JP3449020B2 - EL device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting element widely used as various display devices, which has a low driving voltage,
The present invention relates to an electroluminescent device having high brightness and excellent stability.

[0002]

2. Description of the Related Art Electroluminescent devices have been researched by many researchers because they are self-luminous and can display brighter and sharper images than liquid crystal devices.

At present, as an electroluminescent device which has reached a practical level, there is a device using ZnS which is an inorganic material.

However, such an inorganic electroluminescent device requires a driving voltage of 200 V or more for emitting light and has not been widely used.

On the other hand, an organic electroluminescence device, which is an electroluminescence device using an organic material, is far from a practical level in the past, but in 1987, a C.D. W. The laminated structure element developed by Tang et al. Has dramatically improved its characteristics.

[0006] They have a structure in which a vapor-deposited film is stable and stack a phosphor capable of transporting electrons and an organic material capable of transporting holes, and both carriers are injected into the phosphor to emit light. succeeded in.

As a result, the luminous efficiency of the organic electroluminescent device was improved, and light emission of 1000 cd / m ² or more was obtained at a voltage of 10 V or less.

[0008] Since then, many researchers have conducted research to improve the characteristics, and at present, 10,000 cd / m ²
The above emission characteristics are obtained.

The basic light emitting characteristics of such an organic electroluminescent device are already in a practical range, and the biggest problem that hinders its practical use is the lack of stability of the light emitting characteristics during driving.

Specifically, the light emission luminance is lowered, a dark spot, which is a non-light emitting region, is generated, or the element is short-circuited to cause destruction.

[0011]

SUMMARY OF THE INVENTION In view of the above situation, the present invention solves the technical problems of the conventional electroluminescent device, has a low driving voltage, high brightness, and is excellent in light emission stability. the purpose is to provide a novel electroluminescent device capable of realizing a light emitting element, in particular a reduction in luminance during continuous light emission is to provide a much better electroluminescence device.

[0012]

In order to achieve the above object, the present inventors made various electroluminescent devices as prototypes and evaluated the stability of light emission.

As a result, it has been found that the electroluminescence device of the present invention greatly improves the light emission stability.

The steps will be sequentially described below. In the present invention, a mixed layer of the amine compound and the light emitting material described in the following (Chemical formula 5 ), (Chemical formula 6 ), (Chemical formula 7 ) and (Chemical formula 8 ) was provided in contact with the luminous layer.

[0015]

[Chemical 5]

[0016]

[Chemical 6]

[0017]

[Chemical 7]

[0018]

[Chemical 8] However, R ₁ and R ₂ in (Chemical Formula 5 ) are a hydrogen atom, a lower alkyl group, a lower alkoxy group, a phenyl group, a phenyl group having a lower alkyl group or a lower alkoxy group as a substituent, and R ₃ is a hydrogen atom or a methyl group. , A methoxy group, or a chlorine atom, and at least one of R ₁ and R ₂ is a phenyl group having a normal butyl group, an isobutyl group, a secondary butyl group, a tertiary butyl group, a phenyl group, a lower alkyl group or a lower alkoxy group. Represents

R ₄ , R ₅ and R ₆ in (Chemical Formula 6 ) may be the same or different and represent a hydrogen atom, a lower alkyl group, a lower alkoxy group or a substituted or unsubstituted aryl group, and R ₇ Represents a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a chlorine atom, and A ₁ represents a substituent having a structure of any of the following (A) to (M).

[0020]

[Chemical 9] Here, R ₈ in (C) represents a hydrogen atom, a methyl group, a methoxy group, or a chlorine atom.

R ₉ and R ₁₀ in the chemical formula 7 represent a hydrogen atom, a lower alkyl group, a lower alkoxy group or a substituted or unsubstituted phenyl group, and R ₁₁ represents a hydrogen atom, a methyl group, a methoxy group or chlorine. Represents an atom.

In the formula ( 8 ), R ₁₂ and R ₁₃ may be the same or different and each represents a hydrogen atom, a lower alkyl group, a lower alkoxy group or a substituted or unsubstituted aryl group, and R ₁₄ is hydrogen. Represents an atom, a lower alkyl group, a lower alkoxy group, or a chlorine atom, and A ₂ represents a substituent having a structure of any of (A) to (M) below.

[0023]

[Chemical 10] Here, R ₈ in (C) represents a hydrogen atom, a methyl group, a methoxy group, or a chlorine atom.

Examples of the method for forming the mixed layer include a dry film forming method such as a vacuum vapor deposition method and a wet film forming method such as a spin coating method.

Further, in the vacuum vapor deposition method, it is preferable that different materials are simultaneously vapor-deposited from a plurality of vapor deposition sources to form a mixed layer. However, a plurality of materials are mixed and vapor deposition is performed using a single vapor deposition source. It is also possible to create mixed layers. The thickness of the mixed layer is preferably 100 nm or less, more preferably 50 nm or less.

As the light emitting material, various materials such as various metal complex compounds, organic dye compounds such as oxadiazole derivatives, and polymer compounds such as polyparaphenylene vinylene can be used. Basically, the same material is suitable for the light emitting material used for the material and the mixed layer.

Further, by adding a dopant such as quinacridone or coumarin to the light emitting layer, a higher performance electroluminescent device can be manufactured.

Further, as the A amine compound may be mixed with the light emitting material to choose more from one of the above.

Further preferably provided a hole transport layer for improving the injection of holes from the positive electrode.

This hole transport layer may be formed of a single compound or a plurality of compounds, may be a single layer or may be laminated, and it is more preferable to use the amine compound shown in the present invention. .

Further, even better when it improves the injection of electrons from the cathode providing an electron transport layer between the negative electrode and the light emitting layer.

[0032]

The amine compound in the constitution of the present invention is a compound having an excellent hole transporting property with improved heat resistance. In the present invention, a layer in which such a compound and a light emitting material are mixed is brought into contact with the light emitting layer. It has the element configuration provided.

Therefore, the deterioration of the interface of the light emitting layer when light is emitted continuously is greatly suppressed, and the light emission stability is significantly improved.

[0034]

EXAMPLES Hereinafter, the present invention will be described more specifically by way of examples.

The present invention is not limited to these. In the following examples, tris (8-quinolinol) aluminum (Al
Examples of an element having an anode, a hole transport layer, a mixed layer, a light emitting layer, and a cathode are shown by using q), but the technical idea of the present invention is not limited by the specific configuration of these examples. It goes without saying that you do not receive it.

Example 1 Hereinafter, Example 1 of the present invention will be described.

FIG. 1 shows a perspective view of the electroluminescent device of this embodiment. In FIG. 1, 1 is a glass electrode, 2 is a transparent electrode, 3 is a hole transport layer, 4 is a mixed layer, 5 is a light emitting layer, and 6 is an electrode.

In this electroluminescent device, an ITO electrode is formed in advance as a transparent electrode 2 on a glass substrate 1, a hole transport layer 3, a mixed layer 4 of an amine compound and a light emitting material, a light emitting layer 5, and an aluminum / Lithium (Al / Li)
The electrode 6 is vapor-deposited in this order to form a laminated structure, and the manufacturing process thereof will be described in more detail.

First, the glass substrate 1 (IT
(O electrode 2 is already formed), R ₁ = (Formula 5 )
The amine compound (1) having p-t-C ₄ H ₉ , R ₂ = H, and R ₃ = H, and Alq purified as an electron-transporting light-emitting material were set in a vapor deposition apparatus.

Next, after exhausting to 10 ^-6 torr,
The amine compound (1) is vapor-deposited at a rate of 0.1 nm / sec,
The hole transport layer 3 was formed to a thickness of 50 nm.

Next, the amine compound (1) and Alq are vapor-deposited at different rates from each other at a rate of 0.1 nm / sec to form the mixed layer 4 of the amine compound (1) and the luminescent material at 30 nm.
Formed.

Next, the light emitting layer 5 is vapor-deposited with Alq of 0.1 n.
The light emitting layer 5 was laminated at a speed of m / sec to a thickness of 50 nm.

Finally, the vapor deposition of the Al / Li electrode 6 is 1 nm.
Electrode / 6
Were laminated to produce an electroluminescent device.

All of these vapor depositions were continuously performed without breaking the vacuum, and the film thickness was monitored by a crystal oscillator.

Immediately after the device was manufactured, the electrode was taken out in dry nitrogen, and the characteristics were continuously measured.

Here, the emission characteristics of the obtained device is 100.
It was defined as the emission luminance when a current of mA / cm ² was applied.

The emission stability is 500 cd / m ²
The current for obtaining the luminescence was continuously applied, and the change in the luminescence brightness at that time was measured.

In addition, the life of light emission is reduced to 250, which is half the brightness.
It was defined as the time to reach cd / m ² .

As a result, the emission characteristic was 2500 cd / m ^2.
And the emission life was 2100 h.

Then, for comparison, the amine compound (1)
And an Alq mixed layer were not formed, and an electroluminescent device was produced in the same manner as described above, and the characteristics were examined.

As a result, the emission characteristics and the emission lifetime characteristics were 2500 cd / m ² and 620 h, respectively.

Further, instead of the amine compound (1),
An electroluminescent device was produced in the same manner as above except that a typical hole transporting material (abbreviation TPD) shown in the following (Chemical Formula 11 ) was used, and the characteristics were examined.

[0053]

[Chemical 11] As a result, the emission characteristics and emission lifetime characteristics of this comparative example were 2300 cd / m ² and 150 h, respectively.

As described above, in this example, the electroluminescent device provided with the mixed layer of the amine compound (1) and the light emitting material according to the present invention has excellent light emitting characteristics and the light emitting life is remarkably improved. confirmed.

(Second Embodiment) A second embodiment of the present invention will be described below.

In this example, instead of the amine compound (1), the amine compound (2) (R ₁ = p-iso) was used.
-C ₄ H ₉ , R ₂ = H, R ₃ = H), (3) (R ₁ = p-t-C
₄ H ₉ , R ₂ = p-t-C ₄ H ₉ , R ₃ = H), (4) (R ₁ =
_{p-C 6 H 5, R} 2 = p-C 6 H 5, R 3 = H), (5) (R 1
_{= P-CH 3 -C 6 H} 4, R 2 = p-CH 3 -C 6 H 4, R 3 = H)
An electroluminescent device was produced in the same manner as in Example 1 except that was used, and its characteristics were evaluated.

Further, for comparison, an element having no mixed layer of each amine compound and the light emitting material was prepared and its characteristics were evaluated.

The results are shown in (Table 1) below.

[0059]

[Table 1] As described above, in this example, the electroluminescent device using the mixed layer of the amine compounds (2) to (5) and the light emitting material according to the present invention has excellent light emitting characteristics and further has a significantly improved light emitting life. Was confirmed.

(Third Embodiment) A third embodiment of the present invention will be described below.

[0061] In the present embodiment, in place of the amine compound (1), respectively, an amine compound of (Formula 6) (6)
(R ₄ = H, R ₅ = H, R ₆ = H, R ₇ = H, A ₁ =
(A)), (7) (R ₄ = H, R ₅ = H, R ₆ = H, R ₇ =
H, R ₈ = H, A ₁ = (C)), (8) (R ₄ = p-t-C ₄
H ₉ , R ₅ = p-t-C ₄ H ₉ , R ₆ = H, R ₇ = H, R ₈ =
H, A ₁ = (C)), (9) (R ₄ = H, R ₅ = H, R ₆ =
H, R ₇ = H, A ₁ = (F), (10) (R ₄ = H, R ₅
= H, R ₆ = H, R ₇ = H, A ₁ = (H)), an electroluminescent element was produced in the same manner as in Example 1 and its characteristics were evaluated.

Further, for comparison, an element having no mixed layer of each amine compound and the light emitting material was prepared and the characteristics were evaluated.

The results are shown in (Table 2) below.

[0064]

[Table 2] As described above, in this example, the electroluminescent device using the mixed layer of the amine compounds (6) to (10) and the light emitting material according to the present invention has excellent light emitting characteristics and further has a significantly improved light emitting life. Was confirmed.

(Fourth Embodiment) The fourth embodiment of the present invention will be described below.

In this example, instead of the amine compound (1), the amine compound (11) of the above (Chemical Formula 7 ) was used.
(R ₉ = H, R ₁₀ = H, R ₁₁ = H), (12) (R ₉ = p
-CH ₃ , R ₁₀ = p-CH ₃ , R ₁₁ = CH ₃ ) (13) (R _{9
= P-t-C 4 H} 9, R 10 = p-t-C 4 H 9, R 11 = H),
(14) (R ₉ = p-iso-C ₄ H ₉ , R ₁₀ = p-iso-
C ₄ H ₉ , R ₁₁ = H), (15) (R ₉ = p-C ₆ H ₅ , R _{10
= P-C 6 H 5,} R 11 = H) except for using is to produce electroluminescence device in the same manner as in Example 1, and the characteristics were evaluated.

Further, for comparison, an element having no mixed layer of each amine compound and the light emitting material was prepared and its characteristics were evaluated.

The results are shown in (Table 3) below.

[0069]

[Table 3] As described above, in this example, the electroluminescent device using the mixed layer of the amine compounds (11) to (15) and the light emitting material according to the present invention has excellent light emitting characteristics and further has a significantly improved light emitting life. Was confirmed.

(Fifth Embodiment) A fifth embodiment of the present invention will be described below.

In this example, instead of the amine compound (1), the amine compound (16) of the above (Chemical Formula 8 ) was used.
(R ₁₂ = p-CH ₃ , R ₁₃ = p-CH ₃ , R ₁₄ = H, A ₂ =
(A)), (17) (R ₁₂ = H, R ₁₃ = H, R ₁₄ = H,
R ₈ = H, A ₂ = (C)), (18) (R ₁₂ = p-t-C ₄
H ₉ , R ₁₃ = p-t-C ₄ H ₉ , R ₁₄ = H, R ₈ = H, A ₂ =
(C)), (19) (R ₁₂ = H, R ₁₃ = H, R ₁₄ = H,
A ₂ = (F)), (20) (R ₁₂ = H, R ₁₃ = H, R ₁₄
= H, A ₂ = (H)) was used to manufacture an electroluminescence device in the same manner as in Example 1, and the characteristics thereof were evaluated.

Further, for comparison, an element having no mixed layer of each amine compound and the light emitting material was prepared and the characteristics were evaluated.

The results are shown in Table 4 below.

[0074]

[Table 4] As described above, in this example, the electroluminescent device using the mixed layer of the amine compounds (16) to (20) and the light emitting material according to the present invention is excellent in light emitting characteristics and further has a significantly improved light emitting life. Was confirmed.

(Sixth Embodiment) The sixth embodiment of the present invention will be described below.

Electroluminescence was performed in the same manner as in Example 1 except that the amine compound (1) and the amine compound (7) were used in place of the amine compound (1) to form a mixed layer with Alq as a light emitting material. A device was prepared and its characteristics were evaluated.

As a result, the emission characteristics were 2400 cd / m ^2.
And the life of light emission was 2500 h.

For comparison, amine compounds (1) and (7)
And an Alq mixed layer were not formed, and an electroluminescent device was produced in the same manner as above, and the characteristics were examined.

As a result, the emission characteristics and the emission lifetime characteristics were 2500 cd / m ² and 620 h, respectively.

As described above, in this example, the electroluminescent device provided with the mixed layer of the amine compounds (1) and (7) and the light emitting material according to the present invention has excellent light emitting characteristics and has a significantly long light emitting life. It was confirmed to improve.

[0081]

INDUSTRIAL APPLICABILITY As described above, the present invention is an electroluminescent device provided with an optimized mixed layer of an amine compound and a light emitting material, and by using the material and constitution of the present invention, conventional electroluminescence is achieved. It is possible to realize an electroluminescent device in which the light emission stability, which has been the greatest technical issue of the device, is significantly improved.

[Brief description of drawings]

FIG. 1 is a partially enlarged cross-sectional perspective view showing a configuration of an electroluminescent device according to an embodiment of the present invention.

[Explanation of symbols]

1 glass substrate 2 transparent electrode 3 Hole transport layer 4 Mixed layer of amine compound and luminescent material 5 Electron transport layer and light emitting layer 6 Al / Li electrode

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-8-96964 (JP, A) JP-A-8-48656 (JP, A) JP-A-5-182762 (JP, A) JP-A-3- 114197 (JP, A) JP 4-334894 (JP, A) JP 3-190088 (JP, A) JP 7-53955 (JP, A) JP 6-1972 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H05B 33/14 H05B 33/22 C09K 11/06 CA (STN) REGISTRY (STN)

Claims (7)

(57) [Claims] 1. An electroluminescent device comprising a mixed layer of an amine compound represented by the following general formula and a light emitting material provided in contact with the light emitting layer. [Chemical 1] However, R ₄ , R ₅ , and R _{6, which} may be the same or different, each represents a hydrogen atom, a lower alkyl group, a lower alkoxy group, a substituted or unsubstituted aryl group, and R ₇ is a hydrogen atom,
Lower alkyl group, a lower alkoxy group or a chlorine atom,, A ₁ is to <br/> table a substituent having one of the following structures. [Chemical 2] 2. An electroluminescent device comprising a mixed layer of an amine compound represented by the following general formula and a light emitting material provided in contact with the light emitting layer. [Chemical 3] However, R ₁₂ and R ₁₃ may be the same or different and each represents a hydrogen atom, a lower alkyl group, a lower alkoxy group or a substituted or unsubstituted aryl group, and R ₁₄ is a hydrogen atom, a lower alkyl group or a lower alkoxy group. , Or a chlorine atom, and A ₂ represents a substituent having one of the following structures.
You [Chemical 4] 3. An electroluminescent device, characterized in that a mixed layer of a material containing at least two kinds selected from the amine compounds according to claim 1 or 2 and a light emitting material is provided in contact with the light emitting layer. 4. An anode, a mixed layer of an amine compound and a light emitting material,
Electroluminescent device according to any one of claims 1 consisting of the light emitting layer and the cathode 3. 5. anode, a hole transport layer, a mixed layer of an amine compound as a light emitting material, claim 1 consisting of light-emitting layer and a cathode 3
The electroluminescent element according to any one of 1. 6. The light-emitting layer and the electroluminescent device according to claim 4 or 5, wherein an electron transporting layer disposed between the cathode. 7. The electroluminescent device according to any one of the light emitting material of the mixed layer from claim 1 and a light-emitting material is the same light-emitting layer 6.