JP3011277B2 - Manufacturing method of organic electroluminescence device - Google Patents

Description

The present invention relates to a method for manufacturing an organic electroluminescence device used for a flat light source, a display, and the like.

[Conventional technology]

Electroluminescent elements (hereinafter referred to as EL elements) have the characteristics that they are self-luminous, have high visibility, are completely solid, have excellent impact resistance, and can be used to manufacture large-area surface-emitting devices. Is currently an inorganic phosphor
EL devices using ZnS: Mn have been put to practical use. However, an inorganic EL element requires a high applied voltage of about 200 V to emit light, and the driving method is complicated.

Organic EL devices, on the other hand, can greatly reduce the applied voltage. Recently, a new type of organic thin film with a two-layer structure has been developed, which has higher luminance (1000 cd / m ² or more) with lower voltage application (10 V or less). The obtained organic EL device has been reported (Applied Physics Letters, vol. 51, p. 913, 1987).
Also, JP-A-2-8287, JP-A-2-8288, JP-A-2-82
89, etc., by developing new organic phosphors and changing the layer structure (Chemical and Industrial, Vol. 42, p. 2023, 1989) It has been reported. As described above, since the organic EL element can emit light of each color, has a simple configuration, and can be easily manufactured, it has attracted attention as an inexpensive large-area full-color display element, for example.

However, since the organic EL thin film has a thickness of 0.1 to 0.3 μm, pinholes are easily generated, and it is difficult to increase the area.
According to the vapor deposition method, the uniformity of the formed film is improved and pinholes are less likely to occur. However, the crystallization of the deposited film proceeds, and it is often obtained as a microcrystalline aggregate thin film.

[Problems to be solved by the invention]

When forming a thin film for organic EL by vapor deposition method,
Crystallization progresses and is often obtained as a microcrystalline aggregate thin film. In such a case, uniformity in the film direction due to crystallization is lost, emission intensity becomes uneven, and uniform light emission occurs in a large area. The organic EL device shown cannot be obtained.

An object of the present invention is to provide a manufacturing method for manufacturing an organic EL device in which the above-mentioned disadvantages are improved.

[Means for solving the problem]

The present inventors have found that the cause of the emission intensity unevenness observed in the organic EL element is due to crystallization of the deposited film, and when the organic EL element is manufactured by forming a thin film on a substrate by an evaporation method, the deposition step is performed. At this time, the present inventors have found that an organic EL element having no uneven emission intensity can be manufactured by sufficiently cooling the substrate to prevent crystallization of the vapor-deposited thin film and to form the thin film in an amorphous state.

That is, the present invention is a method for manufacturing an organic EL device, which comprises cooling a substrate during an evaporation step in an organic EL device formed by forming a thin film on a substrate by an evaporation method.

Organic EL devices are available in two-layer and three-layer structures.
An organic EL device is manufactured by providing these layer configurations on a transparent electrode serving as a substrate and providing a counter electrode thereon. In the case of a two-layer structure, it consists of a combination of a hole transporting layer and an electron transporting light emitting layer or a combination of an electron transporting layer and a hole transporting light emitting layer,
In the case of a three-layer structure, the light emitting layer is sandwiched between the hole transport layer and the electron transport layer.

As the charge transporting agent, a compound used in an organic photoreceptor for electrophotography or a compound having charge transporting ability can be used. Examples of the hole transport agent include porphyrin compounds such as porphine, tetraphenylporphine copper, phthalocyanine, copper phthalocyanine, and titanium phthalocyanine oxide; 1,1-bis {4- (di-p-tolylamino) phenyl} cyclohexane; 4 ', 4 "-trimethyltriphenylamine, N, N, N', N'-tetrakis (p
-Tolyl) -p-phenylenediamine, 1- (N, N, -di-p-tolylamino) naphthalene, 4,4'-bis (dimethylamino) -2,2'-dimethyltriphenylmethane,
N, N, N ', N'-tetraphenyl-4,4'-diaminobiphenyl, N, N'-diphenyl-N, N'-di-m-tolyl-4,
Aromatic tertiary amines such as 4'-diaminobiphenyl and N-phenylcarbazole, 4-di-p-tolylaminostilbene, 4- (di-p-tolylamino) -4 '-[4-
(Di-p-tolylamino) styryl] stilbene and the like. Examples of the electron transport agent include 2- (p-tert-butylphenyl) -5- (p-biphenylyl) -1,3,5-oxadiazole, tetracyanoquinodimethane, and 3,5-dimethyl-3. ', 5'-di-tert
-Butyl-4,4'-diphenoquinone and the like.

As the organic fluorescent substance for the light emitting layer, for example, Tris (8
Chelating oxinoid compounds such as -quinolinol) aluminum, bis (8-quinolinol) magnesium, and tris (5-chloro-8-quinolinol) gallium;
Aromatic compounds such as 4-bis (4-ethylstyryl) benzene, 1,2,3,4-tetraphenylcyclopentadiene, 1,2,3,4,5-pentaphenylcyclopentadiene, perylene pigments, chelates Chelate compounds of 2,2'-bipyridine compounds and salicylidene-0-aminophenol derivatives, and 4- (di-p-tolylamino) -4'-chlorostilbene and 4- (di-p-tolylamino) -β-
Phenylstilbene, 4,4'-dimethoxy-4 "-(1
-Naphthylvinyl) triphenylamine and the like.

Glass, plastic, quartz, etc. are used for the support of the organic EL element. Metals such as gold, aluminum, indium, silver, magnesium, indium-tin-oxide (ITO), tin oxide, and zinc oxide are formed on this substrate. An ultra-thin electrode made of a thin film or the like is formed by a vapor deposition method or the like to obtain a translucent or transparent electrode. A charge transport layer and a light emitting layer are laminated thereon, and furthermore, an electrode similar to that described above is formed thereon to manufacture an organic EL device. A DC voltage is applied to this to emit light.

〔Example〕

 Hereinafter, the present invention will be described specifically with reference to examples.

Example 1 A commercially available ITO glass electrode (transparent conductive film (standard type) manufactured by Matsuzaki Vacuum Co., Ltd.) was deposited on a vapor deposition device (manufactured by Vacuum Instrument Industry Co., Ltd.).
(LC-6F type) substrate holder, copper phthalocyanine (Cu · Pc) was placed in a heating boat, and the pressure was reduced to 1 × 10 ⁻⁵ Torr. The heating boat was heated to 300 ° C., and deposition was performed at a deposition rate of 500 ° C./min to form a hole injecting layer of copper phthalocyanine having a thickness of 1000 μm on the ITO glass electrode. At this time, ITO
The glass electrode was cooled to −100 ° C. to obtain an amorphous vapor-deposited film of copper phthalocyanine as shown in FIG. Next, tris (8-quinolinol) aluminum (Alq3)
Heat the other heating boat containing the
A light emitting layer having a thickness of 1000 mm was formed on the hole injection layer at a deposition rate of Å / min. Further, a 5000 mm-thick magnesium vapor-deposited film is formed thereon in a size of 3 mm x 8 mm to serve as a counter electrode, and an organic
An EL device was manufactured. Also, under the same conditions as those described above,
Only the cooling temperature of the ITO glass electrode was changed, and the one cooled to −40 ° C. and the one cooled to −160 ° C. were produced.

DC 2 with ITO electrode as positive electrode and magnesium electrode as negative electrode
When a voltage of 2 V was applied, bright green light was emitted. 8 light emitting surfaces
Divided into small areas, 1mmφ for each small area
Is a luminance measuring point (Minolta Camera Co., Ltd.)
When the luminance was measured using LS-110, the results shown in Table 1 were obtained.

Average luminance is 437cd / m ²
An element was obtained.

The diffraction intensities of the three types of organic EL devices were measured by Rigaku Denki Co., Ltd.
As a result of the measurement using the RAD-C system manufactured by Asahi Kasei, the diffraction intensity is small as shown in FIG. 2, and it can be seen that crystallization of the deposited film is prevented.

Comparative Example 1 In Example 1, the same procedure as in Example 1 was carried out except that the ITO glass electrode was carried out at room temperature without cooling the electrode during the vapor deposition, and the results shown in Table 2 were obtained.

The average luminance was 154 cd / m ² , and the luminous efficiency was low and the luminous unevenness was large as compared with Example 1. In addition, the result of measuring the diffraction intensity with a RAD-C system manufactured by Rigaku Denki Co., Ltd. shows that the diffraction intensity is large as shown in FIG. 2 and the crystallization of the deposited film is progressing. This comparative example shows that the effect of the present invention is remarkable.

Example 2 A commercially available ITO glass electrode (transparent conductive film (standard type) manufactured by Matsuzaki Vacuum Co., Ltd.) was deposited on a vapor deposition apparatus (manufactured by Vacuum Instrument Industry Co., Ltd.).
(LC-6F type) substrate holder, copper phthalocyanine (Cu · Pc) was placed in a heating boat, and the pressure was reduced to 1 × 10 ⁻⁵ Torr. The heating boat was heated to 300 ° C., and deposition was performed at a deposition rate of 500 ° C./min to form a hole injecting layer of copper phthalocyanine having a thickness of 1000 μm on the ITO glass electrode. At this time, I
The TO glass electrode was cooled to -100 ° C to obtain an amorphous deposited film of copper phthalocyanine. Next, reduce the degree of vacuum to 1 × 10
^The other heating boat containing the salicylidene-0-aminophenol A1 complex was heated to ^-6 Torr and the other heating boat was heated to 320 ° C, and the light emitting layer having a thickness of 2000 mm was deposited on the hole injection layer at a deposition rate of 500 mm / min. Formed. Further, a 5000 mm-thick magnesium vapor-deposited film having a size of 3 mm × 8 mm was formed thereon to serve as a counter electrode, thereby producing an organic EL device.

DC 2 with ITO electrode as positive electrode and magnesium electrode as negative electrode
When 5 V was applied, blue-green light was emitted. The light emitting surface is divided into eight small areas, and each small area is measured at a measuring point of 1 mmφ with a luminance meter (LS manufactured by Minolta Camera Co., Ltd.).
When the luminance was measured using (−110 type), the results shown in Table 3 were obtained.

The average luminance is 201 cd / m ² , and organic EL with little emission unevenness
An element was obtained.

Comparative Example 2 In the same manner as in Example 2, except that the ITO glass electrode was cooled at room temperature without cooling during the vapor deposition in Example 2, the results shown in Table 4 were obtained.

The average luminance was 91 cd / m ² , and the luminous efficiency was low and the luminous unevenness was large as compared with Example 2. This comparative example shows that the effect of the present invention is remarkable.

Example 3 A commercially available ITO glass electrode (transparent conductive film (standard type) manufactured by Matsuzaki Vacuum Co., Ltd.) was deposited on a vapor deposition device (manufactured by Vacuum Instrument Industry Co., Ltd.).
(LC-6F type) is fixed to the substrate holder, and N,
N′-diphenyl-N, N′-di-m-tolyl-4,4′-diaminobiphenyl was added and the pressure was reduced to 1 × 10 ⁻⁵ Torr. The heating boat was heated to 200 ° C., and the deposition was performed at a deposition rate of 500 ° / min.
A hole injection layer of N, N'-di-m-tolyl-4,4'-diaminobiphenyl was formed on the ITO glass electrode. At this time, ITO
The glass electrode was cooled to -100 ° C and N, N'-diphenyl-N,
An amorphous deposited film of N'-di-m-tolyl-4,4'-diaminobiphenyl was obtained. Next, the other heating boat containing tris (8-quinolinol) aluminum was heated to 180 ° C., and the film thickness was set to 1000 ° at a deposition rate of 500 ° / min.
Was formed on the hole injection layer. Further, a 5000 mm-thick magnesium vapor-deposited film having a size of 3 mm × 8 mm was formed thereon to serve as a counter electrode, thereby producing an organic EL device.

DC 4 with ITO electrode as positive electrode and magnesium electrode as negative electrode
When 0 V was applied, green light was emitted. The light-emitting surface was divided into eight small areas, and each small area was measured at a measurement point of 1 mmφ with a luminance meter (LS-Linus manufactured by Minolta Camera Co., Ltd.).
When the luminance was measured using a (110 type), the results in Table 5 were obtained.

The average luminance is 296 cd / m ² , and organic EL with little emission unevenness
An element was obtained.

〔The invention's effect〕

The organic EL device manufactured by the manufacturing method of the present invention,
Since the substrate is cooled during the vapor deposition step, crystallization of the vapor-deposited thin film is prevented, and the vapor-deposited thin film is formed in an amorphous state.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows constituent layers of an organic electroluminescence device obtained by the present invention. FIG. 2 shows an X-ray diffraction pattern of the Cu.Pc thin film, in which the cooling temperature of the ITO glass electrode (substrate) was -160.degree.
(-100 ° C, -40 ° C, room temperature) and the diffraction intensity. The horizontal axis represents the diffraction angle (2θ), and the vertical axis represents the diffraction intensity.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-139893 (JP, A) JP-A-1-1122693 (JP, A) JP-A-61-156786 (JP, A) JP-A-59-156 141218 (JP, A) JP-A-1-292794 (JP, A)

Claims (1)

(57) [Claims] 1. A method for manufacturing an organic electroluminescent device, comprising cooling a substrate during a deposition step in an organic electroluminescent device formed by forming a thin film on a substrate by a vapor deposition method.