JPH01225094A - Multi-color display type electroluminescence element - Google Patents

Abstract

PURPOSE:To obtain an electroluminescence element with a two-terminal structure and allowing the primary color luminescence of each phosphor layer by laminating multiple kinds of phosphor layers with different luminous colors and intensity-voltage characteristics via insulating layers between them and between a pair of electrodes and them and providing a plane pattern-shaped light shielding thin film on adjacent phosphor layers. CONSTITUTION:If a light shielding pattern is inserted between adjacent phosphor layers, the primary color luminescence of the phosphor layer located on the display side in the display region corresponding to the light shielding pattern is obtained when both phosphor layers 4 and 6 are both illuminated, the phosphor layer with the high luminescence starting threshold value electric field Vth is located on the display side than the phosphor layer with the low Vth, thus the primary color luminescence of each phosphor layer can be attained. Multiple kinds of phosphor layers 4 and 6 with different luminous colors and intensity-voltage characteristics are laminated via insulating layers between them and between a pair of electrodes 2 and 8 which are transparent at least on the display side and them, plane pattern-shaped light shielding thin films 9 are provided between adjacent phosphor layers 4 and 6. The primary color luminescence of multiple kinds of phosphor layers can be attained with a two-terminal structure primarily.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a multi-color display type EL element (hereinafter referred to as EL), in particular, a multi-color display type EL element, in particular a plurality of types of light emitting layers between a pair of electrodes. The present invention relates to the above EL element which has a stacked two-terminal structure and is capable of emitting primary color light from each light emitting layer.

[Conventional technology]

Conventionally, as a multicolor display type EL element, a first light emitting layer is disposed between both transparent display electrodes and an intermediate electrode with an insulating layer interposed between them on both sides, and a first luminescent layer is disposed between the intermediate electrode and the back surface. A three-terminal structure is known in which a second luminescent layer having a different luminescent color from the first luminescent layer is disposed between the electrode and the first luminescent layer via an insulating layer (Japanese Unexamined Patent Application Publication No. 1986-1999). 30093, etc.).

In response, the inventors have previously developed a variable color light emitting device with a two-terminal structure that is simpler in structure and easier to manufacture than the three-terminal structure described above, and is easier to drive. There is.

In this case, multiple types of light emitting layers with different emission colors and brightness-voltage characteristics are laminated between the display electrodes and the back electrode, with an insulating layer interposed between each layer. It has the characteristic that the emitted light color can be easily changed at the same display position (IEICE+1lETD86-37
).

[Problem to be solved by the invention]

However, in the above two-terminal structure variable color light emitting EL element, when the voltage applied between both electrodes is gradually increased,
First, the light emitter layer with a lower threshold electric field (hereinafter referred to as vth) for starting light emission emits light, and by further increasing the voltage, the light emitter layer with a higher vth emits light. This results in a mixed color of the unique emitted light colors, and in principle, primary color light emission from the light emitter layer with high vth cannot be obtained.

Therefore, for example, in the case of an EL element using a red luminescent layer made of ZnS:SmFa and a green luminescent layer made of ZnS:TbF, which has a higher vth, the emitted light color may vary from red to yellow-green. Since it is not possible to obtain pure green light emission, which is the characteristic light emitting color of the latter light-emitting layer, there is a problem in that it is limited in terms of use.

This invention has been made to solve the above-mentioned difficulties, and it provides a multicolor display type ET and element that basically has a two-terminal structure and can emit primary color light from each of a plurality of types of light emitting layers. is intended to provide.

[Means to solve the problem]

As a result of extensive research in order to achieve the above object, the inventor has developed a light-shielding pattern between adjacent light-emitting layers in an EL element that includes multiple types of light-emitting layers with different emission colors and frequency-voltage characteristics. When a light-emitting layer is placed between the light-emitting layer and the light-emitting layer located on the display side, primary color light emission is obtained from the light-emitting layer located on the display side in the display area corresponding to the light-shielding pattern when both light-emitting layers are emitted. By locating the light-emitting layer on the display side than the light-emitting layer with low vth, it is possible to emit primary color light from each light-emitting layer. The present inventors have discovered that by forming such a device, a variety of light emitting displays such as each primary color emission alone, mixed color emission alone, different primary color emission combinations, and a combination of primary color emission and mixed color emission are possible, and this invention has been completed.

That is, the present invention provides a structure in which a plurality of types of light emitting layers having different emission colors and brightness-voltage characteristics are laminated between a pair of electrodes that are transparent at least on the display side with an insulating layer interposed between them and between the two electrodes. A multicolor display type E in which a light-shielding thin film in a planar pattern is provided between adjacent light emitter layers.
L relates to the element.

[Structure and operation of the invention]

FIG. 1 shows an example A of a multicolor display type EL element according to the present invention.
This shows that.

In the figure, ■ is a substrate made of a translucent material such as alkali-free glass, and on this substrate 1 is a substrate 1 made of a transparent conductive material such as indium-tin composite oxide (hereinafter referred to as ITO). Both display electrodes 2 having a thickness of about .000 to 3,000 are formed by existing thin film forming methods such as vapor deposition, sputtering, and ion blating. Then, on both display electrodes 2, a first insulating layer 3, a first light emitting layer 4, a second insulating layer 5, a second light emitting layer 6, a third insulating layer 7, A7! A back electrode 8 with a thickness of about 1,000 to 3,000 made of a film or an I'rO film is formed by the same thin film forming means as described above, and an Al film is formed inside the second insulating layer 5. A planar pattern-shaped light-shielding thin film 9 made of a non-light-transmitting material is also provided by the same thin film forming means as described above.

Here, the first light-emitting layer 4 and the second light-emitting layer 6 are formed of light-emitting materials having different emission colors and brightness-voltage characteristics, and the light-emitting material of the first light-emitting layer 4 The material has a higher vth than the same material of the second light emitting layer 6.

In such an EL element A, when an AC voltage is applied between both electrodes 2.8 and the voltage is gradually increased, v
The light-emitting layer 6 with a low th emits light, but since this light is partially blocked by the light-shielding thin film 9, it does not reach the area a on the display surface where the thin film 9 exists, but only in the area where the thin film 9 does not exist. reach. Therefore, this light emission pattern becomes a negative pattern with respect to the pattern of the light-shielding thin film 9. Then, when the applied voltage is further increased, vt
The luminescent layer 4 with a high h also starts to emit light, but since the luminescent layer 6 is blocked in the region a, the luminescent layer 4 emits the primary colors, and in the region a, the re-luminescent layers 4 and 6 emit light. Emit mixed color light. That is, in this EL element A, the light emitting layer 6
It is possible to display a display consisting of primary color emission, and a display consisting of a combination of the primary color emission of the light emitting layer 4 and the mixed color emission of both the light emitting layers 4.6, and the color tone of the mixed color emission can be changed continuously depending on the applied voltage. It can change.

FIG. 2 shows another configuration example B of the multicolor display type EL element according to the present invention.

In this EL element B, both display electrodes 2 are divided into an electrode part 2a corresponding to the area where the light-shielding thin film 9 is present and an electrode part 2b corresponding to the area where the light-shielding thin film 9 is not present. It has the same configuration as Element 8.

In such an EL element B, the training electrode portion 2 of both display electrodes 2
Since the electrodes 2a and 2b can be used selectively, a voltage that can apply an electric field equal to or higher than the Vth of the light emitting layer 4 is applied between the electrode section 2a and the back electrode 8, while the voltage between the electrode section 2b and the back electrode 8
By applying a voltage that can generate an electric field between the luminescent layer [;'s ■th] and lower than the V t ]l of the luminescent layer 4, the area a where the light-shielding thin film exists on the display surface emits light. The primary color light emission of the body layer 4 and the primary color light emission of the light body layer 6 in the non-existing area are performed, respectively, and the heat theory and the training electrode parts 2a, 2b are emitted.
It is also possible to apply a voltage to only one of the two.

Also, between the electrode part 2b and the back electrode 8, the luminescent layer 4 is
If a voltage capable of applying an electric field of h or more is applied, the regions already emit mixed color light from the re-emitter layers 4 and 6, and this mixed color light emission can be changed continuously depending on the applied voltage.

Therefore, in EL element B, the re-emitter layer 4.6
A combination of each individual primary color emission, internal color emission,
Display can be performed using a total of four light emission formats: mixed color light emission alone, and a combination of mixed color light emission and primary color light emission from the light emitter layer 4. Note that, contrary to the EL element B, the same result can be obtained even if the back electrode 8 is divided into separate electrode parts corresponding to the light-shielding thin film 9.

Furthermore, when forming one of the display electrodes 2 and the back electrode 8 into sections corresponding to the light-shielding thin film 9 as described above, it is also possible to pattern the other electrode in various ways. for example,
The light-shielding W film 9 in FIG. 2 is a striped stripe, and the corresponding training electrode portion 2a of both display electrodes 2,
In an EL element in which the back electrode 8 is patterned in a stripe shape with the back electrode 8 perpendicular to the electrode portions 2a and 2b and with twice the pitch, the light emitter layer 2b is formed in a stripe shape as shown in FIG. A light emitting display pattern is obtained in which rows of primary color light emitting regions 4a of No. 4 and rows of primary color light emitting regions 6a of light emitter layer 6 are arranged alternately.

As described above, in the EL element of the present invention, various display patterns can be created by patterning the light-shielding thin film 9 and the corresponding one electrode and the other electrode in various ways. By making the corresponding patterns of the electrodes into a fine and dense matrix shape, the E-L display has an extremely precise display pattern and can vary the emitted light color into the primary colors and mixed colors of the two light-emitting layers 4.6, either alone or in combination. can be created.

The constituent material of the first to third insulating layers 3, 5.7 is Y2
0:l,, An20. , ,SiC2,Si,N4
, Ta2os, TiO2, BaTiO3, SrTiO
3. Any of the various dielectric materials conventionally used for the insulating layer of EL devices, such as PbTiO3, can be used. Moreover, the thickness of these insulating layers is 2,000~6,
000 people is good.

The light-shielding thin film 9 may be provided in contact with one of the re-emitter layers 4 and 6, instead of being formed in the middle of the second insulating layer 5 as shown. The thickness should be sufficient to provide sufficient light-shielding properties, and will vary depending on the material used.
For example, in the case of an AI film, the number is about i,ooo~3,000 people.

As the luminescent material used for the luminescent layer 4.6, any material conventionally known for use in EL devices can be used, and is usually a matrix such as ZnS with a small amount of luminescent active agent added. , for example, ZnS:TbFz (for green emission)
and ZnS:5rnF3 (for red light emission), as well as Zn
S: Mn (for yellow-orange light emission), ZnS: TrnF3
(for blue light emission), ZnS:PrF3 (for white light emission), ZnS:DyF3 (for yellow light emission), etc. are preferably used. These luminescent materials each have different brightness-voltage characteristics and vth, but as mentioned above, the luminescent material used for the luminescent layer 4 on the display side is the same as the luminescent material used for the luminescent layer 6 on the back side. It is important to use a material with a higher vth than the material. The thickness of the light emitter layers 4 and 6 is usually 3.0
It is recommended that the number of participants be approximately 00 to 7,000.

Although the above explanation took as an example an EL element with two luminescent layers, the EL element of the present invention has three or more luminescent layers with different luminescent colors and brightness-voltage characteristics between a pair of electrodes. It may have layers. Even in such a device having three or more light emitting layers, a light-shielding thin film in a planar pattern is provided between each adjacent light emitting layer, and a light emitting layer with a high Vth is used for the display side light emitting layer. do it.

Even in this case, by separately forming one electrode for each light-shielding 1'lE tW film between each layer corresponding to the 'ljn region where the thin film exists and the region where the thin film does not exist, even more diverse luminescent displays can be achieved. Is it possible to do this?

〔Effect of the invention〕

In the EL element according to the present invention, a plurality of types of light emitting layers having different emission colors and brightness-voltage characteristics are stacked between a pair of electrodes with an insulating layer interposed between each other and between the above-mentioned two electrodes. Since the light-shielding thin film in a planar pattern is provided on the matching light-emitting layer, it basically has a two-terminal structure, and each light-emitting layer can emit primary color light. By forming the thin film separately in areas where it is present and areas where it is not present, a variety of luminescent displays can be created that can be changed to emit primary colors and mixed colors of each luminescent layer, either singly or in combination. It is possible.

〔Example〕

Hereinafter, this invention will be specifically explained based on examples.

Example 1 On one side of a substrate made of alkali-free glass with a thickness of 1.1 mm, a 2,000 mm thick TT○ was applied by sputtering.
Both display electrodes were formed in a striped pattern at regular intervals. Next, a first insulating layer of 3,000 layers of Y2O3 and a 4,000 layer of ZnS:TbF3 are sequentially deposited on the electrode side of this substrate by electron beam evaporation.
A first phosphor layer for green light emission with a high VTH of 3,000 μm thick, a second insulating layer of Y2O3 formed in two steps with a thickness of 4,000 μm of VTH A second phosphor layer for low red light emission, a third insulating layer with a thickness of 3,000 made of Y2O3, and between the formation of the first and second stages of the second insulating layer. A light-shielding thin film having a thickness of 2.000 mm and made of A7+ was formed using a resistance heating vapor deposition method in a stripe pattern corresponding to the stripe pattern of both display electrodes and having a double pitch. Finally, on the third insulating layer, a back electrode of 1,500 mm thick was formed using a resistance heating vapor deposition method, with a stripe pattern perpendicular to the stripe pattern of the light-shielding thin film and of the same pitch. A multicolor display type EL element B having the configuration shown in FIG. 2 was fabricated.

Regarding this EL element B, as shown in FIG. 3(A), a first The vth of the second light emitting layer 6 is lower than the vth of the light emitting layer 4 of
When a higher AC symmetrical pulse voltage of 200 μm was applied, only the second light emitting layer 6 emitted light, and a red light emitting display was produced in the entire area of the display surface. Also display both electrodes 2
As shown in FIG. 3(B), between the electrode part 2a and the back electrode 8 corresponding to the area where the light-shielding thin film 9 exists,
When AC asymmetrical pulse voltages of 0■ and 240■ were applied, the re-emitter layers 4 and 6 emitted light, but the light emission from the light-emitting layer 6 was blocked by the light-shielding thin film 9, resulting in a green luminescent display in area a. It has been made. By applying both mold pressures as shown in (A) and (B) above, a light-emitting display of two primary colors 'KJi', in which the light-emitting region 4a is green and the light-emitting region 6a is red, as shown in FIG. 4, was obtained.

Further, when a voltage similar to that shown in FIG. 3(B) was applied between the electrode portion 2b and the back electrode 8, a yellow-green light emission display was made in the area.

Example 2 The pattern of both display electrodes was made into a dot array that was shifted by half a pitch every other row, and the pattern of the light-shielding thin film was made into a dot array that overlapped every other row with the above dot array of both display electrodes. Except for this, an EL element was produced in the same manner as in Example 1.

Regarding this EL element, an AC sine wave voltage of 220 V was applied between the electrode part in region a of both display electrodes where the light-shielding thin film exists and the back electrode, and between the electrode part in the area where the thin film did not exist and the back electrode. When an AC sinusoidal voltage of 200 μm was simultaneously applied, a light emitting display in which green light emitting points G and red light emitting points R were arranged alternately was obtained as shown in FIG.

[Brief explanation of the drawing]

FIGS. 1 and 2 are cross-sectional views showing the structural array of a multicolor display type electroluminescent device according to the present invention, and FIGS. A waveform diagram of the AC pulse voltage used; FIG. 4 is a diagram of a light emitting display pattern obtained by the same device of Example 1 of the present invention;
FIG. 5 is a diagram of a light emitting display pattern obtained by the same device according to Example 2 of the present invention.

Claims (4)

[Claims] (1) A plurality of types of light emitter layers having different emission colors and brightness-voltage characteristics are laminated between a pair of electrodes whose display side is transparent at least, with an insulating layer interposed between them and between the two electrodes, and A multicolor display type electroluminescent device in which a light-shielding thin film in a planar pattern is provided between adjacent light-emitting layers. (2) The multicolor display type electroluminescent device according to claim 1, wherein the luminescent layer having a higher threshold electric field for starting light emission is disposed closer to the display side than the luminescent layer having a lower electric field. (3) Claim (1) wherein one electrode is formed separately corresponding to a region where the light-shielding thin film exists and a region where the light-shielding thin film does not exist.
Or the multicolor display type electroluminescent device according to (2). (4) The multicolor display type electroluminescent device according to claim (3), wherein one electrode and the light-shielding thin film are formed in a mutually corresponding matrix shape.