JPH01313892A - Image display device and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain a bright multi-color display of long lifetime operating on low voltage by constituting the display with airtight substrates sandwiching the luminous part of an organic material. CONSTITUTION:An electric field luminous part 3 comprising an organic phosphor material and the like is sandwiched between a rear substrate 1 and a transparent glass substrate 2. A stripe-shaped rear electrode 4 and a transparent electrode 5 are formed in directions approximately orthogonal with each other at the side of the rear substrate 1 and glass substrate 2 faced to the electric field luminous part 3. In other words, the region where electrodes intersect each other becomes each picture element and is sandwiched and sealed with two opposite insulation substrates. Consequently, an external atmosphere as a major deterioration cause, and in particular an adverse effect on an organic compound layer due to the adsorption of an oxygen or moisture can be eliminated. According to the aforesaid construction, the lifetime of elements can be substantially extended.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to image display devices such as thin displays.

BACKGROUND OF THE INVENTION In recent years, attempts have been made to develop electroluminescent devices using organic compounds as constituent materials. For example, Japanese Journal Φ of Applied Physics (Japanese Journal Φ of Applied Physics)
e Journal of Apphed Ph.
1slas) 27 (2) (1988), page L289, there is an electroluminescent device having a structure in which an organic phosphor layer and a charge transport layer are laminated. FIG. 5 shows its cross-sectional view. A semi-transparent lower electrode 51 made of AU is provided on a glass substrate 50, and a layer of N having a film thickness of 200'A is formed on the lower electrode 51.
N''-diphenyl-N, N''-(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine (
Hereinafter, it will be abbreviated as TPD. ), a hole transport layer 52 consisting of
A phosphor layer 53 and an electron transport layer 54 made of a perylene tetracarboxyl group derivative are constructed, both of which have a thickness of 1000 Å. The upper electrode 55 is made of a thin Mg film. A phthaloperinone derivative is used as the material for the organic phosphor layer 53, and bright electroluminescence is observed by applying an electrostatic field as shown in the figure (35th Applied Physics Complete Volume). Annual lecture). By selecting the material of the organic phosphor layer 53, the emission and wavelength can be changed.

Problems to be Solved by the Invention However, the conventional example described above has a problem in that the light emission deteriorates quickly. The luminescence half-life time in the conventional example was only about 5 hours when the applied voltage was 50 V, which was problematic for use as a display.

Means for Solving the Problems A light-emitting section composed of a light-emitting layer, an electrode, etc. containing at least an organic compound as all or a part of its constituent material is provided in the gap between a pair of airtight substrates, at least one of which is transparent. , an image display device having a structure sandwiched and sealed between both substrates is created.

Function The organic compound layer such as the organic electroluminescent layer described above is
It is sandwiched between two insulating substrates and sealed. Therefore, there is no adverse effect on the organic compound layer due to adsorption of external atmosphere, particularly oxygen or moisture, which is a major cause of deterioration. As a result, the life of the element is dramatically extended.

Example of implementation An embodiment of the present invention is shown in FIGS. 1 and 2.

FIG. 1 is a perspective view of an embodiment of the image display device of the present invention. This is an image display device using an electroluminescent element made of organic phosphor material. An electroluminescent section 3 made of an organic fluorescent material or the like is sandwiched between a back substrate 1 and a transparent glass substrate 2.

On the sides of the back substrate 1 and glass substrate 2 facing the electroluminescent section 3, striped back electrodes 4 and transparent electrodes 5 are formed in directions substantially perpendicular to each other. The area where the electrodes intersect each other becomes a picture element. , FIG. 2 is a sectional view of a picture element portion of the image display device of this embodiment.

In this embodiment, as shown in FIG.
Hereinafter, it will be abbreviated as an organic EL layer. ), a charge generation layer 7 and a charge transport layer 8 .

Between the back electrode 4 and the transparent electrode 5, a DC or pulsed bias voltage Vt of about several tens of volts is applied as shown in the figure.
Apply.

Due to the electric field applied to the electroluminescent section 3, electrons are injected from the transparent electrode 5 and holes from the back electrode 4 are injected into the organic EL layer 6, where they are radiatively recombined.Next, the structure and each material will be described. .

The rear substrate 1 is preferably an airtight insulator with a smooth surface or a metal plate whose surface is coated with an insulator, and is preferably made of a material with good thermal conductivity. In this example, a 1 mm thick glass plate with an A1 reflective film formed on the back surface was used. For the back electrode 4, an AI thin film formed in a stripe shape with a width of 180 μm and a pitch of 200 μm was used. This is Cr+ A u,
N IN W etc. may also be used.

The charge generation layer 7 includes P-type amorphous Sj+-xCx:
H alloy was used. A suitable film thickness is 1000 to 3000A. The material may be any photoreceptor material that has photosensitivity to the emission wavelength of the organic EL layer.

In addition, P-type amorphous Si1 amorphous C1
Inorganic photoreceptor materials such as Se-based alloys and organic photoreceptor materials such as polyvinyl carbazole compounds, phthalocyanine pigments, azo pigments, and azulenium salt compounds may be used. This is preferably a photoreceptor material with high dark resistance.

The charge transport layer 8 formed in contact with the charge generation layer 7 has high hole mobility, and the hole mobility from the charge generation layer 7 to the charge transport layer 8 is
It is also desirable that the material is a hole transporting material that can efficiently inject holes from the charge transport layer 8 to the organic EL layer 6. In this example, N,N'-diphenyl-N with the chemical structure shown below is used.
, N'-(3-methylphenyl)-1,1'-biphenyl-4,4''-diamine (hereinafter abbreviated as TPD) was used.

This is a smooth amorphous thin film of 500 to 200 OA.

For the organic EL layer 6, an appropriate organic phosphor material is selected depending on the emission wavelength. In this example, perylene (orange) is placed in each picture element corresponding to the 3" primary color.
Coronene (green) and anthracene (blue) were used. This may be, for example, a phthalobenilone derivative, a rhodamine B1 coumarin derivative, or a fluorescent dye such as a fluorescent metal chelate compound. The film thickness is 500 to 200 OA.

In this example, the transparent electrode 5 is an In-8n-0 thin film (I
TO) was used. Alternatively, ZnO or the like may be used. Like the back electrode 4, this is also formed in a stripe shape with a width of 180 μm and a pitch of 200 μm.

FIG. 3 is a diagram showing the structure of the electrodes and the electroluminescent section 3. As shown in FIG. (1) is a diagram showing the configuration of the first embodiment. In the configuration, other embodiments (2) to (5)
Shown below. (2) has a five-layer structure like (1), but
This is the case when the direction of the electric field is reversed.

In this case, the back electrode 4 (hereinafter abbreviated as BE) is
A MgAg alloy is used, and the charge generation layer 7 (hereinafter abbreviated as CGL) is made of N-type amorphous Si+-xC.
x: H alloy, amorphous Si:H1Se system, Cd5
1 Inorganic photoreceptor materials such as ZnO and amorphous CzSe alloys, and organic photoreceptor materials such as polyvinyl carbazole compounds, phthalocyanine pigments, azo pigments, and azulenium salt compounds are used. Charge transport layer 8 (hereinafter referred to as CTL
It is abbreviated as. ), for example, the following materials:
An electron transport layer such as a perylenetetracarboxyl group derivative (hereinafter abbreviated as Pv) is used.

Also, as in the embodiment (3), the organic EL layer 6 (hereinafter referred to as 1.
It is abbreviated as EL. ) may be sandwiched between CTL and CGL. In this example, the CTL has a TPD
For CGL, N-type amorphous Si+-xCx:
H alloy is used. In the embodiment (4), in the embodiment (1), a CTL layer made of Pv is provided between the CTL and the transparent electrode 5 (hereinafter abbreviated as TE).

The embodiment (5) has a configuration in which an N-type CGL and EL are sandwiched between a TE and a BE.

The electroluminescent element in the image display device of the present invention has Vt>
At about 45V, the light emission suddenly becomes stronger. This can be considered as follows. The electric field applied to the electroluminescent section 3 reaches a strength sufficient for charge injection at the interface of each layer,
It starts to emit light. Once it begins to glow, the resistance value of the charge generation layer 7 drops rapidly, and the electric field applied to other layers and interfaces becomes stronger. The light emission intensity is determined by the amount of current that can be injected in that electric field. This time, on the contrary, even if the applied voltage is reduced, the light continues to emit light, and suddenly disappears at about 40V. This is because the resistance of the charge generation layer 7 increases rapidly again.

The image display device of the present invention is actually driven by line sequential driving using striped back electrodes 4 and transparent electrodes 5 that are orthogonal to each other. At that time, the above-mentioned hysteresis characteristics are used to write, hold, and rewrite the image. That is, first, a DC sustain voltage of about 42V is applied to the back electrode 4. At the time of writing, the lighting voltage is applied to the back electrode 4 line by line (total voltage 50V). −
Once lit, the picture elements are kept lit for one frame period by the sustain voltage. When rewriting after one cycle, the negative erase voltage is superimposed (the total voltage is 35V).
) Write a new one again.

Next, a method for manufacturing an image display device according to the present invention will be explained based on the first embodiment.

After depositing an AI thin film on the glass rear substrate 1 on which an A1 reflective film has been formed on the back surface by a vapor deposition method, etc., a width of 180 μm and a pitch of 200 μm is formed by a photolithography method or the like.
A striped back electrode 4 is formed. On top of this, a P-type amorphous Si+-xCx:H alloy film is deposited with a thickness of about 1000 to 3000 A by sputtering or the like. T.P.
A charge transport layer 8 made of D is applied thereon by a vacuum evaporation method or the like.
It is formed as an amorphous thin film of about 500 to 2000A.

On the other hand, in the present case, first, a transparent electrode 5 made of ITO is formed on a glass substrate 2 by sputtering and photolithography in the same way as the back electrode 1, and then an organic EL layer 6 is formed on it by a vacuum evaporation method or the like. do. In these steps, it is not necessary to pattern the organic EL layer θ, the charge generation layer 7, and the charge transport layer 8.

Next, the back substrate with the film formed thereon and the glass substrate 2 are placed with their film-formed surfaces facing each other, and the periphery is bonded with epoxy resin or the like, and the charge transport layer 8 on the back substrate 1 side is bonded to the glass substrate 2.
The organic EL layer 6 on the glass substrate side is brought into close contact. The adhesive surface is 1. It does not have to be between the charge transport layer 8 and the organic EL layer, and may be between other films. When adhering, use one of the following three methods. That is, (a) a method of evacuating the inside to bring them into close contact; and (b) a method of comparing the softening point and melting point of the organic EL layer 6 and the charge transport layer 8, and comparing the softening point and melting point of the organic EL layer 6 and charge transport layer 8, (C) A method in which the material is heated and compressed at a temperature below its melting point, and (C) a method in which these two methods are used in combination.

First, the manufacturing method of (a) will be explained with reference to FIG.

As shown in (1), the back substrate 1 on which the film is formed and the glass substrate 2 are bonded together with an adhesive 10 such as epoxy resin on the periphery of the back substrate 1 with the film-formed surfaces facing each other. Next, as shown in (II), the exhaust hole 11 provided at the end is evacuated and sealed.

The charge axis, the feeding layer 8, and the EL layer 6 are brought into close contact with each other due to atmospheric pressure. By this method, it is possible to make the adhesive surface adhere to the adhesive surface without leaving any air bubbles or the like. (b) improves the adhesion of the films by compressing the organic film on the surface to be adhered in a softened state. This means that even if there are small irregularities on the surface,
It has the advantage that the entire surface can be completely adhered. In the case of this example in which TPD was used for the charge transport layer 8 and anthracene was used for the organic EL layer 6, the bonding was carried out under heating at 120°C to 180°C. (c) is a method in which the organic film on the bonding surface is softened after the two substrates are bonded in step (a) or during vacuum evacuation, so that the entire surface is completely adhered.

This combines the advantages of (a) and (b).

The above image display device of the present invention has a luminance of 50 fL.
It was possible to achieve a half-life of about 500 to 1000 hours. Moreover, the energy conversion efficiency is 0.
It was 5-0.8%.

The present invention has made it possible to realize a high-brightness multi-color display that has a long life and is stably driven at low voltage. In particular, the main point of the present invention is that the following significant effects can be obtained.

(1) First, in terms of luminescence intensity, the lifespan was conventionally about 5 hours, but with the present invention, it is about 500 to 100 hours.
It was 0 hours and I was so excited. This can be considered as follows. That is, by sandwiching the organic film layer between two opposing glass substrates and shielding it from the outside air, adsorption of gas molecules such as H20 and 02 to the organic film interface was reduced. Also, the entry of these molecules into the membrane was reduced. As a result, the amount of interface states and trapped centers within the film, which serve as non-radiative recombination centers, was reduced. Alternatively, it was also possible to suppress the increase in non-radiative recombination centers, which is thought to be caused by the current or the heat generated by it.

(2) Next, it became possible to apply a high voltage even if the film thickness of each layer was made thinner, making it possible to improve luminous efficiency and lower the driving voltage. For example, even in the first OA, 6
A voltage of 0 to 70V could be stably applied. As aforementioned,
A driving power supply of about 20 Vpp is sufficient for driving the panel. Therefore, compared to conventional inorganic EL elements that require a high-voltage driving power source, a significant cost reduction can be achieved. This is thought to be due to the following effects.

In other words, in the conventional method of laminating each layer in order, if there is a pinhole in the lower layer, if a conductive layer is deposited on top of it, the conductive layer will fill the inside of the pinhole. When a voltage is applied, the withstand voltage of the pinhole portion decreases, but in the manufacturing method of the present invention, even if there is a pinhole in the lower layer, the upper conductive layer does not penetrate into the pinhole, so the withstand voltage decreases. Does not decrease.

Effects of the Invention According to the present invention, a high-brightness multicolor display that has a long life and is driven stably at low voltage can be realized by having a structure in which a light emitting part made of an organic material is sandwiched between airtight substrates. I can do it.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the configuration of an embodiment of the image display device of the present invention, FIG. 2 is a sectional view of the same embodiment, and FIG. 3 is a diagram showing another configuration of the electroluminescent section of the present invention. FIG. 4 is a cross-sectional view showing an example of the method for manufacturing an image display device of the present invention, and FIG. 5 is a cross-sectional view showing an example of a conventional organic electroluminescent device. DESCRIPTION OF SYMBOLS 1... Back substrate, 2... Glass substrate, 3... Electroluminescent part, 4... Back electrode, 5... Transparent electrode, 6...
- Organic EL layer, 7... Charge generation layer, 8... Charge transport layer, 10... Adhesive, 11... Exhaust hole. Name of agent: Patent attorney Toshio Nakao and one other person

Claims (7)

[Claims] (1) In the gap between a pair of airtight substrates, at least one of which is transparent, a light-emitting section consisting of a light-emitting layer, an electrode, etc. containing at least an organic compound as all or part of its constituent material is placed between both substrates. An image display device characterized by having a sandwiched and sealed structure. (2) A face plate electrode plate in which a plurality of striped transparent electrodes and an organic electroluminescent layer are laminated on the surface of a glass substrate, and a back electrode plate in which a plurality of striped electrodes are provided on the surface of an insulating substrate are connected to both electrodes. It is characterized in that the striped electrodes provided on the plate are opposed to each other so as to be almost orthogonal, and the peripheral part is sealed, or the peripheral part is sealed in a vacuum, and the inside is evacuated and brought into contact with each other. Claim 1
The image display device described in . (3) A method for manufacturing an image display device according to claim 1, wherein at least the bottom layer of the laminated film consisting of a light-emitting layer, an electrode, etc. constituting the light-emitting part, or at least the entire laminated film is By pre-forming a predetermined number of layers, which are not layers, on the lower substrate in order from the bottom layer, and on the other hand, forming the remaining layers on the upper substrate in order from the top layer, the film-formed surfaces of both substrates are brought into close contact with each other. A method of manufacturing an image display device, comprising forming the light emitting section. (4) Of the laminated film consisting of the light-emitting layer, electrodes, etc. constituting the light-emitting part, at least the lowest layer, or at least a predetermined number of layers that are not all the laminated films, are placed on the lower substrate in order from the bottom layer, while the remaining layers are After forming the layers in advance on the upper substrate in order from the top, first sealing the periphery of the film-formed surfaces of both substrates, then evacuating the gap, or sealing the periphery in vacuum, 4. The method of manufacturing an image display device according to claim 3, wherein the films formed separately on both substrate surfaces are pressed together to complete the laminated film of the light emitting section. (5) A method for manufacturing an image display device according to claim 1, which comprises a step of heating when creating a laminated film consisting of a light-emitting layer, an electrode, etc. A method for manufacturing a display device. (6) Claim 4 or 5, which includes a step of heating during or after evacuation.
A method for manufacturing an image display device according to section 1. (7) The method for manufacturing an image display device according to claim 5 or 6, wherein the heating temperature is higher than the softening point and lower than the melting point of the organic compound constituting the light emitting part.