JP2708274B2 - Organic light emitting device and method of manufacturing the same - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting device such as a spatial light modulator used for an optical operation device or a light emitting display and a method for manufacturing the same.

[Prior Art] In recent years, attempts have been reported for an organic light emitting device using an organic compound as a constituent material. For example, Japanese Journal of Applied Physics. (Japanese J
ounal of Applied Phisics) 27 (2) (1988), page L269, an electroluminescent device having a structure in which an organic light emitting layer and a charge transporting layer are laminated. Translucent on glass substrate
A lower electrode made of Au was provided, and a 2000A (angstrom) film of N, N'-diphenyl-N, N '-(3-methylphenyl) -1,1'-biphenyl-4,4'- A hole transport layer made of a diamine (hereinafter abbreviated as TPD),
In each case, an organic light emitting layer and an electron transporting layer composed of a perylene tetracarboxyl group derivative having a thickness of 1000 A are formed. The upper electrode is made of a Mg thin film. Bright electroluminescence has been observed when a phthaloperinone derivative is used as the material of the organic light emitting layer and an electrostatic field is applied (35th JSAP Spring Meeting). The emission wavelength can be changed by selecting the material of the organic light emitting layer.

[Problems to be Solved by the Invention] By laminating the charge transport layer and the light emitting layer, the charge injection from the electrode is increased and the luminous efficiency is remarkably improved as compared with the conventional organic light emitting device. The luminous efficiency is as low as 0.5% or less and needs improvement. In addition, the change of the light emission luminance with time is large, and in particular, there is a problem that the charge injection efficiency to the light emitting layer is reduced and the space charge is accumulated in the charge transport layer.

 The following factors are considered for the reduction of the light emission luminance.

The molecules forming the light emitting layer are crystallized and quenched.

The molecules forming the light emitting layer are decomposed by a chemical reaction with oxygen molecules or the like.

Electric charges are accumulated in the film, and external charge injection is inhibited.

SUMMARY OF THE INVENTION An object of the present invention is to provide an organic light emitting device having high luminance and little change in light emission luminance with time, and a method of manufacturing the same, in order to solve the problems of the conventional technology.

[Means for Solving the Problems] To achieve the above object, the organic light emitting device of the present invention comprises:
It has a layer containing a polymer containing a repeating unit represented by the following general formula (A) as a light emitting layer.

-Z-(-YX-) _n- (A) (however, n ≧ 2 X: any of O, S, Se, Te Y: aromatic or substituted aromatic group Z: group containing imide ring) In the structure, it is preferable that the polymer represented by the general formula (A) is laminated on another light receiving layer.

Further, in the method of the present invention, a polymer containing a repeating unit represented by the general formula (A) is laminated on a substrate surface by a gas-liquid interface developing film forming method.

The organic light emitting device of the present invention can be applied to an optical neural network device in which a lower electrode is provided on a substrate, and a light receiving layer, a light emitting layer, a charge transport layer, and a transparent electrode are sequentially stacked thereon. In this case, a layer containing a polymer containing a repeating unit represented by the general formula (A) is used for the light emitting layer.

[Function] According to the configuration of the present invention, since the layer containing the polymer containing the repeating unit represented by the general formula (A) is provided as the light emitting layer, the light emitting layer is formed in the main chain skeleton of the heat resistant polymer. Alternatively, the Z group of the general formula (A), which is incorporated in a side chain and is a light emitting portion, is dispersed at a molecular level and does not form an aggregate with each other. As a result, an organic light-emitting device having high luminance and little change in emission luminance with time can be obtained. Further, the possibility that the base polymer is melted and crystallized by Joule heat caused by the current flowing in the film is low. Furthermore, the Y group of the general formula (A) has excellent charge transport ability in the film. Therefore, charge accumulation in the film is small.

According to a preferred configuration of the present invention in which the polymer represented by the general formula (A) is laminated with another light-receiving layer,
Luminous efficiency can be further increased.

Further, according to the method of the present invention in which a polymer containing a repeating unit represented by the general formula (A) is laminated on a substrate surface by a gas-liquid interface developing film forming method, a thin film having no defects can be obtained. Can be. The light emitting portion of the light emitting layer is limited to the vicinity of the interface with the electrode or another charge transport layer. Therefore, it is advantageous for the light emitting layer to be thin so as not to generate pinholes. It is also advantageous in terms of lowering the driving voltage. Particularly preferably, when the polymer of the general formula (A) is laminated on the substrate surface by the Langmuir-Blodgett method (LB method), a polymer layer without pinholes with a thickness of several atomic layers can be obtained.

The present invention also provides an optical neural network device comprising a substrate, on which a lower electrode is provided, on which a light receiving layer, a light emitting layer, a charge transport layer, and a transparent electrode are sequentially laminated, wherein the light emitting layer has the general formula (A) According to the configuration of the optical neural network element having a layer containing a polymer containing a repeating unit shown in (1), an element capable of accurate recognition can be obtained.

Example An example of the present invention will be described with reference to the drawings.

FIG. 1 shows a sectional view of one embodiment of the organic light emitting device of the present invention. The device has a structure in which a transparent conductive electrode 102 (for example, ITO or SnO _x ) is provided on a transparent insulating substrate 101 (for example, glass), and an organic light emitting layer 103 is laminated. Next, top electrode 1
04 is provided. A DC or AC electric field is applied between the transparent conductive electrode 102 and the upper electrode 104 as an external voltage. The thickness of the organic light emitting layer 103 is preferably in the range of 5A to 5000A.

FIG. 2 shows a sectional view of one embodiment of the organic light emitting device of the present invention. Configuration of the device, a transparent insulating substrate 201 (e.g. glass) transparent conductive electrode 202 (e.g. ITO, SnO _X) on has, laminated charge transport layer 203 and the organic light emitting layer 204. Next, an upper electrode 205 is provided thereon. A DC or AC electric field is applied between the transparent conductive electrode 202 and the upper electrode 205 as an external voltage. A charge transport layer may be provided between the organic light emitting layer 204 and the upper electrode 205. The thickness of the charge transport layer 203 is 100A to 5μ.
The range of m is preferred.

FIG. 3 is a cross-sectional view of one embodiment having an organic light-receiving layer as the element configuration. Lower electrode 3 on insulating substrate 301
02 is provided, and the light receiving layer 303 and the organic light emitting layer 304 are laminated. Further, a charge transport layer 305 is laminated, and a transparent electrode 306 is provided. The lower electrode may be a transparent conductive electrode. Transparent conductive electrode 30
A DC or AC electric field is applied between 6 and the lower electrode 306 as an external voltage.

When light emitted from the organic light emitting layer 304 is received by the organic light receiving layer 303, the light emitting element has memory characteristics. When the lower electrode 302 is a transparent conductive electrode and light is irradiated from the outside through the lower electrode 302 and the light is received by the organic light receiving layer 303, the light emitting type spatial light modulator is used. Further, by combining both, a spatial light modulator having a memory property is obtained.

Examples of the polymer represented by the general formula (A) of the present invention include the following.

In the above formula, a preferable range of m is 10 to 10,000. Examples of Ar include those shown below.

In the formula A2, n is preferably in the range of 1 to 5.

Typical examples of the light emitting unit X group in the general formula (A) include perylene (orange), coronene (green), and anthracene (blue) corresponding to the three primary colors. The following are examples of the aromatic or substituted aromatic. Condensed polycyclic hydrocarbons such as anthracene, naphthalene, pyrene, perylene, naphthacene, benzoanthracene, benzophenanthrene, chrysene, triphenylene, phenanthrene and substituted derivatives thereof, anthraquinone,
Condensed polycyclic quinones such as dibenzopyrenequinone, anthantrone, isoviolanthrone, and pyranthrone; and substituted derivatives thereof.

As a representative example of the Y group in the general formula (A), Is mentioned.

 Examples of the Z group in the general formula (A) include the following.

Example 1 In the organic light emitting device shown in FIG.
A glass substrate is used as a transparent conductive electrode 102
Is formed to a thickness of 0.1 to 0.5 μm by sputtering. As the organic light-emitting layer 103, a polymer A2 having anthracene as a light-emitting portion was formed.

Next, spin coating or the like can be used as the film forming method, but the LB method was used as an example of the gas-liquid interface film forming method. Less than,
The procedure for forming a film by the LB method will be described.

FIG. 4 shows a schematic view of the accumulator of the LB method used for film formation. In FIG. 4, reference numeral 401 denotes an LB device, 402 denotes a pure water developing liquid tank, 403 denotes a substrate, and 404 denotes a weight.

A polyamic acid is polymerized by adding a diamine compound having anthracene as a light emitting portion and pyromellitic anhydride of an aromatic tetracarboxylic dianhydride in a ratio of 1: 1 to an organic solvent dimethylacetamide. This polyamic acid is diluted to 1 mmol / L with a mixed solvent of dimethylacetamide and benzene 1: 1. On the other hand, in order to apply the LB method, polyamic acid is subjected to salt formation with a long-chain alkylamine. That is, N, N−
Dimethyl-n-hexadecylamine (hereinafter referred to as C16DMA) is adjusted to 1 mmol / L with a mixed solvent of dimethylacetamide and benzene 1: 1. Immediately before being developed at the air-water interface by the LB method, the polyamic acid: C16DMA is adjusted to 1: 2 and developed on the pure water surface. The conditions for accumulating a polyamic acid monolayer in the LB method are as follows: surface pressure 25 dyn / cm, pulling speed 3-10 mm / min, room temperature
20 ° C. 20 layers are developed and the thickness of the laminated film is set to 100A (angstrom). Finally, imidation of the polyamic acid accumulation film is performed by a chemical imidization method. The substrate was immersed in a mixture of acetic anhydride: pyridine: benzene = 1: 1: 3 for 12 hours,
It is a polyimide accumulation film. After that, the solvent is removed by washing with benzene.

The electrical characteristics and light emission characteristics of this device were examined. A DC voltage is applied between the transparent conductive electrode 102 and the upper electrode 104. FIG. 5 shows the voltage-current characteristics, and FIG.
Shown in the figure. Current density is 100mA / cm ² at applied DC voltage of 5V or more
That is all. Emission luminance at this time is initially exceed 100 cd / m ^2,
At an applied voltage of 10 v, a light emission luminance of about 500 cd / m ² was obtained.

In addition, naphthalene, pyrene, and perylene were formed as a film of the light emitting part in addition to anthracene. The emission spectrum at an applied voltage of 10 V is shown in FIG.

Example 2 In the organic light emitting device of FIG.
A glass substrate is used as the transparent conductive electrode 202
The charge transport layer 203 is formed by depositing ITO having a thickness of 0.1 to 0.5 μm by a sputtering method. The material of the charge transport layer 203 is benzophenonetetracarboxylic dianhydride (hereinafter
Called BPDA. ) And a polyimide polymerized from oligoparaphenylene sulfide diamine (hereinafter referred to as BPDA-n). The synthesis of polyamic acid, which is a precursor of polyimide, is performed by using BPDA and oligoparaphenylene sulfide diamine in a solvent dimethylacetamide. 500A ~ 2000A of this polyamic acid on the substrate surface by spinner
Apply within the range. After coating, place the substrate in a heat treatment furnace and
A heat treatment is performed at 0 ° C. for 2 hours. In this process, the polyimide film is imidized and crystallized. As the organic light emitting layer 204, a five-atom layer of polymer A2 was formed in the same manner as in Example 1.

The electrical characteristics and light emission characteristics of this device were examined. A DC voltage is applied between the transparent conductive electrode 202 and the upper electrode 205. The voltage-current characteristics are shown in FIG. 8, and the current-emission luminance characteristics are shown in FIG.
Shown in the figure. Current density is 100 mA / cm ² at applied DC voltage of 7 V or more
That is all. Emission luminance at this time is initially exceed 100 cd / m ^2,
At an applied voltage of 10 v, a light emission luminance of about 500 cd / m ² was obtained.

Example 3 A light emitting device having a memory characteristic using polyimide for an organic light receiving layer was manufactured. The element structure is as shown in FIG. Glass substrate 301 with ITO formed as lower electrode 302
BPDA-2 is 2 μm thick on the light receiving layer 303 by the method of the second embodiment.
Form a film. For the light emitting layer, polymers A2 and A1 containing anthracene having an emission peak wavelength at 480 nm and naphthalene having an emission peak wavelength at 460 nm were used. Sensitivity range of BPDA-Ph3 5
The wavelength is shorter than 50 nm. As the transparent electrode 206, ITO was formed at room temperature.

FIG. 10 shows the applied voltage-emission luminance characteristics. The light emission characteristic has a hysteresis characteristic. After shifting to the light emitting state by applying 40 v, the light emitting state is maintained until the applied voltage is set to 20 v or less.

Example 4 In the organic light emitting device structure of Example 2, A2 having anthracene as blue in the light emitting layer and A of pyrene as green were used.
4. A full-color display was produced by developing the three primary colors of perylene A3 as red.

This image display device was able to achieve 1000 hours or more in half-life at a light emission luminance of 50 fL. The energy conversion efficiency was 1.0 to 3.3%. According to this embodiment, a long-life, high-brightness multi-color display that can be driven stably at a low voltage can be realized.

Example 5 A light-emitting spatial light modulator was manufactured. The element structure is the same as that of the third embodiment. In this case, the light receiving layer 303 is a glass substrate 3
Optical writing is performed by light incident from 01. The incident light was a semiconductor laser (780 nm). 2% by weight of metal-free phthalocyanine as a light-receiving layer sensitive to this wavelength
A polyimide film BPDA-2 to be contained was formed in substantially the same manner as in Example 3. The light emitting layer 304 is 480 in the same manner as in the third embodiment.
Polymer A2 having an emission peak at nm was used. FIG. 11 shows the change in emission luminance with respect to the incident light intensity. Non-linear characteristics and memory properties occur. In other words, the portion which has been light-written and turned into a light-emitting state maintains light emission even after the incident light has disappeared. When the incident light is irradiated with the applied voltage of 35 V, the voltage of the light receiving layer 303 drops, and the electric field concentrates on the light emitting layer 304, so that the light emitting layer 304 enters a light emitting state.
Even if there is no incident light, the light receiving layer maintains a low resistance state by irradiation from the light emitting layer, and light emission continues. The extinction state occurs when the applied voltage becomes 5 V or less, and the extinction state continues even after returning to the original 35 V state because the light receiving layer 203 has a high resistance.

An optical neural network was constructed using this organic light emitting device, and its functional operation was confirmed. FIG. 12 shows the configuration. The orthogonal learning method is used, and includes an incident image 111 using the light emitting element of the first embodiment, a microlens array 112, a learning mask pattern 113, and a light threshold element 114 using an organic light emitting element of the present embodiment. The input image 111 displays 10 letters of the alphabet in a 6 × 6 matrix. The image input uses a memory property and is electrically written to each pixel. The learning mask pattern 113 is formed of a 36 × 36 matrix, and is a film whose transmittance is changed so that 8-gradation display obtained by the orthogonal learning method can be expressed by transmitted light intensity. The light threshold element 114 is a 6 × 6 matrix, and transmitted light from 6 × 6 mask patterns is condensed on each pixel by the microlens array 113. Light is emitted according to the optical nonlinear characteristic shown in FIG. Using this system, 100% recognition rate was used for self-recall of a complete pattern of 10 letters of the alphabet and association of an incomplete pattern with a Hamming distance of 1.

As described above, according to the embodiment of the present invention, an image display device using an organic light-emitting element having a polymer represented by the general formula (A) as a light-emitting layer can be stably driven at a low voltage with a long service life. A high-brightness display was realized. Also, a spatial light modulator capable of optically writing by external light irradiation was obtained. This was optimal for constituent devices of an optical computing system represented by an optical neural network system.

[Effects of the Invention] As described above, according to the present invention, the general formula (A)
Since a layer containing a polymer containing a repeating unit represented by the formula (1) is provided as a light-emitting layer, an organic light-emitting element having high luminance and little change in luminance over time can be obtained.

According to a preferred configuration of the present invention in which the polymer represented by the general formula (A) is laminated with another light-receiving layer,
Luminous efficiency can be further increased.

Further, according to the method of the present invention in which a polymer containing a repeating unit represented by the general formula (A) is laminated on a substrate surface by a gas-liquid interface developing film forming method, a thin film having no defects can be obtained. Can be.

The present invention also provides an optical neural network device comprising a substrate, on which a lower electrode is provided, on which a light receiving layer, a light emitting layer, a charge transport layer, and a transparent electrode are sequentially laminated, wherein the light emitting layer has the general formula (A) According to the configuration of the optical neural network element having a layer containing a polymer containing a repeating unit shown in (1), an element capable of accurate recognition can be obtained.

[Brief description of the drawings]

1, 2 and 3 are cross-sectional views of one embodiment of the organic light-emitting device of the present invention. FIG. 4 is a schematic diagram of an accumulator of the LB method used for manufacturing the organic light-emitting device of the present invention. FIG. 5 is a diagram showing a voltage-current characteristic of the organic light emitting device in Example 1, FIG. 6 is a diagram showing a current light emission luminance characteristic of the organic light emitting device in Example 1, and FIG. 7 is an emission spectrum of the organic light emitting device. FIG. 8, FIG. 8 is a diagram showing current light emission luminance characteristics of the organic light emitting device in Example 2, FIG. 9 is a diagram showing voltage light emission luminance characteristics of the organic light emitting device in Example 3, and FIG. 3 is a diagram showing the memory characteristics of the organic light emitting device in FIG.
FIG. 11 is a diagram showing a change in light emission luminance with respect to the intensity of incident light of the organic light emitting element in the fifth embodiment. FIG. 12 is a schematic diagram of an optical neural network system in the fifth embodiment. 101: glass substrate, 102: transparent electrode, 103: light emitting layer, 104: upper electrode, 111: input image, 112: microlens array, 123: learning mask pattern, 124 ...
... Light threshold characteristics, 201 ... Glass substrate, 202 ... Transparent electrode, 203 ... Charge transport layer, 204 ... Emitting layer, 205 ... Top electrode, 206 ... Organic light emitting device, 301 ... Substrate, 302 lower electrode, 303 light receiving layer, 304 light emitting layer, 305 charge transport layer, 306 transparent electrode, 307 charge transport layer, 401
… LB device, 402… Pure water developing liquid tank, 403 …… Substrate, 404…
... weighted.

Claims (3)

(57) [Claims] 1. An organic light-emitting device having, as a light-emitting layer, a layer containing a polymer containing a repeating unit represented by the following general formula (A). -Z-(-YX-) _n- (A) (However, n ≧ 2 X: any of O, S, Se, Te Y: aromatic or substituted aromatic group Z: group containing imide ring) 2. The organic light emitting device according to claim 1, wherein the polymer represented by the general formula (A) is laminated on another light receiving layer. 3. A method for producing an organic light-emitting device, wherein a polymer containing a repeating unit represented by the general formula (A) is laminated on a substrate surface by a gas-liquid interface development film forming method. -Z-(-YX-) _n- (A) (However, n ≧ 2 X: any of O, S, Se, Te Y: aromatic or substituted aromatic group Z: group containing imide ring)