KR100282023B1 - Low voltage driving organic light emitting device manufacturing method and apparatus used therein - Google Patents

Abstract

The present invention provides a method for manufacturing a low-voltage driving organic light emitting diode having a uniform surface state and thickness, and can be obtained in a high density organic thin film without being influenced by residual solvent, and is manufactured in a state completely blocked from the source of contamination, thereby ensuring reliability and reproducibility. The present invention relates to a device used for fabricating a hole transport layer into a homogeneous mixed thin film of a polyimide formed by vacuum deposition polymerization of a hole transport material, dianhydride and diamine and heat treatment.

Description

Low voltage driving organic light emitting device manufacturing method and apparatus used therein

The present invention provides a method for manufacturing an organic light emitting device capable of low voltage driving, stable and long life by manufacturing a hole transporting layer of an organic light emitting device using a vacuum transport polymerization method as a mixed layer consisting of a hole transporting material and a polymer material, and a device used therein. It is about.

When using organic monomolecules as a material for manufacturing an organic light emitting device, despite the many advantages of the organic monomolecules, they have disadvantages such as instability and bonding to the substrate. Therefore, in order to maintain stability of the organic light emitting device, a host-guest structure using a polymer as a host is used. In the conventional host-guest structure, a thermally and structurally stable polymer (eg, polyimide) is used as a host material as a host material. In this case, the polymer material is difficult to form into a thin film through a direct vacuum deposition process. Due to this, there is thermal stability and the hole transport material is mixed with polyimide dissolved in a solvent to produce a hole transport layer through a wet process (e.g., spin coating), and then a light emitting material (e.g., Alq ₃ ) using a vacuum system. Is deposited and a metal electrode is coated thereon.

At this time, the polyimide is dissolved in a solvent in a polyamic acid state as a precursor, and then applied to a substrate and heat treated to obtain a polyimide thin film. In this case, it is difficult to obtain a very thin and uniform thin film, and the solvent may not be completely removed, causing short-circuit when the light emitting device is driven, causing problems such as instability and driving at high voltage.

Accordingly, an object of the present invention is to provide a method for manufacturing an organic light emitting device capable of low voltage driving and a long lifetime by manufacturing a very thin and uniform organic polymer thin film in the hole transport layer and a device used therein.

1 is a schematic diagram of a vacuum system used in the method of manufacturing an organic light emitting device of the present invention,

2 shows an electron band structure of the organic light emitting device of the present invention,

3 shows a structure of an organic light emitting device manufactured by the method of the present invention,

4 is an electroluminescence intensity curve and a current density curve according to the applied voltage of the organic light emitting diodes manufactured in Examples and Comparative Examples,

5 is an external quantum efficiency curve and luminous efficiency curve according to current density or applied voltage of organic light emitting diodes manufactured in Examples and Comparative Examples,

6 shows electroluminescent spectra according to voltage changes of organic light emitting diodes manufactured in Examples and Comparative Examples,

7 is a light emitting photograph of an organic light emitting device comparing the optimum conditions and conditions other than the optimum.

<Explanation of symbols for main parts of drawing>

I: Loadlock Chamber II: ITO-Glass Substrate Cleaning Chamber

III: Deposition Polymerization (VDP) Chamber IV: Organic Light Emitting Material Coating Chamber

V: Cathode Coating Chamber

1: Magnetic Bar 2: Board Mount

3, 7, 11, 21, 25: substrate holder 8: ion source

4, 9, 12, 19, 23, 27: pumping port 5: quick access door

6, 10, 20, 24: gate valves 12, 13, 14: thermal bath

15, 16, 17: mass flow valve 18: organic vapor nozzle

22 diffusion cell 26 electron beam evaporator

a: glass b: ITO layer (anode)

c: polyimide + hole transport material (hole transport layer)

d: light emitting layer having electron transport characteristics e: cathode

In order to achieve the above object, in the present invention, the hole transport layer and the dianhydride in the method for manufacturing an organic light emitting device by vacuum-depositing a light transport layer and a light emitting layer having electron transport characteristics in a glass-ITO electrode in order The present invention provides a method of manufacturing a low-voltage driving organic light emitting diode, characterized in that the diamine is vacuum-deposited polymerized and heat-treated to produce a homogeneous mixed thin film of polyimide.

In addition, the present invention is a glass-ITO substrate is supplied to the load lock chamber discharged the finished device; An anode substrate cleaning chamber for cleaning the glass-ITO substrate supplied from the load lock chamber through an ion source; A deposition polymerization chamber for generating a mixed thin film of a polyimide formed by depositing and polymerizing a hole transport material, dianhydride and diamine on a pre-clean glass-ITO substrate supplied from the anode substrate cleaning chamber, and the deposition polymerization chamber An organic light emitting material coating chamber for depositing an organic light emitting material on a substrate supplied from the substrate; And a cathode coating chamber for coating the substrate supplied from the organic light emitting material coating chamber with an electron beam evaporator and supplying the formed element to the load lock chamber, wherein all chambers are provided with an apparatus for manufacturing an organic light emitting device that is maintained in a vacuum state. to provide.

Hereinafter, the present invention will be described in detail.

The organic light emitting device according to the present invention is based on a two-layer structure having a hole transport layer made of organic material in ITO-glass and a light emitting layer (also having electron transport characteristics), and an electron transport electrode, and a host in the hole transport layer for stability. -Guest system was applied. In this case, indium, silver-magnesium, or the like may be used as the electron transport electrode in addition to aluminum and magnesium / aluminum.

In the light emitting device having such a structure, the hole transport layer to which the host-guest system is applied is a polymer material used as a host to form a thin film in which a vacuum-polymerized polyimide and a hole transport material are uniformly mixed. Is in the range of 200 to 300 Hz, and preferably 250 Hz.

In addition, the deposition rate of the dianhydride: diamine: hole transport material is preferably about 1: 1: 2.

As the hole transport material, N, N'-diphenyl-N, N'-bis (3-methylphenyl) -1,1'-diphenyl-4,4'-diamine (TPD), 4,4 'of the following structural formula , 4 "-tris (3-methylphenyl-phenylamino) triphenylamine (MTDATA), poly (9-vinylcarbazole), and the like, with TPD being preferred.

The polyimide thin film is obtained by depositing dianhydride and diamine in a vacuum to obtain polyamic acid, and heat treating the polyimide thin film to obtain a polyimide thin film. Representative examples of dianhydride and diamine used in the present invention are as follows, the structural formula is shown in Table 1 below.

Dianhydrides:

1,2,4,5-tetracarboxyl benzene dianhydride (PMDA);

3,4,3 ', 4'-benzophenone tetracarboxyl dianhydride (BTDA);

3,4,3 ', 4'-biphenyl tetracarboxy dianhydride (BPDA);

Terphenyl tetracarboxy dianhydride (TPDA);

2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride (6FDA);

1,1-bis (3,4-dicarboxyphenyl anhydride) -1-phenyl-2,2,2-trifluoroethane (3FDA); And

9,9-bis (trifluoromethyl) -2,3,6,7-xanthene tetracarboxyl dianhydride (6FCDA).

Diamine:

4,4'-diaminophenyl ether (ODA);

p-phenylene diamine (PDA);

2,2'-bis (4-diaminophenyl) hexafluoropropane (6FDAM);

1,1'-bis (4-aminophenyl) -1-phenyl-2,2,2-trifluoroethane (3FDAM);

2,2'-bis (trifluoromethyl) benzidine (TFMB); And

1,3-bis (3-aminophenoxy) benzene (APB).

The reaction of dianhydride and diamine in a vacuum state is shown in Reaction Scheme 1 below as a representative example of PMDA and ODA in a solid state.

In the above scheme, the anhydride end group of PMDA and the amino end group of ODA react to form an intermediate carboxylate, which is then a polyamic acid which is dehydrated by heating to produce a polyimide. The polyimide thin film thus prepared has a much higher density film state than that by chemical synthesis.

As a light emitting material having electron transport characteristics used in the present invention, tris (8-hydroxyquinolinato) aluminum (Alq ₃ ), 3- (4-biphenylyl) -4-phenyl-5- ( 4-t-butylphenyl) -1,2,4-triazole (TAZ), 2,5-bis (1-naphtolyl) -1,3,4-oxadiazole (BND), among others. Alq ₃ is preferred. In addition, the thickness of the light emitting layer composed of the light emitting material is in the range of 160 to 240 kPa, preferably 200 kPa.

In the present invention, the effects of the use of a hole transport material and a light emitting material having electron transport characteristics will be described with reference to the case of the typical compounds TPD and Alq ₃ as follows.

Referring to the electron band structure of the TPD and Alq ₃ shown in FIG. 2, electrons and holes injected during driving accumulate by potential barriers at the 2nd and 3rd interface, which is caused by the electron-hole coupling. The result of improving the luminescence property can be obtained. This is similar to the light emission phenomenon by PN junction in the light emitting diode using inorganic semiconductor and is the main point of low voltage driving.

In the present invention, the vacuum deposition polymerization reaction is carried out in the vacuum system shown in Figure 1 to proceed all the manufacturing process of the organic light emitting device in a vacuum state.

The vacuum system shown in FIG. 1 basically includes a load lock chamber (I), a preclean chamber (II), a deposition polymerization (VDP) chamber (III), an organic thin film manufacturing chamber (IV) using a diffusion cell, and a cathode. It consists of a cathode coating chamber (V) with an electron beam evaporator for producing a metal film to be used.

Referring to the manufacturing process of the organic light emitting device using the vacuum system of the present invention.

The pumping ports 4, 9, 19, 23, 27 maintain the entire vacuum system in a high vacuum. After breaking the vacuum of the load lock chamber I, the glass-ITO substrate is mounted to the substrate holder 3 through the quick access door 5. The chamber I is maintained at high vacuum through the pumping port 4 and then the gate valve 6 is opened and the ITO glass substrate is moved to the substrate holder 7 of the chamber II using the magnetic bar 1.

After moving the magnetic bar 1 to its original position, the gate valve 6 is closed and a pre-cleaning process is performed using the ion source 8. At this time, Ar, O ₂ , N ₂ and the like are used as the ion source 8.

After the process in the pre-clean chamber II is completed, the gate valves 6 and 10 are opened and the magnetic bars 1 are moved to the substrate holder 11 of the chamber III by using the magnetic bars 1 and then the magnetic bars 1. Is in place and the valves are closed.

In chamber (III), in order to form a thin film mixed with polyimide and a hole transport material (eg, TPD) on an ITO substrate, a thermal bath 12 containing dianhydride, diamine, and powder of a hole transport material on the ITO substrate is used. 13, 14) generates steam in the evaporation state of each material under a certain degree of vacuum. After maintaining a specific temperature of the substrate (eg PMDA: 185 ℃, ODA: 155 ℃), the mass flow valves (15, 16) are adjusted to deposit reactants on the substrate in a component ratio that can react with each other. The lead material and the diamine material undergo an acylation reaction to form a specific polyamic acid thin film and heat treatment to form a polyimide thin film. At this time, the vapor of the hole transport material is also uniformly distributed in the polyimide thin film by adjusting the mass flow valve 17.

After forming a polyimide thin film containing a hole transport material as a hole transport layer, an organic light emitting material coating chamber equipped with a diffusion cell 22 containing an electron transport layer material (for example, Alq ₃ ) powder, which plays an electron transport and emission role ( IV) by moving the substrate to deposit the organic material at a deposition rate of less than 0.3 Å / sec using precise temperature control.

After the organic thin film layer is completed, the gate valve 24 is opened and then moved to the substrate holder 25 using the magnetic bar 1 to form the electrode for the cathode. The cathode of the light emitting device is manufactured by depositing a specific metal using the electron beam evaporator 26.

After all processes are completed, the device manufactured in the chamber (I) is transferred through the gate valve, and then the gate valve is closed, and only the chamber (I) breaks the vacuum and pulls the device out.

In order to precisely adjust the composition ratio of each monomer during vacuum deposition polymerization of polyimide, a feedback process may be applied by precisely adjusting the mass flow valve and attaching a residual gas analyzer (RGA).

The organic light emitting device manufacturing apparatus of the present invention does not need to be exhausted except for repairing the inside of the vacuum system, so that it is possible to maintain a clean atmosphere and save time waiting for obtaining a desired degree of vacuum.

As shown in FIG. 3, the organic light emitting device manufactured according to the above-listed sequence includes a glass (a), an ITO layer (b), a hole transport layer (c), a light emitting layer (d) having electron transport characteristics, and a cathode (e). It has a rough structure consisting of).

The method and apparatus of the present invention can also be used for the development of various optoelectronic devices.

Hereinafter, the present invention will be described in more detail with reference to the following examples and comparative examples (see FIGS. 4, 5, 6, and 7). However, the scope of the present invention is not limited only to the following Examples.

Examples and Comparative Examples

Using the vacuum system of the present invention, an organic light emitting device was manufactured by the following method while changing the composition of the hole transport layer, the thickness of the hole transport layer and the light emitting layer, and the presence or absence of heat treatment, as shown in Table 2 below:

1) The ITO patterned in the desired form was washed and prepared.

2) PMDA, ODA and TPD were mounted in a crucible in the chamber about 0.05g each.

3) After the prepared ITO was mounted on the substrate holder in the chamber, the temperature of the crucible containing PMDA, ODA and TPD was heated to 180 ° C., 160 ° C. and 220 ° C. under vacuum of 2 × 10 ⁻⁶ Torr, respectively. .

4) When the temperature change of each crucible reaches ± 0.5 ℃, the deposition rate of PMDA: ODA: TPD is 0.1: 0.1: 0.1Åsec, 0.1: 0.1: 0.2Å with a thickness monitor (STM / 100MF). After confirming that / sec or 0.2: 0.2: 0.1 kPa / sec, the mass flow valve was opened to start deposition to prepare a thin film having a thickness of 450 or 525 kPa before the heat treatment.

5) The polyamic acid thin film thus formed was heated at 2 ° C. per minute and heat-treated at 200 ° C. for 1 hour to prepare a polyimide thin film having a thickness of 250 or 347 mm 3.

6) Alq ₃ and aluminum were deposited on the heat-treated thin film at 200 or 300 Å and 3,500 차례로, respectively, to fabricate an organic light emitting device.

The injection voltage and the light emission (turn-on) voltage of the organic light emitting device prepared above are also shown in Table 2.

Structural Formula of Representative Diamine Device number PMDA: ODA: TPD Hole Transport Layer Thickness Light emitting layer thickness Heat treatment Injection voltage (V) Light-emitting (turn-on) voltage (V) One 2: 2: 1 347 300 ○ 6.5 8.7 2 2: 2: 1 525 300 × 5.5 8.9 3 1: 1: 1 347 300 ○ 3.3 8.6 4 1: 1: 1 525 300 × 6.4 10.2 5 1: 1: 2 347 300 ○ 5.7 10.4 6 1: 1: 2 525 300 × 7.4 11.5 7 2: 2: 1 250 200 ○ 3.3 6.6 8 2: 2: 1 450 200 × 3.05 7.66 9 1: 1: 1 250 200 ○ 3.1 5.8 10 1: 1: 1 450 200 × 2.32 5.64 11 1: 1: 2 250 200 ○ - 5.7 12 1: 1: 2 450 200 × 3.45 6.28 13 2: 2: 1 250 300 ○ 7.05 8.17 14 1: 1: 1 250 300 ○ 5.57 7.05 15 1: 1: 2 250 300 ○ 4.05 6.54

Figure 4 shows the electroluminescence intensity curve (Fig. 4a, 4c, 4e and 4g) and the current density curve (Fig. 4b, 4d, 4f and 4h) according to the applied voltage of the organic light emitting device. 4A and 4B are comparisons between the heat treatment characteristics in the case where the hole transport layer is 250 mW and the light emitting layer is 300 mW (element number 1, 2, 3, 4, 5, 6). FIGS. 4C and 4D show the hole transport layer is 180 mW and the light emitting layer is 200 mW. Is a comparison between the heat treatment characteristics in the case of (device No. 7, 8, 9, 10, 11, 12), and FIGS. 4E and 4F show that the light emitting layer is 300 kPa and heat treated (device No. 1, 3, 5, 13, 14, 15). 4G and 4H are comparisons between the thickness characteristics of the light emitting layer in the case where the hole transport layer is 180 kPa and subjected to heat treatment (element number 7, 9, 11, 13, 14, 15).

5 shows an external quantum efficiency curve 5-1 and a light emission efficiency curve 5-2 according to the current density or applied voltage of the organic light emitting diode. 5A to 5F are comparisons between the thickness characteristics of the light emitting layer in the case where the hole transport layer is 180 kPa and subjected to heat treatment (element number 7, 9, 11, 13, 14, 15), and FIGS. 5G to 5L show the hole transport layer is 250 kPa and the light emitting layer is 300 kPa Is a comparison between the heat treatment characteristics in the case of (device No. 1, 2, 3, 4, 5, 6), and FIGS. 5M to 5R show that the hole transport layer is 180 mW and the light emitting layer is 200 mW (element number 7, 8, 9, 10, 11 and 12) is a comparison between the heat treatment characteristics.

FIG. 6 shows electroluminescent spectra according to a change in voltage of the organic light emitting diode. 6A to 6F are comparisons between the thickness characteristics of the light emitting layer when the hole transport layer is 180 GPa and heat treated (element number 7, 9, 11, 13, 14, 15), and FIGS. 6G to 6L are when the light emitting layer is 300 GPa and heat treated ( It is a comparison between the thickness characteristics of the hole transport layer of the device number 1, 3, 5, 13, 14, 15), Figures 6m to 6r is a case where the hole transport layer is 180 Å and the light emitting layer is 200 Å (element number 7, 8, 9, 10, 11 and 12) is a comparison between the heat treatment characteristics.

From the above results, the deposition rate of polyimide and TPD was 1: 1, and the organic light emitting device had excellent characteristics and the luminous efficiency was about 12 Lm / W in the case of heat treatment with the hole transport layer of 180Å and the light emitting layer of 200Å. It can be seen that high. The emission photo of the organic light-emitting device of this element No. 11 having optimum conditions (Fig. 7A, upper left, upper right, lower left and lower right: 6, 7, 8, and 9 V applied) 7A and 7B are shown in comparison with the emission picture of the light emitting device (Fig. 7B, top left, top right, bottom left and bottom: 8, 9, 10 and 11V applied).

In the present invention, by preparing a mixed layer consisting of a hole transport material and a polymer material by vacuum evaporation polymerization method, the hole transport layer can completely remove the contamination by solvent and foreign matter, and can produce a uniform and high density organic thin film layer at low voltage. It is possible to manufacture an organic light emitting device capable of driving, high stability and long life.

Claims (8)

In the method of manufacturing an organic light emitting device by vacuum deposition of a hole transport layer and a light emitting layer having electron transport characteristics on a glass-ITO electrode, the hole transport layer is vacuum-deposited polymerization of the hole transport material, dianhydride and diamine A method of manufacturing a low voltage driving organic light emitting diode, characterized in that the polyimide is formed into a uniform mixed thin film. The method of claim 1, Dianhydride is 1,2,4,5-tetracarboxylic benzene dianhydride (PMDA), 3,4,3 ', 4'-benzophenone tetracarboxylic dianhydride (BTDA), 3,4,3', 4'-biphenyl tetracarboxy dianhydride (BPDA), terphenyl tetracarboxy dianhydride (TPDA), 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride (6FDA), 1,1-bis (3,4-dicarboxyphenyl anhydride) -1-phenyl-2,2,2-trifluoroethane (3FDA) and 9,9-bis (trifluoromethyl) -2, 3,6,7-xanthene tetracarboxylic dianhydride (6FCDA). The method of claim 1, Diamine is 4,4'-diaminophenyl ether (ODA), p-phenylene diamine (PDA), 2,2'-bis (4-diaminophenyl) hexafluoropropane (6FDAM), 1,1'- Bis (4-aminophenyl) -1-phenyl-2,2,2-trifluoroethane (3FDAM), 2,2'-bis (trifluoromethyl) benzidine (TFMB) and 1,3-bis (3 -Aminophenoxy) benzene (APB). The method of claim 1, And the hole transport material is N, N'-diphenyl-N, N'-bis (3-methylphenyl) -1,1'-diphenyl-4,4'-diamine (TPD). The method of claim 1, A light emitting layer having electron transport characteristics is produced by vacuum-depositing tris (8-hydroxyquinolinato) aluminum (Alq ₃ ). The method of claim 1, And the thickness of the hole transport layer is in the range of 200 to 300 kPa, and the thickness of the light emitting layer is in the range of 160 to 240 kPa. The method of claim 1, And a deposition rate of dianhydride: diamine: hole transport material is 1: 1: 2. A load lock chamber through which a glass-ITO substrate is supplied and a finished device is discharged; An anode substrate cleaning chamber for cleaning the glass-ITO substrate supplied from the load lock chamber through an ion source; A deposition polymerization chamber for generating a mixed thin film of a polyimide formed by depositing and polymerizing a hole transport material, dianhydride and diamine on a pre-clean glass-ITO substrate supplied from the anode substrate cleaning chamber, and the deposition polymerization chamber An organic light emitting material coating chamber for depositing an organic light emitting material on a substrate supplied from the substrate; And a cathode coating chamber for coating the substrate supplied from the organic light emitting material coating chamber with an electron beam evaporator and supplying the formed element to the load lock chamber, wherein all chambers are kept in a vacuum state.