JPH088146B2 - Color EL display device and manufacturing method thereof - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin color EL display device, and more particularly to an EL display device capable of color display of three primary colors with high emission brightness and excellent color purity.

2. Description of the Related Art In recent years, a thin EL display device has been actively researched as a flat display device used for a computer terminal or the like. Among them, the development of color EL display devices influences the positioning as a display in the future, and therefore the most power is being focused on at present.

A color EL display using a color filter has already been proposed. However, some challenges remain. One of them is that the brightness of EL light is attenuated by about 40% when an organic color filter is used. On the other hand, the organic filter, which has the advantage that the transmittance of EL light is at least 90% or more, has a large film thickness and
When the EL layers were laminated, the step between the filter and the substrate was too large, which caused manufacturing problems such as disconnection.

As the configuration of the color EL display device, light emitted from a zinc sulfide phosphor layer having samarium as a light emitting impurity or a calcium sulfide phosphor layer having europium as a light emitting impurity is used for red light, and terbium is used as a light emitting impurity for green light. The three primary colors are emitted by using the light emission from the zinc sulfide phosphor layer that emits cerium and the calcium sulfide phosphor layer that emits cerium as blue light, and the emission from the strontium sulfide phosphor layer that uses cerium as the emission impurity for blue light. ing. (See Japanese Patent Laid-Open No. 61-260594) Problem to be Solved by the Invention A color EL display having a structure in which an EL layer is laminated on a conventional inorganic filter is manufactured stably because the filter is too thick. Can not do it.

Further, when a color EL display device is formed using conventional techniques, for example, europium-added calcium sulfide, terbium-added zinc sulfide, and cerium-added strontium sulfide for red, green, and blue, respectively, blue color purity and three primary colors High-quality color EL because the balance of emission brightness is not optimal and color reproducibility is insufficient.
The display device could not be realized. An object of the present invention is to provide a combination of a thin film structure and a filter for constructing a color EL display device having significantly higher brightness and wider color reproducibility and excellent display quality as compared with the conventional one which solves the above problems. That is.

Means for Solving the Problems A plurality of types of color filters are selectively provided on a translucent substrate, and a plurality of types of EL light emitting layers are provided on the color filters or on the color filters and in the gaps between the color filters. A back electrode is provided on top of the dielectric layer provided in the gap between the light emitting layers, and the color filter and the EL light emitting layer are made to correspond to each other.

Effects According to the above configuration, by combining the EL light emitting layer and the color filter, it is possible to realize a color EL display device having high brightness and wide color reproducibility, and moreover, the dielectric layer provided in the gap between the EL light emitting layers. Thereby, it is possible to prevent disconnection due to the step between the filter and the substrate.

Example A zinc sulfide phosphor containing divalent manganese ions as a luminescent impurity has a very high luminous efficiency of 2 to 8 lm / W, and has a broad emission spectrum with a center wavelength of 590 nm. Therefore, an appropriate filter is used. By this, color purity,
Bright red color can be realized. Zinc sulfide phosphor with trivalent terbium ion as a luminescent impurity emits blue component with a central wavelength of 490 nm, green component around 550 nm, and 590 n.
It is composed of wavelength components near n and 620 nm, and among them, the emission around 550 nm is the strongest and shows green emission with excellent color purity. Also, because the luminous efficiency is high, by using a filter,
It is possible to realize a green color with higher purity. Emission of strontium sulfide with trivalent cerium ion as luminescent impurity is 480n
Since it is a green-blue broad emission with m as the center wavelength, blue with high color purity can be realized by using an appropriate filter.

The present invention uses the following configurations in order to enable the configuration in which the phosphor and the filter are combined.

A sectional view for explaining one embodiment of a color EL display device of the present invention is shown in the drawing. The color filter 2 is selectively formed on the glass substrate 1. In this embodiment, the red filter 2A and the blue filter 2C are formed without forming the green filter.

After the color filter 2 is formed, the filter is not altered or the filter film is not cracked during the step of forming the film 8 from the film 3 and the annealing treatment of the formed EL light emitting layer 5. In addition, a heat resistant filter is required. Therefore, at the current level of technology, organic filters cannot be used.

In consideration of spectral characteristics such as light transmittance and heat resistance, one of preferable materials is an inorganic interference filter. For example, TiO ₂ having a refractive index of 2.20, SiO ₂ with a refractive index of 1.47, a refractive index of 1.62
Al ₂ O ₃ thin films are alternately laminated using an electron beam evaporation method.

However, for example, when forming a green filter (not shown), a 75 nm thick TiO ₂ film and a 113 nm thick SiO ₂ film are used.
It becomes necessary to stack layers. At this time, the total thickness is about
It will be 1.8 μm. In order to make the transmission characteristics steeper, it is necessary to increase the number of stacked layers. Therefore, when a thin film is laminated on this filter, the film thickness becomes thin or cut at the step portion. The transparent electrode 3 and the back surface 8 which constitute the matrix type EL display must necessarily intersect with each other, but the back electrode 8 is disconnected at the step portion of the filter for the reason described above.

In order to solve this problem, it is essential to form the dielectric layer 7 in the gap portion of the EL light emitting layer to reduce the step. As shown in the figure, the thickness of 2A and 2C cannot often be the same. The transparent electrode 3 is an indium (ITO) thin film added with tin and having a thickness of 200 nm formed by a sputtering method. The ITO thin film was processed using the photolithography technique to form the stripe-shaped transparent electrodes 3.
Then, a SrTiO ₃ ceramic target was subjected to high frequency sputtering in an argon atmosphere containing 10% oxygen to form a lower dielectric thin film 4 having a thickness of 500 nm.

On the lower dielectric thin film 4, a ZnS calcination containing 1 mol% of terbium fluoride (TbF ₃ ) was performed at a substrate temperature of 250 ° C. in an argon atmosphere containing 5% of hydrogen sulfide at a pressure of 1 × 10 ^-2 Torr. High-frequency sputtering was performed using the aggregate as a target to form a phosphor film of ZnS: Tb, F having a thickness of 500 nm. After that, a stripe-shaped green light emitting layer 5B was formed by using a photolithography technique, and heat treatment was performed at 500 ° C. for 1 hour in vacuum. A phosphor film made of ZnS: Mn and having a thickness of 600 nm is formed thereon by an electron beam heating vacuum evaporation method, and a striped red light emitting layer 5A is formed by using a photolithography technique. The heat treatment was performed at 1 ° C. for 1 hour. Furthermore, a phosphor film made of SrS: Ce, F having a thickness of 600 nm was formed on the layer by an electron beam heating vacuum deposition method,
A striped blue light emitting layer 5C was formed by using a photolithography technique, and then heat treatment was performed at 500 ° C. for 1 hour in vacuum.

Thickness of 200n on the light emitting layers 5A, 5B, 5C by electron beam evaporation
The upper dielectric thin film 6 made of yttrium oxide (Y ₂ O ₃ ) of m, the dielectric layer 7 provided in the gap between the EL light emitting layer 5, and the thickness 20.
Striped back electrodes 8 of 0 nm Al were sequentially formed.

On one surface of the transparent substrate 1 made of glass, a striped red filter 2A for blocking light having a wavelength shorter than 600 nm and a striped bandpass filter 2C for transmitting only blue light are formed. The striped red filter 2A and the blue filter 2C were arranged so as to correspond to the striped red light emitting layer 5A and the blue light emitting layer 5C, respectively.

By applying an AC voltage between the striped back electrode 8 and the striped transparent electrode 3 of the color EL display device of the present invention, the light emitting layer at the intersection of these electrodes can be made to emit light. By transmitting the optical substrate 1, a color image could be displayed using the three primary colors of red, green and blue. In the examples, a bandpass filter that transmits only blue light was used as the blue filter, but the same effect was obtained by using a long wavelength cut filter. Further, although no filter was used for greenness, better color reproducibility could be realized by using an appropriate bandpass filter.

 The second embodiment of the present invention will be described below.

As the color filter 2, an inorganic filter using a semiconductor basic absorption edge can be used instead of the filter using the interference effect of light used in the first embodiment. For example, a Zn _x Cd _1-x S film or a Zn _x Cd film with a film thickness of about 0.8 μm or more
_The half-value wavelength can be controlled by controlling the composition ratio of the _{1-x Sy} Se _1-y film. For example, when the composition ratio x of the Zn _x Cd _1-x S film formed by the resistance heating vapor deposition method was changed from 0.02 to 0.08, the half value wavelength of the filter could be changed within the range of 493 to 503 nm.

The method for manufacturing the EL display device of the present invention will be described below.

Patterning of the color filters 2A and 2C is performed by reactive sputter etching. Techniques related to such color filters are described in, for example, the Institute of Electronics and Communication Engineers Research Committee materials (ED-445, IPD42-16; pages 37 to 41; 1979) and National Technical Report (National Technical Rep.
ort), Vol. 28; pages 127-136; 1982). In order to effectively perform this dry etching, an Al ₂ O ₃ thin film is provided as an etching stopper layer between the glass substrate 1 and the color filter 2. (Not shown) After the color filter 2A is selectively installed,
An Al ₂ O ₃ thin film is provided (not shown), and the color filter 2C is selectively provided as in the case of 2A. Al ₂ O _{3 at} this time
The thin film is for protecting the color filter 2A.

The dielectric layer 7 is formed by using a polyimide polymer material, preferably a photosensitive polyimide material. A multilayer wire technology using a polyimide polymer material as an interlayer insulating film has already been developed. For example, electronic materials (p. 58-65; 1985 7)
Monthly issue) and IEICE Transactions (Vol.J68-C, page 1)
060-1065; 1985). In the figure, after forming the upper dielectric thin film 6, a photosensitive polyimide resin (for example, photosensitive polyimide: manufactured by Siemens, having a film thickness of about 1 to 2 μm) is formed on the entire surface by a spin coating method.
UR-3100: Toray, photosensitive polyimide: Hitachi-Hitachi Chemical) is formed (not shown). After this, exposure and development are performed to selectively remove the portions above the EL light emitting layers 5A, 5B, 5C (corresponding to the state before the back electrode 8 is formed in the figure). The development was performed by an ultrasonic wave immersion method using a developer containing dimethylacetamide as a main component (for example, DV-140 manufactured by Toray Industries, Inc.). After development, it was rinsed with isopropropyl alcohol and dried. In the present invention, when the upper dielectric thin film 6 or the upper dielectric thin film 6 is not provided, the EL light emitting layers 5A, 5B and 5C serve as stopper layers for etching the dielectric layer 7. Therefore, the polyimide resin layer above the EL light emitting layers 5A, 5B, 5C can be surely removed. Removal of the polyimide resin layer is done by N-methyl-2-pyridone or O ₂
It can also be removed by gas plasma. Use of reactive ion etching facilitates control of the taper angle of the through hole. Therefore, as shown in the figure, the distance between the transparent electrode 3 and the back electrode can be kept the same. The feature of this material is that it can be easily flattened without being affected by the irregularities of the underlying layer, and that it can easily be made thicker.
In addition, the residual stress is small regardless of the film thickness, and is also very close to the linear expansion coefficient of Al, which is the back electrode. A feature of the present invention is that the polyimide resin layer having no photosensitivity (for example, PIQ: Hitachi Chemical, PYRALIN PL-254
5 and PI-2555: made by DuPont), but it is not lost, but it goes without saying that a photosensitive resin layer must be newly provided on the polyimide resin layer when forming the pattern shown in the figure. Nor. (See, for example, JP-A-60-182134) When the dielectric layer 7 is a laminated film of an inorganic insulating film and a polyimide resin layer, the effect of the present invention is exhibited. Further, if the back electrode 8 is made of a superconducting material, external light reflection on the Al electrode surface is eliminated, and the electrical resistance value is also reduced, which is of great practical value.

EFFECTS OF THE INVENTION According to the present invention, a high-luminance, high-quality color EL display device having excellent color reproducibility can be provided, which is of great practical value.

[Brief description of drawings]

The drawing shows a cross-sectional view of a color EL display device for explaining one embodiment of the present invention. 1 ... Glass substrate, 2 ... Color filter, 3 ... Transparent electrode, 4 ... Lower dielectric thin film, 5 ... EL light emitting layer, 6 ...
Upper dielectric thin film, 7 ... Dielectric layer, 8 ... Back electrode.

Claims (4)

[Claims] 1. A plurality of types of color filters are selectively provided on a translucent substrate, and a plurality of types of EL light emitting layers are provided on the color filters or on the color filters and in the gaps between the color filters.
A color EL display device, characterized in that a back electrode is provided on an upper part of a dielectric layer provided in a gap between the EL light emitting layers, and the color filter and the EL light emitting layer are made to correspond to each other. 2. The color EL display device according to claim 1, wherein the color filter is a multi-layered film utilizing a light interference effect or a film utilizing a basic absorption edge of a semiconductor. 3. As red light, light emitted from a zinc sulfide phosphor layer containing divalent manganese ions as light emitting impurities, which is transmitted through a red filter formed on a translucent substrate, is used as green light. Light emitted from a zinc sulfide phosphor layer containing valent terbium ions as a luminescent impurity or a zinc sulfide phosphor layer containing trivalent terbium ions as a fluorescent impurity that has passed through a green filter is used as blue light that passes through a blue filter. 2. The color EL display device according to claim 1, wherein light emission from the strontium sulfide phosphor layer having trivalent cerium ions as a light emitting impurity is used. 4. A method for manufacturing a color EL display device according to claim 1, wherein a dielectric layer is provided.
A method for manufacturing a color EL display device, which is characterized in that it is prepared by a photolithography technique using a polyimide polymer material.