a stretched film or an unstretched film, and has a thickness of 0.01 to 1 m.
m is preferred. The smoothness of the film surface is preferably as high as possible. This is because if the surface smoothness is low, gas barrier properties may be reduced. Specifically, Rmax (the maximum value of the difference between the peak and the valley) representing the surface roughness is 0.10.
μm or less, more preferably 0.05 μm or less. Ra representing the average roughness is 10 nm or less, preferably 5 nm or less.

In order to enhance the adhesiveness of the surface of the plastic film base material, if necessary, a cleaning treatment such as cleaning for degreasing and dehydrating the base material surface, and applying He gas to the base material surface in a vacuum container. A known process such as a plasma process using an inert gas such as an inert gas or an active gas such as an oxygen gas may be performed.

<Method for Producing Diamond-like Carbon Film> The apparatus used in the present invention will be described below with reference to the drawings. FIG. 1 is a schematic view showing one example of an apparatus for producing a diamond-like carbon film of the present invention. In FIG. 1, 1 is a vacuum container, 2 is a high-frequency electrode, and 3 is a base film attached to a Si wafer. 4 is a matching device, 5 is a high-frequency power supply, 6 is a thermocouple, 7 is a cooling plate, and 8 is a gas introduction pipe.

The temperature of the substrate film is controlled by a method of circulating a liquid or gas, infrared rays, electric heating, or the like. It is preferable that the temperature is maintained at least below the glass transition point of the substrate film. A liquid circulation system having a large heat capacity is preferred. At this time, the liquid to be circulated may be a liquid heated or cooled to a predetermined temperature, and the liquid to be circulated may be water, ethylene glycol (antifreeze), alcohols. Liquid nitrogen, liquid helium and the like are preferably used.

It is preferable to apply a DC bias to the substrate in order to widen the range of the composition of the usable source gas or to improve the quality of the film.
100V is preferable, and more preferably -400 to 10V
It is.

Next, a film forming operation will be described. First, after a plastic film substrate attached to a Si wafer is placed on the cooling plate 7 in the vacuum vessel 1, the inside of the vacuum vessel is made high vacuum. The degree of vacuum at this time is set to 10 ⁻⁴ Torr in order to eliminate the influence on the film formation due to the remaining impurity gas.
The following is preferred. Next, a raw material gas is introduced from a gas introduction pipe and maintained at a predetermined pressure. The pressure at this time is 1 × 10 ^-3
-10 Torr is preferred.

The gas barrier film according to the present invention may be a laminated type in which a predetermined number of the films are integrated by a method such as bonding with an adhesive or the like or heat fusion. In addition, in order to improve the heat sealing property at the time of use,
A hot melt adhesive can be provided. This adhesive layer is preferably provided on the diamond-like carbon film layer, but may be provided on a transparent film. As the hot melt adhesive, a general-purpose adhesive can be used, and an adhesive containing ethylene-vinyl acetate copolymer, polyethylene, polypropylene or the like as a main component can be used.

[0023]

【Example】

(Example 1) A polyethylene terephthalate film ("Lumirror highly transparent type" manufactured by Toray Industries, Inc.) having a thickness of 50 μm was attached to a Si wafer, and then placed on a cooling plate 7 in a vacuum vessel 1 shown in FIG. 1 × 10 inside the vacuum vessel
^The pressure was reduced to ^-5 Torr. Next, gas is introduced from the introduction pipe 8. Set C ₂ H ₂ to 50 sccm. After the pressure in the reaction chamber was set to 10 × 10 ⁻³ Torr, the frequency was 13.56.
The film was formed for 2 minutes by applying a high frequency power of 150 MHz at 150 MHz.

The thickness of the film determined by observation with a transmission electron microscope was about 0.1 μm. As a result of evaluating the obtained film by Raman spectroscopy, it was confirmed that the film was a diamond-like carbon film. When the composition of the film is determined using SIMS, the diamond-like carbon film contains 43 atomic% of hydrogen,
Oxygen was contained at 5 atomic%.

Example 2 A film was formed on a 50 μm thick polyethylene terephthalate film (“Lumirror” manufactured by Toray Industries, Inc.) in the same manner as in Example 1.

Example 3 A polyethylene terephthalate film having a thickness of 12 μm (“OPE” manufactured by Tocelo Co., Ltd.)
T)), a film was formed in the same manner as in Example 1.

Comparative Example 1 A film was formed on a 50 μm thick polyethylene terephthalate film (“Lumirror highly transparent type” manufactured by Toray Industries, Inc.) in the same manner as in Example 1.

Comparative Example 2 A film was formed on a polyethylene terephthalate film ("Lumirror" manufactured by Toray Industries, Inc.) having a thickness of 50 μm in the same manner as in Example 1.

Comparative Example 3 A polyethylene terephthalate film having a thickness of 12 μm (“OPE” manufactured by Tosero Corporation)
T)), a film was formed in the same manner as in Example 1.

<Evaluation of diamond-like carbon film> The diamond-like carbon film formed on the substrate in the above Examples and Comparative Examples was evaluated for a film and a substrate film deposited by the following evaluation method. It is shown in Table 1. (1) Moisture permeability Using a gas permeability measuring device manufactured by Mocon, 40
The measurement was performed under the conditions of ° C and 90% relative humidity. (2) Oxygen permeability Using a gas permeability measuring device manufactured by Yanaco Co., Ltd., the measurement was performed in an oxygen atmosphere at 23 ° C. (3) Light transmittance, haze (HAZE), b value (yellow,
(Ratio of blue) Integrating sphere haze meter (ND-1001D manufactured by Nippon Denshoku)
It measured using.

[0031]

[Table 1]

<Evaluation of Flex Resistance> (Example 4) A film produced under the same conditions as in the example was bent 100 times using a Gelboflex tester, and the moisture permeability, oxygen and other excess were measured.

(Comparative Example 4) A 12 μm-thick polyethylene terephthalate film (“Lumirror” manufactured by Toray Industries, Inc.) in a known vacuum evaporation apparatus using SiO as an evaporation source under an oxygen atmosphere at a pressure of 6 × 10 −5 Torr. A film of silicon oxide having a thickness of about 0.1 μm was formed on the surface of the base material. It was bent 100 times using a gelbo flex tester, and the moisture permeability and oxygen permeability before and after that were measured.

[0034]

[Table 2]

<Trial Production of EL Element> (Example 5) A polyester film having a glass transition temperature of 70 ° C., a transmittance of light having a wavelength of 550 nm of 88%, and a thickness of 50 μm (one side of “Lumirror” manufactured by Toray Industries, Inc. The film (DLC) has a thickness of 10 by plasma CVD.
The film was formed to have a thickness of 0 nm. Then, the two vapor-deposited films were overlapped in the order of film-DLC-film-DLC, and bonded and integrated with a transparent adhesive.
Next, a hot melt adhesive composed of an ethylene-vinyl acetate copolymer (vinyl acetate content: 8% by weight) was formed on the DLC layer by a melt extrusion method to obtain a laminated gas barrier film.

On the other hand, a transparent electrode in which a transparent electrode layer made of a mixture of indium oxide and tin oxide is provided on one side of a polyethylene terephthalate film, and a luminescent material obtained by dispersing zinc sulfide-based fluorescent powder in cyanoethylated cellulose. An electroluminescent device is prepared in which an insulating layer in which a layer and a titanium oxide powder are dispersed in cyanoethylated cellulose and a transparent electrode made of aluminum are laminated in this order. Then, the gas barrier film of the above-mentioned lamination type is superimposed on both sides of this element so that the hot melt adhesive layer is on the inside, and the temperature is 130 ° C. and the roll linear pressure is 5 kg.
By applying heat and pressure using a roll under the conditions of / cm and a tension of 3 kgf, an electroluminescence device having a structure covered and protected by a gas barrier film was obtained. When this electroluminescent device was continuously operated by a power supply of 100 V and 400 Hz, and its luminance half-life was measured,
2000 hours.

Comparative Example 5 A polyethylene terephthalate film ("Lumirror" manufactured by Toray Industries, Inc.) having a glass transition temperature of 70 ° C., a light transmittance of 550 nm at a wavelength of 88%, and a thickness of 50 μm was used as a substrate of a gas barrier film. Was used as a gas barrier layer in the same manner as in Example 4 to obtain a laminated gas barrier film and an electroluminescence device. When this electroluminescent device was continuously operated in the same manner as in the example, a partial blackening phenomenon of the light emitting surface was caused by the permeated moisture in about 200 hours, and the luminance half-life was as short as 800 hours.

[0038]

The present invention is configured as described above,
Even when a general-purpose transparent film is used without using a special film as the base material, the performance is less reduced by heat and stress acting during use, and the gas barrier properties can be sufficiently exhibited.

[0039]

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a film forming apparatus for producing a laminated film according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Vacuum container 2 High frequency electrode 3 Base film stuck on Si wafer 4 Matching device 5 High frequency power supply 6 Thermocouple 7 Cooling plate 8 Gas introduction pipe

Claims (1)

[Claims] At least one surface of a transparent film has a hydrogen concentration of 50 atomic% or less and an oxygen concentration of 2 to 20%.
A protective film for an electroluminescent device, wherein a diamond-like carbon film having an atomic percentage of at least one is formed.