JPH0888088A - El element for display and its manufacture - Google Patents

Abstract

PURPOSE: To easily determine impedance to be inserted in accordance with the size of each segment and remedy uneven luminance on a display surface caused by heat generation by laying an impedance layer in the same shape as each segmant electrode has. CONSTITUTION: A light emitting layer 2 and a dielectric substance layer 3 are laminated in order over the transparent electrode 1 of a transparent conductive film and the like by means of screen printing. Resistive paste mainly composed of carbon is adhered onto a estimated laminating position for each segment electrode 4a, 4b and 4c, and formed into each resistive impedance layer 13a, 13b and 13c in an identical shape to each segment electrode. Conductive paste composed of silver, nickel, carbon and the like is adhered on the surface of each impedance layer by means of screen printing so as to be formed into each segment electrode 4a, 4b and 4c. After that, an insulating protective layer 5 made of alkyd resin and the like is formed over each segment electrode except a window hole 6, and the lead wire 7 of the conductive paste and the like is printed so as to be formed through the window hole 6.

Description

Detailed Description of the Invention

[0001]

This invention relates to an EL (Electro
-Luminescence) element, and particularly to a display EL element in which the back electrode is divided into a plurality of dot-shaped or rod-shaped segment electrodes.

[0002]

2. Description of the Related Art An EL device for display of this type is constructed so that an AC power source is appropriately switched between a transparent electrode on the front surface and a segment electrode on the rear surface to display various figures and characters on the display surface. It is used for the display of various devices.

For example, FIG. 4 shows a structural example of such a display EL element, in which a transparent electrode 1 formed of a polyester film or the like on which indium oxide, tin oxide (ITO) or the like is vapor-deposited, A phosphor layer 2 in which zinc sulfide phosphor particles activated by copper or chlorine are dispersed in an organic binder such as cyanoethyl cellulose, and a high dielectric material such as barium titanate is dispersed in an organic binder such as cyanoethyl cellulose. It has a structure in which a dielectric layer 3 and a back electrode 4 printed with a conductive paste such as silver, nickel, or carbon are sequentially laminated. The back surface electrode 4 is divided into a large number of segment electrodes 4a, 4b, 4c on the dielectric layer 3 and printed in a predetermined pattern. The upper surface side of the back surface electrode 4 is covered with an insulating protective layer 5 and each of the window holes 6 is formed. Through the lead wire 7 printed on the insulating protective layer 5,
The display EL element is constituted by these.

The EL element for display having such a structure is the transparent electrode 1
When an AC voltage is applied between the back electrode 4 and the back electrode 4, the phosphor particles of the light emitting layer 2 sandwiched between the electrodes are excited to emit light, and the divided segment electrodes 4a, 4b, 4c are appropriately applied with a voltage. By applying the voltage, a desired character or figure can be displayed.

For example, in FIG. 5A, the back surface electrode 4 is formed by dot-shaped electrodes 8 having a small diameter, and these are formed in a matrix of 7 rows and 5 columns.
FIG. 5B shows a display EL element in which the back surface electrode 4 is formed by a rod-shaped electrode 9 and is arranged in a letter-like shape. These display EL elements are composed of the transparent electrode 1 and each dot-shaped electrode 8 arranged in a pattern.
By appropriately applying a voltage to the bar electrode 9 or the bar electrode 9, various characters and figures [E in FIG. 5 (a), 2 in FIG. 5 (b)] are displayed on the display surface.

[0006]

By the way, the so-called organic EL in which the light emitting layer 2 and the dielectric layer 3 are formed by using the organic binder as described above has a life of the EL element of at most about 10,000 hours. Deterioration progresses in the frequently used segments,
Degradation is slow for the least frequently used segments. For this reason,
When these segment electrodes 4a, 4b, 4c are simultaneously driven to emit light, the electrode portions that are frequently used, for example, the shaded portions in FIGS. 5 (a) and 5 (b), become dark and display There is a problem in that there is a difference in brightness between the displayed characters and figures, resulting in reduced visibility.

As a measure for preventing the brightness difference on the display surface, for example,
As shown in FIG. 6, a method of inserting impedance elements 10a, 10b, 10c such as a resistor R and a capacitor C in the lighting circuit of each segment electrode 4a, 4b, 4c of the display EL element is adopted.

As shown in FIG. 7, this brightness difference preventing method is performed by an impedance element 1 such as a resistor R and a capacitor C.
0 is inserted in the EL element 11 in series, the voltage from the power source 12 added to the EL element 10 is divided and applied, and compensation is performed according to the characteristic deterioration of the EL element.

That is, in general, in an organic EL, as shown by a characteristic curve a in FIG. 8, the light emitting layer 2 and the dielectric layer 3 are deteriorated during lighting, the impedance thereof is increased, and the current flowing through the light emitting layer 2 is increased. Is decreased, and the emission brightness B is decreased. The decrease in the light emission brightness B is usually defined as the life when the initial light emission brightness B0 decreases by 50%.

Therefore, when the impedance element 10 for compensating for characteristic deterioration is inserted in series with the EL element 11,
When the characteristic of the element 11 deteriorates and its impedance rises as shown by the characteristic curve c, the voltage division ratio of the power source 12 applied to the EL element 11 rises accordingly, and the EL element 11 is brightly lit correspondingly, and the life characteristic is increased. Is improved as shown by the characteristic curve b. It is known that the impedance element 10 is externally attached to the lighting circuit of the EL element 11 to improve the life characteristic curve of the EL element 11 as described above, and it is also applied to the lighting circuit of the display EL element. ing.

However, in the case where the impedance elements 10a, 10b and 10c are externally attached to the lighting circuits of the respective segment electrodes 4a, 4b and 4c of the display EL element as described above, the values of the resistor R and the capacitor C to be externally attached are changed. It is necessary to set it according to the area of each segment electrode 4a, 4b, 4c, and the work is difficult.

Further, when the impedance element 10 is externally attached, for example, as shown in FIG. 9, resistance paste, capacitance paste, etc. are provided on the edge sides of the lead lines 7a, 7b, 7c of the segment electrodes 4a, 4b, 4c. By printing the impedance element 10a such as the resistor R and the capacitor C,
Although 10b and 10c are formed, the impedance element 10b may be formed on the arrangement portion of the segment electrode 4c due to a space limitation or the like. However, when the impedance element 10b is provided on the pattern of the segment electrode 4c in this manner, Joule heat is generated, and the luminance of the light emitting layer 2 in this portion is deteriorated, which may cause a luminance difference on the display surface.

Therefore, the present invention has been made in view of the problem of preventing the brightness difference on the display surface of the conventional display EL element, and is connected in series to each segment electrode,
The purpose is to make it possible to easily set the impedance of the impedance element for dividing the power supply applied to the element according to the size of each segment electrode, and to eliminate the uneven brightness of the display surface due to the heat generation of the impedance element. .

[0014]

Therefore, according to the present invention, an impedance element having the same shape as the segment electrode is laminated on the electrode surface of each segment electrode of the display EL element. The impedance element uses a carbon-based resistance paste as a material or a capacitance paste in which a high dielectric constant filler material is mixed in a resin material, and these resistance paste and capacitance paste are printed on the electrode surface of each segment to form a film. A resistance element and a capacitance element are formed. Further, in these film-shaped resistance elements and capacitance elements, a conductor layer is optionally formed on the surface of the film laminated with the dielectric layer. Further, in the display EL element, the back electrode side half body and the light emitting layer side half body are manufactured as separate bodies, and these two half bodies are integrally joined and assembled by a thermoplastic conductive resin material. The manufacturing method is adopted, and is specifically configured as follows.

That is, the display EL device of the present invention is a display EL device in which a light emitting layer, a dielectric layer and a back electrode divided into a plurality of segment electrodes are sequentially laminated on a transparent electrode.
In the element, the back surface electrode is characterized in that an impedance layer having the same shape as the electrode surface of the segment electrode is laminated on the electrode surface, and the impedance layer is laminated on the dielectric layer.

The impedance layer is made of a resistance paste mainly composed of carbon, and is printed on the electrode surface of the segment electrode to form a film-shaped resistance element.

Further, the impedance layer is made of a capacitive paste in which a paste resin material is mixed with a filler material having a high dielectric constant, and is printed on the electrode surface of the segment electrode to form a film-shaped capacitive element. It has a feature.

Further, the impedance layer is characterized in that a conductive layer having good conductivity is laminated on a surface on which the impedance layer is laminated.

In the method of manufacturing a display EL element of the present invention, the light emitting layer side half body in which the light emitting layer and the dielectric layer are sequentially laminated on the transparent electrode and the lead electrode on the back electrode substrate are provided. A plurality of segment electrodes derived and a back electrode side half body in which impedance layers are sequentially laminated are produced, and a facing surface between the dielectric layer of the light emitting layer side half body and the impedance layer of the back electrode side half body. It is characterized in that an adhesive material layer of a thermoplastic conductive paste is formed on and the two are thermally adhered via this adhesive material layer.

[0020]

[Function] Since the impedance layer is formed by printing a film on each segment electrode in the same shape as the electrode surface, the impedance of each segment electrode can be set by setting the film thickness, and the size of each electrode area can be adjusted. There is no need to calculate this accordingly. Further, although the heat generating portion is applied to the light emitting surface, it is not provided locally on the display surface and a large surface area can be taken to suppress heat generation. In addition, the deterioration due to heat generation is uniform on the display surface, and uneven brightness can be prevented. Further, since the EL element is separately manufactured into the back electrode side half body and the light emitter layer side half body, they are integrally joined and assembled, so that the manufacturing control becomes easy.

[0021]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a partial sectional view showing the structure of a display EL element according to an embodiment of the present invention.

This display EL element is also the conventional display E element.
Similar to the L element, indium oxide and tin oxide (IT.
O) or the like vapor-deposited polyester film or the like on the transparent electrode 1, zinc sulfide phosphor particles activated by copper, chlorine or the like are dispersed in an organic binder such as cyanoethyl cellulose, and a light-emitting layer 2 and titanic acid. A dielectric layer 3 in which a high dielectric substance such as barium is dispersed in an organic binder such as cyanoethyl cellulose, and a large number of segment electrodes 4a made of a conductive paste such as silver, nickel or carbon.
Each of the segment electrodes 4b and 4c has a structure in which a back electrode 4 printed in a predetermined pattern is sequentially laminated.
The a, 4b, and 4c are covered with the insulating protective layer 5, and are led out to the lead lines 7 printed on the upper surface side thereof through the window holes 6, respectively.

This EL element for display differs from the conventional EL element for display described above in that the EL element is formed on the electrode surface of each segment electrode 4a, 4b, 4c of the back electrode 4 to be laminated on the dielectric layer 3. Impedance layers 13a, 13 for dividing and applying the power supply voltage according to the deterioration of the characteristics of the
The only difference is that b and 13c are laminated, and other configurations are similar to those of the conventional display EL element. Therefore, the same components are designated by the same reference numerals as those in FIG. 4, and the description thereof will be omitted.

The impedance layers 13a, 13b, 1
3c uses a resistance paste mainly composed of carbon as a material, and adjusts it to a predetermined volume resistivity to make each segment electrode 4
Each segment electrode 4 on the electrode surface of a, 4b, 4c
a, 4b, 4c are screen-printed in the same shape, and a film-like resistance element is formed on each segment electrode 4a, 4b, 4c. d is set.

In this way, the segment electrodes 4a, 4b, 4
The display EL element in which the impedance layers 13a, 13b, and 13c are laminated on c is manufactured by using a transparent conductive film or the like as a base material and screen-printing mainly on the film as in the case of the conventional display EL element. It can be manufactured by making full use of the method and the like and sequentially laminating the film-forming layers of the respective constituent elements.

That is, the light emitting layer 2 and the dielectric layer 3 are sequentially laminated by the screen printing technique on the transparent electrode 1 made of a transparent conductive film or the like. Before stacking the segment electrodes 4 a, 4 b, 4 c on the dielectric layer 3, first, the segment electrodes 4 a, 4 on the dielectric layer 3 are stacked.
A carbon-based resistance paste, for example, a resistance paste used for the sliding surface of the volume, is screen-printed at the predetermined stacking positions of b and 4c, and the segment electrodes 4a and 4c.
b, 4c, a resistive impedance layer 13a of the same shape,
13b and 13c are formed. After that, silver, nickel, and nickel are deposited on the surfaces of the impedance layers 13a, 13b, 13c.
A conductive paste such as carbon is screen-printed to form the segment electrodes 4a, 4b, 4c. This allows
Impedance layers 13a, 13b and 13c having the same shape as the segment electrodes 4a, 4b and 4c are laminated on the dielectric layer 3 on the electrode surfaces thereof. After that, as in the conventional case, the insulating protective layer 5 such as alkyd resin is formed by leaving the window hole 6 on the upper surface side of each segment electrode 4a, 4b, 4c.
After coating, the lead wires 7 made of a conductive paste or the like may be formed by printing on the insulating protective layer 5 through the window holes 6 to lead out the segment electrodes 4a, 4b, 4c.

According to this structure, each impedance layer 13a, 13b, 13c has a segment electrode 4a.
Since they are formed by laminating in accordance with the shapes of a, 4b, and 4c, if the film thickness d of the screen printing of the impedance layers 13a, 13b, and 13c is regulated according to the volume resistivity of the resistance paste used, An impedance value can be set according to the electrode area of each segment electrode 4a, 4b, 4c. Therefore, unlike the prior art, there is no complexity of calculating impedance one by one according to the size of each segment electrode 4a, 4b, 4c, and the work is extremely simple.

Further, each of the impedance layers 13a, 1
3b and 13c are segment electrodes 4a, 4b and 4 respectively.
Since it is formed by stacking on c, it can be formed on a wider display surface than in the case where it is disposed in a very limited end area of the display surface of an EL element, which is advantageous in heat dissipation. Therefore, heat is not generated and uneven brightness is prevented. The impedance layers 13a, 13b, and 13c all have the same amount of heat generation per unit area, and even if the EL element deteriorates due to this heat generation, it uniformly deteriorates, so that the occurrence of uneven brightness is suppressed. .

Further, in this way, the segment electrodes 4a,
Resistive impedance layers 13a, 13 on 4b, 4c
In the display EL element in which b and 13c are laminated, the resistive impedance layers 13a, 13b and 13c have a circuit current limiting action, and in particular, downsizing and downsizing of an IC lighting circuit device are achieved. Suitable for

That is, each segment electrode 4a, 4b, 4c
In a device for switching the rectangular wave pulse to drive the LED for lighting, a large rush current is generated at the rising portion at the time of switching because the EL element is a capacitive load. However, the peak value of the inrush current is suppressed to an extremely small value by the impedance layer 13 laminated on each of the segment electrodes 4a, 4b, 4c, the switching circuit can be set small, and the lighting circuit can be configured at low cost.

FIG. 2 shows a display EL element according to another embodiment of the present invention. In the above embodiment, each segment electrode 4 is
Impedance layer 13 (1
3a, 13b, 13c) having a conductive layer 14 (14a, 14b, 14c) printed with a conductive paste of good conductivity such as carbon, nickel, silver or copper on the laminated surface of the dielectric layer 3 Is.

According to this structure, in forming the impedance layer 13 of the above embodiment, the segment electrodes 4a,
4b and 4c are relatively large [see, for example, FIG.
In the display EL element of (b), it is difficult to uniformly form the base electrode (not shown) provided when the dot-shaped electrode 8 and the rod-shaped electrode 9 are inverted and displayed], and its film thickness d is uniform. In this case, the brightness distribution on the display surface becomes non-uniform, but in this way,
When the low-resistance conductor layer 14 is disposed between the impedance layer 13 and the dielectric layer 3, the voltage distribution applied to the light-emitting body layer 2 below the surface on which the impedance layer 13 is formed acts so as to be uniform, Uniformity of brightness distribution can be obtained.

FIG. 3 shows each segment electrode 4a,
Impedance layers 13 (13a, 13b, 4b, 4c)
13c) is laminated to show a manufacturing method suitable for manufacturing a display EL element in which deterioration of characteristic values of the EL element is compensated, and the luminous body layer side half body 15 and the back electrode side half body 16 are shown.
A manufacturing method is adopted in which the two half bodies 15 and 16 are separately manufactured, and the two half bodies 15 and 16 are integrally joined and assembled by the thermoplastic conductive resin material 17.

That is, as shown in the drawing, the luminous body layer side half body 15 is made of polyester film or the like. T. The light emitting layer 2 and the dielectric layer 3 are sequentially laminated on the transparent electrode 1 made of a transparent conductive film on which O is formed by a screen printing method to manufacture the light emitting layer side half body 15.

On the other hand, the back electrode side half body 16 uses a PET resin film or the like as a back electrode substrate, and a plurality of segment electrodes 4a, which are led out to the lead wire 7 while keeping insulation on the back electrode substrate 18, respectively. 4b and 4c are printed and formed by a screen printing method or the like.

As shown in the figure, in order to lead the electrode to the lead wire 7, the lead wire 7 is printed on the surface of the back electrode substrate 16, and then the upper surface side is covered with an insulating protective layer 5 such as an alkyd resin. Further, segment electrodes 4a, 4b, 4c are formed by printing on the insulating protective layer 5. When printing the segment electrodes 4a, 4b, 4c, a window hole 6 is opened in the insulating protective layer 5 and connected to the lead wire 7 through the window hole 6. Alternatively, although not shown, the lead wire 7 is formed by being printed on the opposite surface (the surface on the upper surface side in the drawing) of the back surface electrode substrate 18, and the segment electrodes 4a, 4b printed on the surface of the back surface electrode substrate 16 are formed. , 4c are connected to the lead wire 7 through a window hole formed in the back surface electrode substrate 18 and led out to the outer surface side of the back surface electrode substrate 18, and various electrode lead-out structures are adopted.

Next, the rear surface electrode substrate 16 on which the segment electrodes 4a, 4b and 4c are printed is divided into segment electrodes 4a,
Impedance layers 13a, 13b, 13 on 4b, 4c
c, thermoplastic conductive adhesive layer 17 (17a, 17b, 1
7c) is sequentially laminated in the same shape as the segment electrodes 4a, 4b, 4c by a screen printing method, and the back electrode side half body 1
Produce 6.

Then, the light emitting layer side half body 15 and the back surface electrode side half body 16 thus manufactured are integrally joined by a hot pressing device with their joining surfaces facing each other as shown in the figure.

According to such a manufacturing method, the back electrode side half body 16 can firmly bond the thermoplastic conductive adhesive layer 17 and the dielectric layer 3, and at the same time, the thermoplastic conductive adhesive layer can be obtained. 17 covers the non-uniformity of the impedance layer 13, for example, the non-uniformity due to the porous property of the impedance layer 13 itself or the changeability due to the solvent, or the non-uniformity due to the variation in the thickness of the impedance 13 layer. It

Further, the back electrode side half body 16 is usually provided for each segment electrode 4 for each design of the display EL device to be manufactured.
Although the patterns a, 4b, 4c and the lead-out patterns of the lead lines 7 are different, the light emitter layer side half body 15 is common, and a desired display EL device can be appropriately manufactured by combining these. Production management becomes easy.

In each of the above embodiments of the present invention, the impedance layer 13 is formed of a carbon-based resistance paste to form a resistive impedance element. The resin material for the paste is used as a filler having a high dielectric constant. Even if a capacitive impedance element is formed by using a capacitive paste mixed with a material, the characteristic deterioration of the EL element can be similarly compensated.

[0043]

As described above, according to the present invention, the impedance element having the same shape is laminated on each segment electrode of the display EL element, so that the segment electrode is inserted depending on the size of the segment electrode. The impedance of the lighting circuit can be easily set. Further, heat generation on the element surface due to mounting the impedance element can be reduced, and unevenness in display brightness can be improved.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view showing a configuration of a display EL element according to an embodiment of the present invention.

FIG. 2 is a partial cross-sectional view showing the structure of a display EL element according to another embodiment of the present invention.

FIG. 3 is a partial cross-sectional view showing the manufacturing process of the display EL element of the present invention.

FIG. 4 is a partial cross-sectional view showing a configuration of a conventional display EL element.

5A and 5B are pattern diagrams of a back surface electrode of a display EL element, FIG. 5A is a pattern diagram of a dot electrode, and FIG. 5B is a pattern diagram of a rod electrode.

FIG. 6 is an explanatory diagram of a measure for preventing uneven brightness on the display surface of a conventional display EL element.

FIG. 7: Lighting circuit diagram of EL element

FIG. 8 is a characteristic curve diagram of an EL element over time.

FIG. 9 is an explanatory diagram of luminance unevenness on a display surface of a conventional display EL element.

[Explanation of symbols]

 1 Transparent electrode 2 Light emitter layer 3 Dielectric layer 4 Back electrode 4a to 4c Segment electrode 13a to 13c Impedance layer 14a to 14c Conductor layer 15 Light emitter layer side half body 16 Back electrode side half body 17a to 17c Thermoplastic conductivity Resin material (adhesive layer) 18 Backside electrode substrate

Claims (5)

[Claims] 1. A display EL device comprising a transparent electrode, a light emitting layer, a dielectric layer, and a back electrode divided into a plurality of segment electrodes, which are sequentially laminated, wherein the back electrode is on the electrode surface of the segment electrode. An EL element for display, wherein an impedance layer having the same shape as the electrode surface is laminated and laminated on the dielectric layer. 2. The display EL element according to claim 1, wherein the impedance layer is made of a carbon-based resistance paste and is printed on the electrode surface of the segment electrode to form a film-shaped resistance element. 3. The impedance layer is made of a capacitive paste obtained by mixing a paste resin material with a filler material having a high dielectric constant, and is printed on the electrode surface of the segment electrode to form a film-shaped capacitive element. The display EL device according to claim 1, which is characterized in that. 4. The EL device for display according to claim 2, wherein the impedance layer is formed by laminating a conductive layer having good conductivity on a laminating surface on which a dielectric layer is laminated. 5. A luminous body layer side half body in which a luminous body layer and a dielectric layer are sequentially laminated on a transparent electrode, and a plurality of segment electrodes led out to a lead wire on a back electrode substrate, respectively.
A back electrode side half body in which impedance layers are sequentially laminated is produced, and a thermoplastic conductive paste adhesive layer is provided on a surface facing the dielectric layer of the light emitter layer side half body and the impedance layer of the back electrode side half body. And a heat-bonding the both through the adhesive layer.