JP2002212548A - Organic el material, and surface emission device and displaying device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new organic EL material. SOLUTION: This organic EL material is represented by general formula 1 (wherein, A is a residue obtained by removing four or more hydrogens from an aromatic compound or a heterocyclic compound; X is an atomic group obtained by bonding two or more residues obtained by removing two or more hydrogens from benzene or obtained by removing two or more hydrogens from cyclohexane; Y is a residue obtained by removing two or more hydrogens from benzene, or an atomic group obtained by bonding two or more of the residues; and k, m and n are each an integer).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an organic EL material and a surface light emitting device and a display device using the same.

[0002]

2. Description of the Related Art As a backlight for a liquid crystal display device,
Generally, a cold cathode lamp is used. The cost of the backlight accounts for about 30% of the total cost of the liquid crystal display device, which is a factor of cost increase. Further, the cold cathode lamp has low luminous efficiency.

[0003] As a backlight device replacing the cold cathode lamp, an organic electroluminescence element (organic EL element) has attracted attention. Organic EL materials include monomer-based materials and polymer-based materials. Monomer EL materials
Generally, the film is formed by vacuum evaporation. The polymer EL material can be formed into a film by a coating method. For this reason, the latter is more advantageous in terms of manufacturing cost.

[0004]

Since a backlight using a polymer organic EL material can be driven at a low voltage, the power consumption of a liquid crystal display device can be reduced.
Further, cost reduction and size reduction can be achieved as compared with the case where a cold cathode lamp is used. However, an organic EL material that can withstand practical use has not been developed.

An object of the present invention is to provide a new organic EL material. Another object of the present invention is to provide a light emitting device and a display device using the organic EL material.

[0006]

According to one aspect of the present invention, the general formula (4)

[0007]

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(A is a residue obtained by removing at least four hydrogen atoms from an aromatic compound or a heterocyclic compound,
X is an atomic group to which at least two groups selected from the group consisting of a residue obtained by removing at least two hydrogen atoms from benzene and a residue obtained by removing at least two hydrogen atoms from cyclohexane are bonded; Or a residue obtained by removing at least two hydrogen atoms from benzene or a residue obtained by bonding at least two residues obtained by removing at least two hydrogen atoms from benzene, and k, m, and n are integers. ) Is provided.

According to another aspect of the present invention, a transparent substrate,
A transparent conductive film covering one surface of the transparent substrate, an alignment film formed on the surface of the transparent conductive film and aligning liquid crystal molecules in a specific direction, and formed on the alignment film surface; There is provided a surface light emitting device having a light emitting layer made of an organic material represented by (4) and an electrode layer formed on a surface of the light emitting layer.

According to another aspect of the present invention, a transparent substrate,
A transparent conductive film covering one first surface of the transparent substrate;
An alignment film formed on the surface of the transparent conductive film and aligning a liquid crystal material in a specific direction; a light emitting layer formed on the alignment film surface and made of an organic material represented by the general formula (4); An electrode layer formed on the surface of the light emitting layer; and a liquid crystal layer disposed on a second surface of the transparent substrate opposite to the first surface, the light transmitting layer propagating in the thickness direction. Said liquid crystal layer capable of controlling the rotation angle of linearly polarized light,
A polarizing plate disposed on the liquid crystal layer and having a polarization axis orthogonal to the alignment direction of the alignment film.

The side chain of the oxadiazole containing a residue from which two hydrogen atoms have been removed has liquid crystal properties. When the side chain is oriented in one direction, light polarized in a direction parallel to the orientation direction is emitted. Therefore, it is not necessary to arrange a polarizing plate between the light emitting layer and the liquid crystal layer. Thereby, the utilization efficiency of the emitted light can be increased.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An organic EL material according to an embodiment of the present invention has a general formula (5)

[0013]

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## EQU1 ## The main chain is composed of a repeating unit composed of a residue obtained by removing four hydrogen atoms from benzene and a vinylene group. 2 on the benzene ring constituting the main chain
The side chains of the book are attached. One side chain has 1 m of carbon atoms.
Is a valent ether group. Here, m is an integer satisfying 5 ≦ m ≦ 15. l is an integer such that the molecular weight is 100,000 to 5,000,000.

Next, the chemical structure of the other side chain will be described. In the benzene ring constituting the main chain, an alkylenedioxy group having n carbon atoms, a biphenylylene group, a residue obtained by removing two hydrogen atoms from oxadiazole, a phenylene group, and a monovalent ether group having k + 1 carbon atoms are They are connected in series in order. This side chain portion has liquid crystal properties. Here, n is an integer satisfying 5 ≦ n ≦ 15,
k is an integer satisfying 5 ≦ k ≦ 15. When k, m, and n are too small, the compound represented by the general formula (5) becomes difficult to dissolve in the organic solvent. On the other hand, if k, m, and n are too large, it becomes difficult to synthesize the compound.

Next, a method for synthesizing the above-mentioned organic EL material will be described. The following general formula (6)

[0017]

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A benzene derivative represented by the formula is prepared. Furthermore, the general formula (7)

[0019]

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An oxadiazole derivative represented by the following formula is prepared.

A benzene derivative represented by the general formula (6) is mixed with an oxadiazole derivative represented by the general formula (7), and potassium hydroxide is added. General formula (8)

[0022]

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The compound represented by the formula is obtained. Furthermore, K
OC (CH ₃ ) ₃ is added to cause a polymerization reaction. Thereby, the organic EL material represented by the general formula (5) is synthesized.

FIG. 1 is a sectional view of a liquid crystal display device using an organic EL material according to an embodiment. This liquid crystal display device
Backlight panel 1, liquid crystal panel 10, and polarizing plate 2
0 is included.

The backlight panel 1 has a laminated structure in which a transparent substrate 2, a transparent electrode 3, an alignment film 4, a light emitting layer 5, and an electrode 6 are laminated in this order. The transparent electrode 3 is formed of indium tin oxide (ITO) and has a thickness of about 200 nm. The ITO film is formed by sputtering.

The alignment film 4 is formed of a mixture of poly 3,4-ethylenedioxythiophene (PEDOT) and polystyrene sulfonate (PSS). The alignment film 4 is formed by a spin coating method, and has a thickness of about 200 nm. The surface of the alignment film 4 is subjected to a rubbing treatment. Note that polyanline or the like may be used as an alignment film material.

Next, a method for forming the light emitting layer 5 will be described. A solution obtained by dissolving the organic EL material represented by the above general formula (5) in an organic solvent such as toluene or chloroform is
Spin coating is performed on the surface of the alignment film 4. After the application, the substrate is heated to a temperature equal to or higher than the liquid crystalization temperature of the organic EL material and then cooled to room temperature. When the temperature becomes equal to or higher than the liquid crystalization temperature, the side chain portion containing oxadiazole of the organic EL material represented by the general formula (5) is oriented so as to be parallel to the rubbing direction of the orientation film 4. When cooled to room temperature to form a solid phase,
This alignment state is maintained without being affected by an external electric field or the like.

The electrode 6 is made of an AlLi alloy and has a thickness of about 3
It is a conductive film of 00 nm. The AlLi alloy film is formed by, for example, vacuum evaporation.

The liquid crystal panel 10 is of an active matrix type using, for example, a thin film transistor (TFT). Since the TFT type liquid crystal panel has a well-known structure, an outline of the structure will be briefly described here. TFT
On the opposing surface of the side transparent substrate 11, the transparent pixel electrodes 14 arranged in a matrix are formed. Transparent counter substrate 12
Are disposed substantially parallel to the TFT-side transparent substrate 11 so as to face the pixel electrodes 14. On the opposing surface of the opposing substrate 12, a transparent common electrode 15 is formed. A liquid crystal layer containing a liquid crystal material is sandwiched between the TFT-side transparent substrate 11 and the counter substrate 12. Although not shown in FIG. 1, an alignment film, a TFT, a black matrix, and the like are additionally formed. By applying a voltage between the pixel electrode 14 and the common electrode 15, the rotation angle of the linearly polarized light propagating through the liquid crystal layer 13 in the thickness direction can be controlled.

The TFT-side transparent substrate 11 is in close contact with the transparent substrate 2 of the backlight panel 1. The polarizing plate 20 is in close contact with the outer surface of the counter substrate 12. When viewed along a direction perpendicular to the substrate surface, the polarization axis of the polarizing plate 20 is orthogonal to the rubbing direction of the alignment film 4.

Next, the operation principle of the liquid crystal display device shown in FIG. 1 will be described. When a DC voltage is applied to both electrodes so that the electrode 6 becomes a negative electrode and the transparent electrode 3 becomes a positive electrode and carriers are injected into the light emitting layer 5, polarized light is emitted from the light emitting layer 5 to the liquid crystal panel 10 side. . The polarization direction of the emitted light is parallel to the direction in which the side chain containing oxadiazole of the general formula (5) is oriented, that is, the rubbing direction of the orientation film 4.

If the polarization direction does not rotate when passing through the liquid crystal panel 10, the polarized light does not pass through the polarizing plate 20, and a black display state is obtained. When the polarization direction turns by 90 degrees, the polarized light transmits through the polarizing plate 20, and a white display state is obtained. If the turning angle is between 0 and 90 degrees,
A halftone display state is obtained.

In the liquid crystal display device shown in FIG. 1, polarized light is emitted from the backlight panel 1. Therefore, it is not necessary to dispose a polarizing plate between the backlight panel 1 and the liquid crystal panel 10. Thereby, the utilization efficiency of the emitted light can be increased. In addition, power consumption can be reduced and the size can be reduced as compared with the case where a cold cathode lamp is used.

In the above example, the biphenylene group was bonded to the carbon atom on the main chain side of the oxadiazole of the general formula (5). The biphenylene group may be replaced by an atomic group in which two or more phenylene groups and cyclohexylene groups are bonded in total. Formula (9) shows a case where the biphenylene group is replaced with an atomic group in which a phenylene group and a cyclohexylene group are bonded one by one.

[0035]

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Formula (10) shows a case where the biphenylene group is replaced by an atomic group in which two phenylene groups and one cyclohexylene group are bonded in a chain.

[0037]

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Further, in the above-described embodiment, the case where one phenylene group is bonded to the carbon atom at the tip of the side chain of the oxadiazole of the general formula (5) is shown. This one phenylene group may be replaced by an atomic group in which two or more phenylene groups are bonded in a chain.

In the above embodiment, the case where the main chain of the organic EL material contains a benzene ring has been described. May be included. Examples of the condensed polycyclic hydrocarbon include naphthalene and anthracene. Examples of the heterocyclic compound include pyrrole, thiophene, furan and the like.
Examples of the fused heterocyclic compound include carbazole and fluorene.

The present invention has been described in connection with the preferred embodiments.
The present invention is not limited to these. For example, it will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

[0041]

As described above, according to the present invention,
By using an organic EL material containing oxadiazole in a side chain, polarized light can be emitted. When this is applied to the backlight panel of a liquid crystal display device,
Since there is no need to dispose a polarizing plate between the liquid crystal panel and the backlight panel, light use efficiency can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view of a liquid crystal display according to an embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 backlight panel 2 transparent substrate 3 transparent electrode 4 alignment film 5 light emitting layer 6 electrode 10 liquid crystal panel 11 TFT side transparent substrate 12 opposing substrate 13 liquid crystal layer 14 pixel electrode 15 common electrode 20 polarizing plate

Claims (7)

[Claims] (1) a first general formula: (A is a residue obtained by removing at least four hydrogen atoms from an aromatic compound or a heterocyclic compound, and X is a residue obtained by removing at least two hydrogen atoms from benzene and at least two hydrogen atoms from cyclohexane. Y is a residue obtained by removing at least two hydrogen atoms from benzene, or a residue obtained by removing at least two hydrogen atoms from benzene. Is an atomic group in which at least two are bonded, and k, m, and n are integers.) 2. The method according to claim 1, wherein n in the first general formula is 5 ≦ n ≦ 1.
The organic EL material according to claim 1, wherein k is an integer that satisfies 5 ≦ k ≦ 15. 3. The compound according to claim 1, wherein A in the first general formula is a residue obtained by removing four hydrogen atoms from benzene.
2. The organic EL material according to item 1. 4. The organic EL material according to claim 1, wherein X in the first general formula includes a biphenylene group or an atomic group in which a phenylene group and a cyclohexylene group are bonded. 5. The organic EL material according to claim 1, wherein Y in the first general formula is a phenylene group. 6. A transparent substrate, a transparent conductive film covering one surface of the transparent substrate, an alignment film formed on the surface of the transparent conductive film and aligning liquid crystal molecules in a specific direction, and the alignment film. Formed on the surface and has the general formula (A is a residue obtained by removing at least four hydrogen atoms from an aromatic compound or a heterocyclic compound, and X is a residue obtained by removing at least two hydrogen atoms from benzene and at least two hydrogen atoms from cyclohexane. Y is a residue obtained by removing at least two hydrogen atoms from benzene, or a residue obtained by removing at least two hydrogen atoms from benzene. Is an atomic group in which at least two are bonded, and k, m, and n are integers.) And a surface having an electrode layer formed on the surface of the light-emitting layer. Light emitting device. 7. A transparent substrate, a transparent conductive film covering one first surface of the transparent substrate, and an alignment film formed on the surface of the transparent conductive film and aligning a liquid crystal material in a specific direction; Formed on the surface of the alignment film, and represented by the general formula: (A is a residue obtained by removing at least four hydrogen atoms from an aromatic compound or a heterocyclic compound, and X is a residue obtained by removing at least two hydrogen atoms from benzene and at least two hydrogen atoms from cyclohexane. Y is a residue obtained by removing at least two hydrogen atoms from benzene, or a residue obtained by removing at least two hydrogen atoms from benzene. Is an atomic group in which at least two are bonded, and k, m, and n are integers.), An electrode layer formed on the surface of the light emitting layer, and the transparent A liquid crystal layer disposed on a second surface of the substrate opposite to the first surface, the liquid crystal layer being capable of controlling a turning angle of linearly polarized light propagating in a thickness direction of the liquid crystal layer. And crystal layer, wherein disposed on the liquid crystal layer, display device having a polarizing plate having a polarization axis orthogonal to the alignment direction of the alignment layer.