JPH04202394A - Organic luminescent element, production thereof and optically neural network using the same element - Google Patents

Abstract

PURPOSE:To obtain an organic luminescent element having high luminance and low change of luminescent brightness with time by laminating a specific polymer to a substrate by a vapor-liquid interface developing film-forming method. CONSTITUTION:A polymer having a repeating unit shown by the formula [n>=2; X is O, S, Se or Te; Y is (substituted) aromatic group; Z is imide ring-containing group] is laminated to a face of substrate such as glass to give the objective luminescent element. The luminescent element is useful for a light arithmetic unit or a space light-modulating element such as luminous type display.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a light-emitting device such as a spatial light modulation device used in an optical processing device or a light-emitting display, a method for manufacturing the same, and an optical neural network device using the same. It is related to.

[Prior Art] In recent years, attempts have been made to develop organic light emitting devices using organic compounds as constituent materials. For example, Japanese Journal of Applied Physics,
nese Journal of Applied Ph.
1sics) 27 (2) (1988), page L269, there is an electroluminescent device having a structure in which an organic light-emitting layer and a charge transport layer are laminated. Transparent A on a glass substrate
A lower electrode made of u is provided, and on top of that, N,N'-diphenyl-N,N with a film thickness of 2000A (angstrom) is provided.
'-(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine (hereinafter abbreviated as TPD), and a hole transport layer of 1000A in thickness.
An organic light emitting layer and an electron transport layer made of a perylene tetracarboxyl group derivative are configured. The upper electrode is made of a Mg thin film. Bright electroluminescence has been observed when a phthaloperinone derivative is used as the material for the organic light-emitting layer and an electrostatic field is applied (35th Annual Conference on Applied Physics).

By selecting the material of the organic light emitting layer, the emission wavelength can be changed.

[Problems to be Solved by the Invention] By stacking a charge transport layer and a light emitting layer, charge injection from an electrode is increased and luminous efficiency is dramatically improved compared to conventional organic light emitting devices. The luminous efficiency is low at 0.5% or less, and improvement is required.

In addition, the luminance of the emitted light changes greatly over time, which causes problems, particularly the reduction in charge injection efficiency into the light emitting layer and the accumulation of space charges in the charge transport layer.

The following factors are thought to be responsible for the decrease in luminance.

■ Molecules forming the light-emitting layer crystallize and quench light.

■ The molecules that make the light-emitting layer resistant to acid undergo a chemical reaction with oxygen molecules and decompose.

■ Charge is accumulated in the film, and charge injection from the outside is inhibited.

In order to solve the problems of the prior art, it is an object of the present invention to provide an organic light-emitting device with high brightness and little change in luminance over time, a method for manufacturing the same, and an optical neural network device using the light-emitting device. .

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

-Z-(-X-Y-) -(A) (However, n≧2 X: 0. Any one of S, Se, or Te Y: Aromatic or substituted aromatic group Z: Group containing an imide ring) In the above structure, it is preferable that the polymer represented by the general formula (A) is laminated with 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 deposition method.

Further, the optical neural network device of the present invention is an optical neural network device that includes a lower electrode on a substrate, and a light-receiving layer, a light-emitting layer, a charge transport layer, and a transparent electrode are sequentially laminated on the lower electrode, and the light-emitting layer is It is characterized by having a layer containing a polymer containing a repeating unit represented by the general formula (A).

[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 included as a light-emitting layer, the light-emitting layer is formed within the main chain skeleton of the heat-resistant polymer. Or the general formula (A) is incorporated into the side chain and is a light emitting part.
The Z groups are dispersed at the molecular level and do not form aggregates with each other. As a result, an organic light-emitting element with high luminance and little change in luminance over time can be obtained. Furthermore, there is a low possibility that the host polymer will melt and crystallize due to Joule heat caused by the current flowing through the film. Furthermore, Y in general formula (A)
The group has excellent charge transport ability in the membrane.

Therefore, charge accumulation in the film is small.

Further, 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, the 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 interfacial deposition method, a thin and defect-free film can be obtained. I can do it. The light emitting portion of the light emitting layer is limited to the vicinity of the interface with the electrode or other charge transport layer. Therefore, it is advantageous for the light-emitting layer to be thin enough to prevent pinholes from occurring. It is also advantageous in terms of lowering the driving voltage. Preferably, by laminating a polymer of general formula (A) on a substrate surface by the Langmuir-Prodgett method (LB method), a polymer layer with a thickness of several atomic layers and without pinholes can be obtained.

Further, there is provided an optical neural network device according to the present invention, 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 laminated thereon, wherein the light-emitting layer has the general formula (A ) According to the structure of the optical neural network element having a layer containing a polymer containing the repeating unit shown in ( ), it is possible to make the element capable of accurate recognition.

[Examples] Examples of the present invention will be described with reference to the drawings.

FIG. 1 shows a sectional view of an embodiment of the organic light emitting device of the present invention. The structure of the device is such that a transparent insulating substrate 101 (for example, glass) i and a transparent conductive electrode 102 (for example, I To, S
n OX ), and an organic light-emitting layer 103 is stacked thereon.

Next, an upper electrode 104 is provided thereon. A direct current or alternating current electric field is applied as an external voltage between the transparent conductive electrode 102 and the upper electrode 104. The thickness of the organic light emitting layer 103 is 5
It is preferable that it is in the range of A to 5000A.

FIG. 2 shows a sectional view of an embodiment of the organic light emitting device of the present invention. The device has a transparent conductive electrode 202 (for example, ITo, 5nO) on a transparent insulating substrate 201 (for example, glass).
x), in which a charge transport layer 203 and an organic light emitting layer 204 are laminated. Next, an upper electrode 205 is provided thereon. A direct current or alternating current electric field is applied as an external voltage between the transparent conductive electrode 202 and the upper electrode 205. 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 preferably in the range of 100 A to 5 μm.

FIG. 3 shows a cross-sectional view of an embodiment in which the element has an organic light-receiving layer. A lower electrode 302 is provided on an insulating substrate 301, and a light receiving layer 303 and an organic light emitting layer 304 are laminated thereon. Furthermore, a charge transport layer 305 is laminated to form a transparent electrode 306.
will be established. The lower electrode may be a transparent conductive electrode.

A direct current or alternating current electric field is applied as an external voltage between the transparent conductive electrode 306 and the lower electrode 306.

When the organic light-receiving layer 303 receives light emitted from the organic light-emitting layer 304, the device becomes a light-emitting element with memory characteristics.

Further, by using the lower electrode 302 as a transparent conductive electrode, light is irradiated from the outside through the lower electrode 302, and the organic light-receiving layer 30
3, it becomes a light-emitting spatial light modulator. Furthermore, by combining both functions, it becomes a spatial light modulator having memory properties.

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

O0 In the above formula, the preferred range of m is 1O-1o, oo
It is o. As for Ar, for example, in the formula A2 shown below, n is preferably in the range of 1 to 5.

Representative examples of the light-emitting moiety X group in general formula (A) include perylene (orange), coronene (green), and anthracene (blue), corresponding to the three primary colors. In addition, the following are mentioned as examples of aromatics or substituted aromatics. anthracene, naphthalene, pyrene, perylene, naphthacene, benzanthracene, benzophenanthrene,
These include fused polycyclic hydrocarbons and substituted derivatives thereof such as chrysene, triphenylene, and phenanthrene, and fused polycyclic quinones and substituted derivatives thereof such as anthraquinone, dibenzopyrenequinone, anthanthrone, isoviolanthrone, and pyranthrone.

Typical examples of the Y group in general formula (A) include:

Examples of the Z group in general formula (A) are as follows.

Example 1 In the organic light emitting device shown in FIG.
A glass substrate is used as 1, and a transparent conductive electrode 1 is attached to this.
As No. 02, an ITO film having a thickness of 0.1 to 0.5 μm is formed by sputtering. As the organic light-emitting layer 103, a polymer A2 having anthracene as a light-emitting portion was formed.

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

A schematic diagram of the LB method accumulator used for film formation is shown in FIG. In FIG. 4, 401 is an LB device, 402 is a pure water developing liquid tank, 403 is a substrate, and 404 is a weight.

A diamine compound having anthracene as a light emitting moiety and pyromellitic anhydride of aromatic tetracarboxylic dianhydride;
is added to an organic solvent dimethylacetamide in a ratio of 1:1 to polymerize polyamic acid.

This polyamic acid is dimethylacetamide, benzene 1
: Dilute to 1 mmol/L with a mixed solvent of 1. On the other hand, LB
To apply the method, polyamic acids are salt-formed with long-chain alkyl amines. i.e. N, N-dimethyl-n
-Hexadecylamine (hereinafter referred to as C16DMA) was dissolved in a mixed solvent of dimethylacetamide and benzene 1:1.
Adjust to mmol/L. Polyamic acid: C16DC16D: Adjusted to 2 immediately before being developed at the air-water interface using the LB method,
Develop on the surface of pure water. The cumulative conditions of the polyamic acid monomolecular film in the LB method were a surface pressure of 25 dyn/cm, a pulling rate of 3 to 10 mm/min, and a room temperature of 20°C. 2
0 layers are developed, and the thickness of the laminated film is set to 100A (angstroms). Finally, the imidization of the polyamic acid cumulative film is
By chemical imidization method. The substrate is immersed in a mixed solution of acetic anhydride:pyridine:benzene=1:l:3 for 12 hours to form a polyimide cumulative film. Thereafter, the solvent is removed by washing with benzene.

The electrical characteristics and light emitting characteristics of this device were investigated. A DC voltage is applied between the transparent conductive electrode 102 and the upper electrode 104.

Its voltage-current characteristics are shown in FIG. 5, and its current-emission brightness characteristics are shown in FIG. When the applied DC voltage is 5V or more, the current density is 10
It becomes 0mA/car or more. At this time, the luminance is 100
At the beginning of exceeding cd/n (at an applied voltage of 10 V, approximately 5
A luminance of 00 cd/i was obtained.

In addition to anthracene, naphthalene, pyrene, and perylene were used as the base for the light-emitting part. The emission spectrum at an applied voltage of 10 cm is shown in FIG.

Example 2 In the organic light emitting device shown in FIG.
A glass substrate is used as a substrate, and a transparent conductive electrode 20 is attached to this.
2, a charge transport layer 203 is formed by forming an ITO film with a thickness of 0.1 to 0.5 μm by sputtering. As the material for the charge transport layer 203, polyimide (hereinafter referred to as BPDA-n) polymerized from benzophenone tetracarboxylic dianhydride (hereinafter referred to as BPDA) and oligoparaphenylene sulfide diamine was used. Synthesis of polyamic acid, which is a precursor of polyimide, is carried out using BPDA and oligoparaphenylene sulfide diamine in a solvent dimethylacetamide. This polyamic acid is applied to the surface of the substrate using a spinner in an amount of 500A to 200OA. After coating, the substrate is placed in a heat treatment furnace and heat treated at 300° C. for 2 hours. In this process, the polyimide film is imidized and crystallized. As the organic light-emitting layer 204, a 5-atomic layer of polymer A2 was formed in the same manner as in Example 1.

The electrical characteristics and light emitting characteristics of this device were investigated. A DC voltage is applied between the transparent conductive electrode 202 and the upper electrode 205.

Its voltage-current characteristics are shown in FIG. 8, and its current-emission brightness characteristics are shown in FIG. When the applied DC voltage is 7V or more, the current density is 10
It becomes 0mA/cnf or more. At this time, the luminance is 100
cd/m, and at an applied voltage of 10 V, approximately 50
Emission brightness of 'Ocd/rri was obtained.

Example 3 A light-emitting element having memory characteristics using polyimide in the organic light-receiving layer was manufactured. The device structure is shown in FIG. BPD was formed as a light-receiving layer 303 by the method of Example 2 on a glass substrate 301 on which ITO was formed as a lower electrode 302.
A-2 is deposited to a thickness of 2 μm. The light-emitting layer contains polymer A2. containing anthracene having a peak emission wavelength of 480 nm and naphthalene having a peak emission wavelength of 460 nm. Al was used. The wavelength is shorter than the sensitivity range of 550 nm of BPDA-Ph3. The transparent electrode 206 was formed by forming an ITO film at room temperature.

The applied voltage-emission brightness characteristics are shown in FIG. The luminescence characteristics have history characteristics. After entering the light emitting state by applying 40V,
The light emitting state is maintained until the applied voltage is set to 20V or less.

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

This image display device was able to achieve a half-life of more than 1000 hours when the luminance was 50 fL. Moreover, the energy conversion efficiency was 1°0 to 3.3%. According to this example, it was possible to realize a high-brightness multi-color display that has a long life and is driven stably at low voltage.

Example 5 A light-emitting spatial light modulator was manufactured. The element structure is the same as in Example 3. In this case, the light-receiving layer 3.3 is optically written by light incident on the glass substrate 301. The incident light was a semiconductor laser (780% m). Example 3 A polyimide film BPDA-2 containing 2% by weight of metal-free phthalocyanine was used as a light-receiving layer sensitive to this wavelength.
The film was formed using almost the same method. The light emitting layer 304 is Example 3
Polymer A2 having an emission peak at 480 nm was used in the same manner as above. FIG. 11 shows the change in luminance of light emission with respect to the intensity of incident light. Nonlinear characteristics and memorability occur. That is, the portion that has been optically written into a light-emitting state continues to emit light even after the incident light disappears.

When the incident light is irradiated with an applied voltage of 35 V, the light receiving layer 3
03, the voltage drops and the electric field concentrates on the light-emitting layer 304, resulting in a light-emitting state. Even in the absence of incident light, the light-receiving layer maintains a low resistance state due to irradiation from the light-emitting layer, and light emission continues. When the applied voltage becomes less than 5V, the light becomes quenched, and the original 35
Even if the light-receiving layer 203 returns to the v state, the light-receiving layer 203 has a high resistance, so extinction continues.

We constructed an optical neural network using this organic light-emitting device and confirmed its functionality.

Figure 12 shows the configuration. The orthogonal learning method is used and consists of an incident image 111 using the light emitting device of Example 1, a microlens array 112, a learning mask pattern 113, and a light threshold chain element 114 using the organic light emitting device of this example. The input image 111 displays 10 alphabetic characters in a 6×6 matrix. Image input uses memory and writes electrically to each pixel. Learning mask pattern 11
3 is a film consisting of a 36×36 matrix, and the transmittance is changed so that the 8-gradation display determined by the orthogonal learning method can be expressed by the transmitted light intensity. Optical threshold chain element 114
is a 6×6 matrix, and transmitted light from 6×6 mask patterns is focused on each pixel by a microlens array 113. Light is emitted based on the optical nonlinear characteristics shown in FIG.

Using this system, a 100% recognition rate was obtained 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 explained above, according to the embodiments of the present invention, an image display device using an organic light-emitting element having a polymer of general formula (A) as a light-emitting layer has a long life and is stably driven at a low voltage. We were able to realize a high-brightness display. We also created a spatial light modulator that can be optically written by external light irradiation. This was ideal for the configuration of optical computing systems such as optical neural network systems.

[Effects of the Invention] As explained above, according to the present invention, since the light-emitting layer includes a layer containing a polymer containing a repeating unit represented by the general formula (A), the luminance is high and the luminance does not change over time. The number of organic light emitting elements can be reduced.

Further, 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, the 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 interfacial deposition method, a thin and defect-free film can be obtained. I can do it.

Further, there is provided an optical neural network device according to the present invention, 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 laminated thereon, wherein the light-emitting layer has the general formula (A ) According to the structure of the optical neural network element having a layer containing a polymer containing the repeating unit shown in ( ), it is possible to make the element capable of accurate recognition.

[Brief explanation of the drawing]

1, 2, and 3 are cross-sectional views of one embodiment of the organic light-emitting device of the present invention, and FIG. Figure 5 shows Example 1.
Figure 6 shows the voltage-current characteristics of an organic light-emitting device in
The figure shows the current luminescence brightness characteristics of the organic light emitting device in Example 1, FIG. 7 shows the emission spectrum of the organic light emitting device, and FIG. 8 shows the current luminance characteristics of the organic light emitting device in Example 2. 9 is a diagram showing the voltage luminance luminance characteristics of the organic light emitting device in Example 3, and FIG. 10 is a diagram showing the memory characteristics of the organic light emitting device in Example 3.
FIG. 11 is a diagram showing the change in luminance of the organic light emitting device according to the incident light intensity in Example 5, and FIG.
FIG. 1 is a schematic diagram of an optical neural network system in FIG. 101...Glass substrate, 102...Transparent electrode, 10
3... Light emitting layer, 104... Upper electrode, 111...
Input image, 112... Microlens array, 123
... Learning mask pattern, 124 ... Optical threshold characteristic, 201 ... Glass substrate, 202 ... Transparent electrode,
203...Charge transport layer, 204...Light emitting layer, 205
... Upper electrode, 206 ... Organic light emitting element, 301.
... Substrate, 302 ... Lower electrode, 303 ... Light-receiving layer, 304 ... Light-emitting layer, 305 ... Charge transport layer, 30
6... Transparent electrode, 307... Charge transport layer, 401.
...LB device, 402...Pure water developing liquid tank, 403...
・Substrate, 404゛...load. Name of agent: Patent attorney Hiroyuki Ikeuchi and one other person V) Figure 5 Current density (mA/aI) Figure 6 Figure 7 Figure 8 Current density (mA/c# Figure 9 Current density (mA/can) Figure 10

Claims (4)

[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-(-X-Y-)_n-(A) (However, n≧2 X: Any of O, S, Se, Te Y: Aromatic or substituted aromatic group Z: Group containing an imide ring ) (2) The organic light-emitting device according to claim 1, wherein the polymer represented by the general formula (A) is laminated with another light-receiving layer. (3) A method for manufacturing an organic light-emitting device, in which a polymer containing a repeating unit represented by the general formula (A) is laminated on a substrate surface by a gas-liquid interfacial deposition method. -Z-(-X-Y-)_n-(A) (However, n≧2 X: Any of O, S, Se, Te Y: Aromatic or substituted aromatic group Z: Group containing an imide ring ) (4) An optical neural network device comprising a lower electrode on a substrate, and a light-receiving layer, a light-emitting layer, a charge transport layer, and a transparent electrode successively laminated thereon, wherein the light-emitting layer has the following general formula (A). An optical neural network device comprising a layer containing a polymer containing a repeating unit represented by: -Z-(-X-Y-)_n-(A) (However, n≧2 X: Any of O, S, Se, Te Y: Aromatic or substituted aromatic group Z: Group containing an imide ring )