JP2002313559A - Charge injection type light emitting element and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a charge injection type light emitting element provided with a protective film of a long service life with a sufficient heat radiating property and a high shielding property to oxygen and moisture to an organic luminescent layer, a carrier transport layer and an electrode. SOLUTION: The surface exposed parts of the organic luminescent layer 11, carrier transport layer 10 and electrode 12 are irradiated with hydrogen ion in an energy range of less than 150 eV to provide a protective film formed of poly-paraxylene film for covering the surface exposed part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a protective film for a charge injection type light emitting device, and more particularly, to a charge injection type light emitting device having a protective film having low oxygen and moisture permeability and a method of manufacturing the same.

[0002]

2. Description of the Related Art With the spread of ITO films (transparent conductive films) used for liquid crystal or organic light emitting devices, demands for higher performance are increasing. It is strongly desired that the efficiency of charge injection as an electrode be increased.

Conventionally, to form an ITO film on a substrate or the like,
A film forming method by a dry process such as vacuum evaporation or sputtering is generally performed. However,
ITO obtained by vacuum evaporation or sputtering
Since the crystallinity of the ITO film depends on the substrate temperature and the film formation rate at the time of film formation, it is not possible to greatly improve the physical surface shape (surface roughness) and the electrical characteristics of the ITO film related to the crystal plane. It was difficult, and it was impossible to improve the function (charge injection property) as an electrode of an organic light emitting device or the like.

On the other hand, the electroluminescence phenomenon of organic materials is 1963.
And was observed in single crystals of anthracene by Pope et al. (J. Chem. Phys. 38 (196)
3) 2042), followed by Helfinch and Schneid in 1965
er) succeeded in observing a relatively strong injection-type EL (electroluminescence) by using a solution electrode system having a high injection efficiency (phys. Rev. Lett. 1).
4 (1965) 229).

Since then, US Pat. No. 3,172,862
No. 3,173,050, US Pat. No. 3,71
No. 0,167, J.M. Chem. Phys. 44 (196
6) 2902; Chem. Phys. 50 (196
9) 14364; Chem. Phys. 58 (19
73) 1542, or Chem. Phys. Let
t. 36 (1975) 345 etc.,
Studies have been conducted on the formation of an organic luminescent material with a conjugated organic host material and a conjugated organic activator having a fused benzene ring. Naphthalene, anthracene, phenanthrene, tetracene, pyrene, benzopyrene, chrysene, picene, carbazole, fluorene, biphenyl, terphenyl,
Triphenylene oxide, dihalobiphenyl, trans-stilbene, 1,4-diphenylbutadiene and the like are shown as examples of organic host materials, and anthracene, tetracene, pentacene and the like are mentioned as examples of activators. However, each of these organic luminescent substances is 1 μm
It existed as a single layer having a thickness exceeding the above, and a high electric field was required for light emission. For this reason, research on a thin film element by a vacuum deposition method has been advanced (for example, Thin Solid).
Films 94 (1982) 171, Polyme
r 24 (1983) 748, Jpn. J. Appl.
Phys. 25 (1986) L773).

Although thinning is effective in reducing the driving voltage, it has not led to obtaining a high-brightness element on a practical level.

However, in recent years Tang et al. (App
l. Phys. Lett. 51 (1987) 913 or U.S. Pat. No. 4,356,429), devising an EL device in which two extremely thin layers (a charge transport layer and a light emitting layer) are stacked by vacuum deposition between an anode and a cathode, and low driving is performed. High brightness was achieved with voltage. This type of stacked organic EL device has been actively studied thereafter, and is disclosed in, for example, JP-A-59-194393.
No. 4,539,507, British Patent 4,
720,432, JP-A-63-264692,
Appl. Phys. Lett. 55 (1989) 14
67, JP-A-3-163188 and the like.

Further, Jpn. J. Appl. Phys
s. 27 (1988) L269. L713 reports a three-layered EL device in which the functions of carrier transport and light emission are separated from each other. In selecting a dye of a light-emitting layer that determines a light emission color, restrictions on carrier transport performance are relaxed, and the degree of freedom of selection is reduced. It is also suggested that there is a possibility of improving the light emission by effectively confining holes and electrons (or excitons) in the central light emitting layer.

Although a vacuum evaporation method is generally used for producing a stacked organic EL device, it has been reported that a device having a considerably high brightness can be obtained by a casting method (for example, the 50th application). Proceedings of academic conference
006 (1989) and Proceedings of the 50th Annual Meeting of the Japan Society for Materials Science 1041 (1990)).

Furthermore, even a mixed single-layer EL device formed by a dip coating method from a solution in which polyvinyl carbazole as a hole transport compound, an oxadiazole derivative as an electron transport compound, and coumarin 6 as a luminous body has a considerably high luminous efficiency. Has been reported (eg,
Proceedings of the 38th Annual Conference of the Famous Relationships of the Lectures 1086 (19
91)).

[0011]

As described above, recent advances in organic EL devices have shown a remarkably wide range of possible applications.

[0012] However, the history of such research is still short, and research on the material and device development has not yet been sufficiently performed. At present, there is still a problem in terms of durability, such as light output with even higher luminance, a change with time due to long-term use, and deterioration due to an atmospheric gas containing oxygen or moisture.

That is, since the organic light emitting layer, the carrier transporting layer, and the electrode are easily deteriorated under the influence of moisture, oxygen, and other various molecules existing in the use environment, a protective film for completely shielding the organic light emitting layer, the carrier transporting layer and the electrode from the outside world is provided. Must be provided.

As the protective film, an inorganic coating such as an oxide, a carbide or a nitride, or a resin coating such as an epoxy resin can be considered. However, a sufficient shielding effect cannot be expected due to the presence of pinholes and the like. The heat storage effect resulting from the heat generation has deteriorated the element itself.

An object of the present invention is to solve such problems of the prior art, and an organic light emitting layer,
An object of the present invention is to provide a charge-injection light-emitting element provided with a long-life protective film that has high shielding properties against oxygen and moisture for a carrier transport layer and an electrode, has good heat dissipation properties, and has a long life.

[0016]

The configuration of the present invention which has been made to achieve the above object is as follows.

That is, the charge injection type light emitting device of the present invention is a charge injection type light emitting device having an organic light emitting layer and a carrier transport layer between a pair of electrodes at least one of which is transparent. A protective film made of a polyparaxylene film having a work function of 5.0 eV or more is provided on the layer and the exposed surface of the electrode.

Further, the method for manufacturing a charge injection type light emitting device of the present invention comprises the steps of:
In the method for manufacturing a charge injection type light emitting device having an organic light emitting layer and a carrier transport layer, hydrogen ions in an energy range of less than 150 eV are irradiated on the organic light emitting layer, the carrier transport layer, and the exposed surface of the electrode, A step of forming a polyparaxylene film covering the exposed portion of the surface.

A polyparaxylene film, particularly a p-xylylene polymer film or a chlorinated p-xylylene polymer film, has a very low gas and water vapor permeability and can obtain a uniform film with few pinholes. According to the method, the adhesion is extremely low and the strength of the film cannot be obtained. However, when a film is formed while irradiating hydrogen ions in a predetermined energy range as in the manufacturing method of the present invention, the work function representing the bonding state of the film increases, and a polyparaxylene film having a work function of 5.0 eV or more is formed. It can be formed, and the denseness, strength, and adhesiveness of the film are improved, and as a result, the life characteristics of the device are greatly improved.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION As a raw material of a polyparaxylene film used in the present invention, [2,2] paracyclophane,
Monomers such as [2,2 '] dichlorocyclophane and xylene resins such as parylene N (poly p-xylylene), parylene C (polymonochloro p-xylylene), and parylene D (polydichloro p-xylylene) are exemplified.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic view showing an example of an apparatus for producing a device by forming a polyparaxylene film according to the present invention as a protective film.

The above apparatus comprises a discharge tube 2 surrounded by a high-frequency coil 3 around a quartz tube 4 in a chamber 1 and an ITO tube.
The substrate holder 6 holds a substrate 13 on which a carrier transport layer 10, an organic light emitting layer 11, and an aluminum electrode 12 are sequentially formed on electrodes. Holder 6 is in electrical contact with aluminum electrode 12 and is connected to ammeter 7 and DC power supply 8. The high frequency coil 3 is connected to a high frequency power supply 5 and a capacitor 9.
Further, the discharge tube 2 is provided with a nozzle connected to a hydrogen gas supply device (not shown) via a mass flow controller (not shown).

The chamber 1 is connected to a vacuum exhaust device (not shown) so as to maintain a predetermined degree of vacuum.

The film formation of the carrier transport layer 10, the organic light emitting layer 11, and the aluminum electrode 12 on the glass substrate 13 having the ITO film can be performed in the above chamber.

That is, the glass substrate 13 having the ITO film is attached to the substrate holder 6 with the apparatus having the above-described configuration, and the inside of the chamber 1 is set to about 1.3 × 10 ^{−3 to} 1.3 × 10 ⁻⁴ Pa.
Evacuate to Then, an alternating current is applied to the board 14 containing the carrier transporting substance, the board 15 containing the organic light emitting substance, and the tungsten wire 16 wound with the aluminum wire by the alternating current power supply 18 in order in the chamber 1 so that a predetermined current is passed. Films can be sequentially formed to a thickness.

In the present invention, the IT
Carrier transport layer 10, organic light emitting layer 11, and aluminum electrode 12 formed on glass substrate 13 having O film
A polyparaxylene film is formed as a protective film on the entire exposed portion of the substrate.

First, a predetermined flow rate (for example, 3 sccm) of hydrogen gas is supplied into the discharge tube 2 via a mass flow controller.
When the flow is adjusted to a predetermined pressure (for example, about 4 × 10 ⁻² Pa) and the 13.56 MHz high frequency power supply 5 is operated, plasma is generated in the discharge tube 2 by electrodeless discharge. When an arbitrary negative voltage is applied to the substrate holder 6 using the DC power supply 8 in such a state, hydrogen ions in the plasma are extracted and carrier transport provided on the substrate attached to the substrate holder 6 is performed. The entire exposed surfaces of the layer 10, the organic light emitting layer 11, and the aluminum electrode 12 are irradiated with hydrogen ions.

At the same time as this series of operations, the following structural formula (1)
An AC current is applied to the boat 17 containing the compound represented by
A polyparaxylene film is formed as a protective film on the entire exposed surface of the organic light emitting layer 11 and the aluminum electrode 12.

[0030]

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Here, 0 to -150
While applying a voltage up to V, the polyparaxylene film is formed until the thickness of the polyparaxylene film becomes 0.5 μm. Thereafter, the film is taken out into the atmosphere and used with a surface analyzer (manufactured by RIKEN KEIKI: AC-1). The work function was measured. The result is shown in FIG.

As shown in FIG. 2, when the voltage applied to the substrate holder (synonymous with the kinetic energy of hydrogen ions) increases, the work function of the film exceeds 5.0 eV, and the denseness of the film improves, and -50 V The value reached its maximum.

However, when the film was formed without applying a voltage, the work function of the film was very small, indicating that the film did not sufficiently cover the aluminum electrode.

When the applied voltage exceeds -150 V,
The work function was lowered, which revealed that the bonding state of the film was not sufficient.

The meaning that the voltage applied to the substrate holder and the energy of hydrogen ions are synonymous is as follows.
This is because the kinetic energy of the hydrogen ions accelerated by the applied voltage is substantially equal to the applied voltage. Specifically, the energy of hydrogen ions of 20 eV corresponds to a voltage of 20 V applied to the substrate holder,
eV energy is 100V applied voltage to the substrate holder
Corresponds to.

From the above, the energy of the hydrogen ion is in the range of less than 150 eV, preferably 30 to 100 eV.
It can be seen that if a protective film is formed while irradiating the aluminum electrode with hydrogen ions in the range of (1), a film maintaining a strong bonding state can be obtained.

In the manufacturing method of the present invention, the plasma generation method for extracting positive ions is not limited to the high frequency discharge device shown in FIG. 1, but may be any method such as a plasma generation method using a pressure gradient type plasma gun. Absent.

In the manufacturing method of the present invention, the plasma density to be generated is preferably in the range of 10 ⁸ to 10 ¹³ cm ^-3 , and more preferably in the range of 10 ⁹ to 10 ¹² cm ^-3. Irradiation with a hydrogen ion density that does not give an effect is desirable.

Next, an organic light emitting device which is a specific example of the charge injection type light emitting device of the present invention will be described in more detail.

FIG. 3 is a sectional view showing an example of the organic light emitting device of the present invention. FIG. 3 shows an anode 20 and a light emitting layer 2 on a substrate 19.
1 and a cathode 22 are sequentially provided. The organic light-emitting device used here is useful when it has a single hole transporting ability, electron transporting ability, and luminous performance, or when it is used by mixing compounds having the respective properties.

FIG. 4 is a sectional view showing another example of the organic light emitting device of the present invention. FIG. 4 shows a configuration in which an anode 20, a hole transport layer 23, an electron transport layer 24, and a cathode 22 are sequentially provided on a substrate 19. In this case, the light-emitting substance is a material having either a hole-transporting property or an electron-transporting property or both, and is used in combination with a simple hole-transporting substance or an electron-transporting substance having no light-emitting property. Useful in cases. In this case, the light emitting layer 2
1 comprises a hole transport layer 23 and an electron transport layer 24.

FIG. 5 is a sectional view showing another example of the organic light emitting device of the present invention. FIG. 5 shows a configuration in which an anode 20, a hole transport layer 23 as a carrier transport layer, a light emitting layer 21, an electron transport layer 24 as a carrier transport layer, and a cathode 22 are sequentially provided on a substrate 19.

FIG. 6 is a sectional view showing another example of the organic light emitting device of the present invention. FIG. 6 shows an anode 20, a light emitting layer 21, an electron transport layer 24 as a carrier transport layer and a cathode 2 on a substrate 19.
2 is provided sequentially.

The organic light-emitting devices shown in FIGS. 5 and 6 have separate functions of carrier transport and light emission.
It is used in combination with a compound having hole transporting, electron transporting, and luminescent properties in a timely manner, which greatly increases the degree of freedom in material selection and allows the use of various compounds having different emission wavelengths. Can be diversified. Further, it is also possible to effectively confine holes and electrons (or excitons) in the central light emitting layer to improve the light emission efficiency.

The organic light-emitting device having the structure of the present invention is extremely excellent in hole injection property and electron injection property as compared with the conventional organic light-emitting element, and may be used in any of the embodiments shown in FIGS. Things are possible.

In general, an organic light emitting device is a charge injection type light emitting device, and strongly depends on the amount of carriers (holes or electrons) injected from an electrode. It is desirable that the carrier injection from the electrodes (anode and cathode) is always constant even when used for a long time.

In the organic light-emitting device of the present invention, as a component of the light-emitting layer, a polymer-based hole-transporting compound or a conventionally known hole-transporting luminescent compound (for example,
5), a dopant luminescent material (for example, a compound represented by Chemical formula 6 to 7), an electron-transporting luminescent compound (for example, a compound represented by Chemical formula 8 to 9), or an electron-transport property Two or more materials (for example, compounds shown in Chemical formulas 10 to 12) can be used as needed.

[0048]

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[0049]

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[0050]

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[0051]

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[0052]

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[0053]

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[0054]

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[0055]

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[0056]

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[0057]

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[0058]

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In the organic light-emitting device of the present invention, the light-emitting layer generally forms a thin film by vacuum evaporation or a combination with an appropriate binder.

The binder can be selected from a wide range of binder resins, for example, polyvinyl carbazole resin, polycarbonate resin, polyester resin, polyarylate resin, butyral resin, polystyrene resin, polyvinyl acetal resin, diallyl phthalate resin, acrylic resin , Methacrylic resin, phenolic resin, epoxy resin,
Examples include, but are not limited to, silicone resins, polysulfone resins, urea resins, and the like. These may be used alone or as a copolymer in one kind or as a mixture of two or more kinds.

As the anode material, ITO (indium-tin alloy) which is transparent and has a large work function is used.

On the other hand, silver, lead, tin, magnesium, aluminum, calcium, manganese, indium, chromium, or an alloy thereof having a small work function is used as a cathode material.

The organic light-emitting device of the present invention comprises a conventional incandescent lamp,
Unlike fluorescent lamps or light emitting diodes, large areas,
It is a high-resolution, thin, light-weight, high-speed, fully solid-state device that can be used for EL panels that may meet advanced requirements.

[0064]

The present invention will be specifically described below with reference to examples.

<Examples 1 to 7 and Comparative Examples 1 to 3> A 120 nm-thick IT was formed on a glass substrate by sputtering.
The ITO substrate on which the O film was formed was held in the substrate holder of the apparatus shown in FIG.

Next, the inside of the chamber of the apparatus is about 1.3 × 1
After evacuating to 0 ^-4 Pa, a hole transport layer (50 nm thick) made of a compound represented by the following structural formula (2)
m), and a light emitting layer (film thickness: 50 nm) made of Alq _{3 represented} by the following structural formula (3), and a cathode (film thickness: 120 nm) made of Al were sequentially formed by vacuum evaporation.

[0067]

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Next, hydrogen gas was flowed through the mass flow controller at a flow rate of 3.6 sccm, and the pressure in the discharge tube was adjusted to about 5.3 × 10 ^-2 Pa.

Next, a high frequency power supply of 13.56 MHz was operated to generate hydrogen plasma in the discharge tube, and then a voltage of -10 V (corresponding to an energy of 10 eV) was applied to the substrate holder, and at the same time, the above-mentioned structural formula (1) was applied. ) Was heated and evaporated from the boat 17 to form a protective film (film thickness 0.5 μm), whereby the device of Example 1 was produced.

The devices fabricated in the same manner as in Example 1 except that the voltage applied to the substrate holder was the voltage shown in Table 1 below were used for Comparative Examples 1, 2 to 7, and 2 respectively.
Device. For comparison, a device in which a conventional thermosetting epoxy resin was coated on a device without a protective film was used as a device of Comparative Example 3.

The device manufactured in this manner was placed in air (2
Under conditions of 5 ° C. and 70% RH), an initial luminance of 300 cd /
m ² , and a brightness half-life life test was performed. Table 1 shows the results together with the work function values of the polyparaxylene film.

[0072]

[Table 1]

As is apparent from the results, the work function of the device in which the energy of hydrogen ions was less than 150 eV and the protective film was formed exceeded 5.0 eV. Further, it can be seen that the life characteristics of the device of the present invention in which the protective film having the work function exceeding 5.0 eV is formed are greatly improved.

[0074]

As described above, according to the manufacturing method of the present invention, a polyparaxylene film having extremely low gas and water vapor permeability is formed by using hydrogen ions of a specific energy, thereby obtaining a polyparaxylene film. The work function representing the bonding state of the xylene film increases, and a polyparaxylene film having a work function of 5.0 eV or more can be formed, and the denseness, strength, and adhesiveness of the film can be improved. As a result, the life characteristics of the device are greatly improved.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an example of an apparatus for forming an element by forming a polyparaxylene film according to the present invention as a protective film.

FIG. 2 is a diagram showing a change in work function of a polyparaxylene film with respect to film forming conditions (ion energy or applied voltage) of a protective film according to the present invention.

FIG. 3 is a sectional view showing an example of the organic light emitting device of the present invention.

FIG. 4 is a sectional view showing another example of the organic light emitting device of the present invention.

FIG. 5 is a sectional view showing another example of the organic light emitting device of the present invention.

FIG. 6 is a sectional view showing another example of the organic light emitting device of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Chamber 2 Discharge tube 3 High frequency coil 4 Quartz tube 5 High frequency power supply 6 Substrate holder 7 Ammeter 8 DC power supply 9 Capacitor 10 Carrier transport layer 11 Organic light emitting layer 12 Aluminum electrode 13 Substrate having ITO film 14 Boat (with carrier transport material) Reference Signs List 15 boat (containing organic luminescent material) 16 aluminum wire wound tungsten wire 17 boat (containing protective film material) 18 AC power supply 19 substrate 20 anode 21 luminescent layer 22 cathode 23 hole transport layer 24 electron transport layer

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Koichi Suzuki 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Kazunori Ueno 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon (72) Inventor Hiroshi Tanabe 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Andreessen Sven 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Tatsuto Kawai 3-30-2 Shimomaruko, Ota-ku, Tokyo F-term in Canon Inc. (reference) 3K007 AB11 AB13 AB18 CA01 CB01 DA01 DB03 EA01 EB00 FA01 FA02

Claims (4)

[Claims] 1. A charge injection type light emitting device having an organic light emitting layer and a carrier transporting layer between a pair of electrodes at least one of which is transparent, wherein the organic light emitting layer, the carrier transporting layer, and the surface exposed portions of the electrodes are: A charge injection type light emitting device comprising a protective film made of a polyparaxylene film having a work function of 5.0 eV or more. 2. A method for manufacturing a charge-injection light-emitting element having an organic light-emitting layer and a carrier transport layer between a pair of electrodes, at least one of which is transparent, wherein hydrogen ions having an energy range of less than 150 eV are
Irradiating the organic light-emitting layer, the carrier transport layer, and the exposed surface of the electrode to form a polyparaxylene film covering the exposed surface. 3. The method for manufacturing a charge injection type light emitting device according to claim 2, wherein hydrogen ions in an energy range of 30 to 100 eV are irradiated. 4. The polyparaxylene film has a work function of 5.0 eV or more.
3. The method for producing a charge injection type light emitting device according to item 1.