JPH06200242A - Organic thin-film luminescent element - Google Patents

Abstract

(57) [Summary] (Modified) [Purpose] To obtain an organic thin film light emitting device having high emission brightness and excellent lifetime stability. [Structure] The distyrylbenzene compound represented by the general formula (I) is used for the hole injection layer. [In the formula (I), R ₁ and R ₂ represent an alkyl group, an alkoxy group and an aryl group, respectively, and R ₃ represents a hydrogen atom, a halogen atom, an alkyl group and an alkoxy group. ]

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic thin film light emitting device used as a light emitting source of various display devices, and more particularly to a substance used for a hole injection layer.

[0002]

2. Description of the Related Art With the increasing demand for flat displays replacing conventional cathode ray tubes, various display devices have been vigorously developed and put into practical use. An electroluminescence element (hereinafter referred to as a light emitting element) also meets such needs, and in particular, as an all-solid-state spontaneous light emitting element, it has attracted attention because of its high resolution and high visibility not found in other displays.

What has been put into practical use at present is that the light emitting layer has a Z layer.
There is a light emitting element using an nS / Mn-based inorganic material. In a light emitting device using an organic material, a stack type light emitting device using a quinolinol compound as a light emitting material and a diamine compound as a charge injection material has already been used by Tan et al.
It was reported that a high brightness of 1000 cd / m ² or more was obtained at low applied voltage (Appl. Phys. Lett. Vol. 51, No. 12,
913, (1987)), and since then, research has been active toward practical application. It is required that the organic light emitting material has excellent film formability and high luminous efficiency and is stable, and that the charge injection material has excellent film formability and has high charge transporting ability and high efficiency of injecting charges into the light emitting layer. JP-A-2-3115
Various materials are known from JP-A-91, JP-A-59-194393, and the like.

In order to apply this light emitting device as a display, it is required to have characteristics such as low voltage driving, high brightness, long life, and full color.

[0005]

In the light emitting device using the above-mentioned ZnS / Mn type inorganic material, the driving voltage required for light emission is as high as about 200 V, the driving method is complicated, the manufacturing cost is high, and the blue light emission efficiency is high. However, there is a problem that it is difficult to realize full color because of low. In a light emitting device using an organic material, full color and low voltage driving can be expected due to the variety of organic materials. However, although the organic material has many features that the inorganic material does not have, an organic light-emitting element that meets all the requirements has not yet been obtained. Therefore, an organic light emitting material and a charge injection material are being energetically searched for along with a device structure and a manufacturing method.

The present invention has been made in view of the above points, and an object thereof is to provide an organic thin film light emitting device having high brightness and excellent life stability by developing a novel hole injection material.

[0007]

The above-mentioned object has an insulating transparent substrate, on which a pair of positive and negative electrodes, a light emitting layer and a charge injection layer sandwiched therebetween are stacked. In the body, the charge injection layer includes at least a hole injection layer of an electron injection layer and a hole injection layer, the hole injection layer includes a distyrylbenzene compound represented by the following general formula (I), and the light emitting layer includes an injection layer. This is achieved by combining the generated electrons and holes to emit light.

[0008]

[Chemical 2]

[In the formula (I), R ₁ and R ₂ represent an alkyl group, an alkoxy group and an aryl group, respectively, and R ₃ represents a hydrogen atom, a halogen atom, an alkyl group and an alkoxy group. ]

[0010]

There is no known example of using the distyrylbenzene compound represented by the general formula (I) as a charge injection material. These inventors have conducted a number of experiments on these compounds in the course of extensive studies on various organic materials in order to achieve the above-mentioned object, and as a result, their technical elucidation has not yet been sufficiently conducted. By using the specific compound represented by the formula (1) as the charge injection material, a good film can be formed, the number of electrical defects such as pinholes generated in the film is small, and the brightness is high and the life stability is excellent. In addition, an organic light emitting device was obtained.

[0011]

EXAMPLES The compounds represented by the general formula (I) used in the present invention can be synthesized by a known method. For example, the compound represented by the general formula (II) and the general formula (II
It can be easily obtained by a condensation reaction (Wittig reaction) with the compound represented by I).

[0012]

[Chemical 3]

[In the formula (II), R ₁ and R ₂ represent an alkyl group, an alkoxy group and an aryl group, respectively, and R ₃ represents a hydrogen atom, a halogen atom, an alkyl group and an alkoxy group. ]

[0014]

[Chemical 4]

The above-mentioned general formula (I) thus obtained
Specific examples of the distyrylbenzene-based compound represented by are as follows.

[0016]

[Chemical 5]

[0017]

[Chemical 6]

Examples of organic light-emitting devices using the distyrylbenzene compound according to the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing an organic light emitting device according to an embodiment of the present invention. (Light emission proceeds in the direction indicated by the arrow in the figure). Transparent insulating substrate 1 such as glass
A semi-permeable film such as gold or nickel or indium tin oxide (I
The positive electrode 2 made of a transparent conductive film such as TO) or tin oxide (SnO ₂ ) is formed by resistance heating vapor deposition, electron beam vapor deposition, or sputtering. This positive electrode 2 has 1 in order to have transparency.
It is desirable to set the thickness to 0 to 300 nm. Next, an organic thin film is sequentially formed on the hole injection layer 3 and the light emitting layer 4. Both layers can be formed by spin coating, casting, the LB method, resistance heating evaporation, electron beam evaporation, or the like, but resistance heating evaporation is preferable from the viewpoint of film uniformity. The thickness of both layers is 10 to 300 nm, preferably 20 to 100 nm.
Finally, the negative electrode 5 is formed by vapor deposition. This negative electrode 5
Materials for use include Mg, Mg / Ag, which have a small work function,
In, Ca, Al or the like is used.

FIG. 2 is a sectional view showing an organic light emitting device according to another embodiment of the present invention. (Light emission proceeds in the direction indicated by the arrow in the figure). On a transparent insulating substrate 1 made of glass or the like, a semi-permeable film made of gold or nickel or indium tin oxide (IT
O), tin oxide (SnO ₂ ) and the like, a positive electrode 2 made of a transparent conductive film is formed in the same manner as in FIG. 1, and three layers of a hole injection layer 3, a light emitting layer 4 and an electron injection layer 7 are formed. This hole injection layer 3,
The thicknesses of the light emitting layer 4 and the electron injection layer 7 are all 10 to 300 nm, preferably 20 to 1 as in the case of FIG.
00 nm. Finally, set the negative electrode 5 to Mg, Mg / Ag,
Deposition is performed using In, Ca, Al, or the like. Example 1 A glass of 50 mm square provided with ITO having a film thickness of about 100 nm was used as a substrate, and the substrate was set in a resistance heating vapor deposition apparatus.
As shown in FIG. 1, the hole injection layer 3 and the light emitting layer 4 were sequentially formed. During film formation, the pressure inside the vacuum chamber was reduced to 1 × 10 ⁻⁴ Pa. The compound (I-6) was used for the hole injection layer 3 and heated at an evaporation source temperature of 100 to 180 ° C. to form a film thickness of 60 nm at a film formation rate of about 0.2 nm / s. Next, without breaking the vacuum of the vacuum chamber, (8-hydroxyquinoline) aluminum represented by the formula (IV) is continuously heated as the light emitting layer 4 in the range of the evaporation source temperature of 100 to 300 ° C., and the film forming rate is about 0. A film thickness of 60 nm was formed at 0.2 nm / s. This sample was taken out of the vacuum chamber, a stainless mask consisting of a dot pattern with a diameter of 5 mm was attached, and it was newly set in the resistance heating vapor deposition device to form a negative electrode 5 by vapor deposition of Mg / Ag alloy (ratio of 10: 1). did. In Example 1, the hole injection layer 3 made of the compound (I-6) was a uniform vapor deposition film, and when a DC voltage of 10 V was applied to the organic light emitting device having a diameter of 5 mm, green light emission was obtained. At this time, the emission center wavelength is 530 nm and the emission luminance is 1000 cd.
/ M ² or more. Further, even in continuous light emission over 1000 hours, good stability was exhibited.

[0020]

[Chemical 7]

Example 2 A glass of 50 mm square provided with ITO having a film thickness of about 100 nm was used as a substrate, and the substrate was set in a resistance heating vapor deposition apparatus.
As shown in FIG. 2, the hole injection layer 3, the light emitting layer 4, and the electron injection layer 7 were sequentially formed. 1 × 10 in vacuum chamber for film formation
^The pressure was reduced to ^-4 Pa. The compound (I-
6) was used, and the evaporation source temperature was heated in the range of 150 to 250 ° C. to form a film thickness of 60 nm at a film forming rate of about 0.2 nm / s. Next, without breaking the vacuum of the vacuum chamber, (8-hydroxyquinoline) aluminum represented by the formula (IV) is continuously heated as the light emitting layer 4 in the range of the evaporation source temperature of 100 to 300 ° C., and the film forming rate is about 0. A film thickness of 60 nm was formed at 0.2 nm / s. Further, similarly, without breaking the vacuum, a perylene tetracarboxylic acid derivative represented by the formula (V) was formed to a film thickness of 70 nm as the electron injection layer 7. This sample was taken out of the vacuum chamber, a stainless mask consisting of a dot pattern with a diameter of 5 mm was attached, and it was newly set in the resistance heating vapor deposition device to form a negative electrode 5 by vapor deposition of Mg / Ag alloy (ratio of 10: 1). did. In Example 2, the hole injection layer 3 made of the compound (I-6) was a uniform vapor deposition film, and when a DC voltage of 10 V was applied to the organic light emitting device having a diameter of 5 mm, green light emission was obtained. At this time, the emission center wavelength was 530 nm and the emission luminance was 1000 cd / m ² or more. Further, even in continuous light emission over 1000 hours, good stability was exhibited.

[0022]

[Chemical 8]

Example 3 An organic light emitting device was formed under the same conditions as in Example 1 except that the compound (I-5) was used for the hole injection layer 3. Also in this Example 3, when a DC voltage of 10 V was applied, green light emission was obtained. The emission center wavelength at this time is 530
nm, the emission luminance was 1000 cd / m ² or more. Further, even in continuous light emission over 1000 hours, good stability was exhibited. Example 4 An organic light emitting device was formed under the same conditions as in Example 2, except that the compound (I-5) was used for the hole injection layer 3.

Also in this fourth embodiment, the DC voltage is 10V.
Was applied, a green light emission was obtained. At this time, the emission center wavelength was 530 nm and the emission luminance was 1000 cd / m ² or more. Further, even in continuous light emission over 1000 hours, good stability was exhibited.

[0025]

According to the present invention, a laminate having an insulating transparent substrate, on which a pair of positive and negative electrodes and a light emitting layer and a charge injection layer sandwiched therebetween are provided, The charge injection layer includes at least a hole injection layer of an electron injection layer and a hole injection layer, the hole injection layer includes a distyrylbenzene compound represented by the general formula (I), and the light emitting layer includes injected electrons. Since it emits light by combining with holes, high-luminance and stable green light emission is realized. Specifically, the emission center wavelength is 530 nm and the emission brightness is 1000 cd.
It is possible to obtain an organic light emitting device exhibiting good stability even in continuous light emission of not less than / m ^{2 for} more than 1000 hours.

[Brief description of drawings]

FIG. 1 is a sectional view showing an organic light emitting device according to an embodiment of the present invention.

FIG. 2 is a sectional view showing an organic light emitting device according to another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Insulating transparent substrate 2 Positive electrode 3 Hole injection layer 4 Light emitting layer 5 Negative electrode 6 DC power supply 7 Electron injection layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Noboru Furusho 1-1, Tanabe Nitta, Kawasaki-ku, Kawasaki-shi, Kanagawa Fuji Electric Co., Ltd.

Claims (3)

[Claims] 1. A laminate having an insulating transparent substrate, wherein a pair of positive and negative electrodes and a light emitting layer and a charge injection layer sandwiched between the electrodes are provided on the insulating transparent substrate. At least a hole injection layer of the injection layer and the hole injection layer,
The hole injecting layer is made of a distyrylbenzene-based compound represented by the following general formula (I), and the light emitting layer combines the injected electrons and holes to emit light, and thus an organic thin film light emitting device. . [Chemical 1] [In the formula (I), R ₁ and R ₂ represent an alkyl group, an alkoxy group and an aryl group, respectively, and R ₃ represents a hydrogen atom, a halogen atom, an alkyl group and an alkoxy group. ] 2. The device according to claim ₁ , wherein R ₁ of the distyrylbenzene compound represented by the general formula (I),
An organic thin film light emitting device characterized in that R ₂ is a phenyl group and R ₃ is a hydrogen atom. 3. The device according to claim ₁ , wherein R ₁ of the distyrylbenzene compound represented by the general formula (I),
An organic thin film light emitting device, wherein R ₂ is a tolyl group and R ₃ is a hydrogen atom.