JPH08171988A - Electroluminescence element - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide an electroluminescent element having both sufficient water resistance and weather resistance and being easy to manufacture. [Structure] On a glass substrate 2, a transparent electrode layer 3, a light emitting layer 4,
The insulating reflection layer 5 and the back electrode layer 6 are laminated, and the back protective film 8 is adhered to the laminate and the glass substrate 1 via the hot melt adhesive layer 7 so as to cover these laminates. ing. That is, by the hot melt adhesive layer 7 and the back protective film 8,
A laminated body from the transparent electrode layer 3 to the back electrode layer 6 is laminated on the glass substrate 2. In that case, the hot melt adhesive layer 7 is made of SEPS-based synthetic rubber or SEBS.
It is composed of a hot-melt adhesive whose main material is a system synthetic rubber. The SEPS-based synthetic rubber or the SEBS-based synthetic rubber makes the EL element 1 excellent in water resistance and weather resistance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to electroluminescence (hereinafter,
(Also referred to as EL) element.

[0002]

2. Description of the Related Art Generally, an EL element includes a transparent electrode on the front surface from which light is emitted, a back electrode facing the transparent electrode, a light emitting layer and an insulating reflection layer disposed between these two electrodes. Is formed as a surface light emitter. Then, in the EL element, the light emitting layer emits light when an alternating electric field is applied between the electrodes, and the light is directly reflected by the insulating reflection layer and radiated to the outside through the transparent electrode. Current,
Such EL elements are variously used in, for example, backlights of liquid crystal display devices, illumination, display elements using light, and guide display boards using indoor and outdoor light.

As an example of such an EL element, there is an EL element disclosed in JP-A-62-188197. As disclosed in this publication, the EL element is mainly a glass substrate type and a film substrate. There is a type. Figure 2
FIG. 3 is a sectional view showing a glass substrate type EL element of this publication, and FIG. 3 is a film substrate type E element of this publication.
It is sectional drawing which shows an L element.

As shown in FIG. 2, a glass substrate type E
The L element 21 includes a transparent electrode film 23, a light emitting element 24, an insulating film 2 on a tempered plate glass 22 which is a glass substrate.
5, the aluminum electrode 26, and the protective film 27 on the back surface are stacked, and these are laminated by the intermediate film 28.

Further, as shown in FIG. 3, a film substrate type EL element 29 is formed by using a film substrate 30 in place of the tempered glass plate 22 in the glass substrate type EL element 21 described above. It is almost the same as the glass substrate type EL element 21 described above. The film substrate 30 is made of clear PVF (polyvinyl fluoride film), which makes the EL element 29 flexible.

In each of the EL elements 21 and 29 shown in FIGS. 2 and 3, ethylene vinyl acetate (hereinafter also referred to as EVA) is used as a laminating agent forming the intermediate layer 28. The EVA prevents the light emitting element 3 from absorbing moisture and blocks ultraviolet rays.

In addition to EVA, polyamide, acrylic, urethane, epoxy, nylon, olefin adhesives, etc., and synthetic rubber polymer materials such as nitrile rubber and chloroprene rubber are also used as laminating agents. Is used.

[0008]

By the way, the EL element is often used outdoors depending on its application. When EL elements are used outdoors, they are frequently exposed to the UV rays of rain and sunlight, and as a result, deterioration is less likely to occur without being affected by these rain and UV rays. You are forced to the strict condition that you must

Therefore, it is necessary to protect the light emitting element of the EL element from such rain and ultraviolet rays, but for that purpose, the EL element must have both water resistance and weather (light) resistance.

However, although the EVA-based adhesive has a certain degree of water resistance as described above, as expected from the fact that it has a hydrophilic group such as a carboxyl group in the molecule, the EL element is under severe conditions. When it is used outdoors, the water resistance is not sufficient, and there is a problem that the light emitting element of the EL element used outdoors cannot be sufficiently protected against water. Further, polyamide-based, acrylic-based, urethane-based, epoxy-based, nylon-based, olefin-based, etc. adhesives are also not sufficient for the moisture absorption inhibiting performance required when the EL element is used outdoors in the same manner. .

Further, since the EVA type adhesive is slippery, it is difficult to align the tempered plate glass 22 and the protective film 27 with the transparent electrode film 23, the light emitting element 24, the insulating film 25 and the aluminum electrode 26, and the manufacturing work is difficult. Is relatively difficult.

On the other hand, the above-mentioned synthetic rubber type polymeric substance is
Although it has a relatively good water resistance and can reliably protect against water when the EL element is used outdoors, it does not have sufficient weather resistance and is used outdoors.
There is a problem that the light emitting element of the L element cannot be sufficiently protected against ultraviolet rays. In this way, conventional EL
Since the element does not have both water resistance and weather resistance, it is difficult to use it outdoors.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an electroluminescent element having both sufficient water resistance and weather resistance and being easy to manufacture. is there.

[0014]

In order to solve the above-mentioned problems, the invention of claim 1 provides a transparent electrode layer laminated on a transparent substrate, and a light-emitting body laminated on this transparent electrode layer. Layer, an insulating reflection layer laminated on the light emitting layer, and a back electrode layer laminated on the insulating reflection layer so as to cover the back electrode side of the SEPS (styrene-ethylene -Propylene / styrene block copolymer-based synthetic rubber or SEBS (styrene-ethylene-butylene-styrene block copolymer) -based synthetic rubber as the main material It is characterized by laminating a protective film.

The invention of claim 2 is characterized in that the substrate is a glass substrate. Furthermore, the invention of claim 3 is characterized in that the substrate is a film substrate.

[0016]

In the electroluminescent device of the present invention having such a structure, the light emitting layer of the electroluminescent device is a synthetic rubber of SEPS type or SEBS.
It will be laminated with an adhesive layer composed mainly of a synthetic rubber of the type. These SEPS-based synthetic rubbers or SEBS-based synthetic rubbers also have hydrophilic groups such as carboxyl groups present in conventionally used EVA and the like,
It does not have a double bond in the molecule like synthetic rubber.
Therefore, the adhesive layer containing SEPS-based synthetic rubber or SEBS-based synthetic rubber as a main material is
It has excellent water resistance and weather resistance.
As a result, the EL device of the present invention can surely protect the light emitting layer from rain and ultraviolet rays even when it is used outdoors under severe conditions.

Further, SEPS synthetic rubber or SEB
The S-based synthetic rubber is relatively non-slip, and therefore the alignment between the layers becomes easy, and the EL element can be manufactured more easily.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing an embodiment of a glass substrate type of an electroluminescence device according to the present invention.

As shown in FIG. 1, in the glass substrate type EL element 1 of this embodiment, a transparent electrode made of a transparent conductive film of tin oxide SnO ₂ or indium tin oxide ITO is formed on one surface of the glass substrate 2. The layer 3 is formed, and the light emitting layer 4 is formed on the upper surface of the transparent electrode layer 3. The light-emitting layer 4 is formed by dissolving a high dielectric constant polymer substance in a solvent such as dimethyl formamide, methylpyrrolidone or prolylen carbonate, and dispersing a zinc sulfide-based phosphor in this solution. It is formed by forming an ink, printing and coating the ink on the upper surface of the transparent electrode layer 3, and then sufficiently drying.

An insulating reflective layer 5 is formed on the upper surface of the light emitting layer 4. The insulating reflective layer 5 has a high dielectric constant such as barium titanate or titanium oxide in a high dielectric constant polymer solution and has a hiding power. The white powder is dispersed to form an ink, the ink is printed and applied on the upper surface of the light-emitting body 4, and then dried sufficiently. Further, a back electrode layer 6 is formed on the upper surface of the insulating reflection layer 5. Then, the hot-melt adhesive layer 7 covers the laminated body from the transparent electrode layer 3 to the back electrode layer 6 formed on the glass substrate 2 in this way, and the back protective film 8 forms the laminated body and the glass. It is bonded to the substrate 1. The hot melt adhesive layer 7 and the back protective film 8 are made of SEPS (styrene / ethylene / propylene / styrene block copolymer) synthetic rubber or SEBS (styrene / ethylene / butylene / styrene block copolymer). It is provided by hot-pressing a composite film coated with a hot-melt adhesive containing a synthetic rubber as a main material, for example, an aluminum foil, so as to cover the above-mentioned laminate. There is. In the figure, 9 and 10 are the transparent electrode layer 3 and the back electrode layer 6, respectively.
Is a lead wire for applying an alternating electric field to the outside.

In this way, the hot melt adhesive layer 7
Further, the back surface protective film 8 constitutes the glass substrate type EL element 1 in which the laminated body from the transparent electrode layer 3 to the back electrode layer 6 is laminated on the glass substrate 2.

The EL element 1 thus constructed has the transparent electrode layer 3 and the back electrode layer 6 via the lead wires 9 and 10.
By applying an alternating electric field between them, the light emitting layer 4 emits light, and this light is emitted to the outside through the transparent electrode layer 3 and the glass substrate 1.

By the way, in the SEPS synthetic rubber or SEBS synthetic rubber used for the hot melt adhesive layer 7, hydrophilic groups such as a carboxyl group present in EVA are also contained in the above rubber type. So there is no double bond in the molecule. Therefore, SEPS synthetic rubber or S
The hot melt adhesive layer 7, which is mainly made of EBS-based synthetic rubber, has very excellent water resistance and weather resistance as compared with the conventional one. As a result, the EL of this embodiment is
Even when the element 1 is used outdoors under the severe conditions described above, the light emitting layer 4 is surely protected from rain and ultraviolet rays.

Actually, an EL element using the SEBS type synthetic rubber of this embodiment, an EL element using the conventional EVA type resin
An outdoor exposure test was conducted using the element, an EL element using a conventional nitrile rubber-based synthetic rubber, and the results are shown in Table 1.

The test piece of the EL element used for the test had the same laminated structure as that shown in FIG. 1 and was manufactured as follows. First, a 140 mm × 20 mm × 2 mm glass substrate on which a transparent electrode film of SnO ₂ was formed and an ink in which a ZnS light-emitting material was dispersed in a resin solution prepared by dissolving cyanoethyl pullulan, which is a resin with a high dielectric constant, in propylene carbonate was used. A light emitting layer was formed by preparing and printing this ink on a transparent electrode film of a glass substrate and drying it. Next, an ink in which barium titanate or titanium oxide was dispersed in the same resin solution as described above was prepared, and this ink was applied by printing onto the light emitting layer and dried to form an insulating reflective layer. Then, a conductive ink was applied by printing onto the insulating reflective layer and dried and cured to form a back electrode layer. Next, prepare a hot melt adhesive mainly composed of SEBS synthetic rubber in the PET / AL foil / PET composite film, apply this hot melt adhesive to a thickness of about 50 μm, and attach the back protective film with the adhesive. Formed. Next, this back protective film with an adhesive was applied to the back electrode layer side of the glass substrate, and heated and pressure bonded with a vacuum laminator. Finally, a lead wire was connected to each of the electrode layers of the finished product, and the connection portion was waterproofed with a UV curable resin to prepare a test piece of an EL device using the SEBS of the present invention.

Further, in order to compare the effect of the SEBS adhesive of this test piece, an EL element test piece using a conventional EVA adhesive and nitrile rubber adhesive was prepared. In that case, instead of SEBS of the above-mentioned hot melt adhesive, an EVA-based adhesive and a nitrile rubber-based adhesive were formed on the same composite film to prepare an adhesive-backed protective film. In addition, these conventional E
EL using VA adhesive and nitrile rubber adhesive
The other structure of the device test piece is the same as that of the EL device test piece using the SEBS of the present invention.

As the test method, the test piece was set on a cradle installed at an outdoor exposure test location, tilted at about 45 degrees so that it was exposed to sunlight. A test was conducted by exposing the EL element in a lighting state in which deterioration progressed quickly.

Further, the following three methods were used as the method for judging the test result, and the test result was judged by the comprehensive judgment thereof. That is, (1) Judgment of deterioration state due to change in appearance, (2) Judgment of deterioration state due to change due to moisture ... When water enters from the periphery of the EL element and reaches the light emitting surface, blackening or Since black browning begins, comparison was made at the start of this discoloration (until moisture reaches the light emitting surface,
(It is almost impossible to judge the moisture penetration from the appearance), (3) Judgment of deterioration state based on changes due to ultraviolet rays ... It is considered that ultraviolet rays deteriorate due to the synergistic action with water and / or oxygen. In the cross-section where the adhesive part on the outer periphery is exposed (contact part with air), for example, in the case of a nitrile rubber adhesive, the color changes to brown, and this gradually progresses, and the light emitting surface begins to change color. Compared with.

[0029]

[Table 1]

As is clear from Table 1, the EL element using the conventional EVA resin starts to deteriorate due to moisture around the element as a result of exposure for 30 days, and the conventional nitrile rubber synthetic rubber is used. It can be seen that, as a result of the exposure for 90 days, the EL device thus formed begins to deteriorate from the periphery of the device, which is considered to be caused by ultraviolet rays and oxygen. On the other hand, the EL device using the SEBS synthetic rubber of this embodiment is
As a result of exposure for 210 days, no abnormality was observed.

As described above, the glass substrate type EL element 1 of the present embodiment has far superior water resistance and weather resistance as compared with the conventional ones, is not easily deteriorated even when used outdoors, and is suitable for outdoor use. It turns out that it can be sufficiently dealt with.

In the above-mentioned embodiment, the case where the present invention is applied to the glass substrate type EL element 1 has been described. However, the present invention uses a transparent film substrate such as polyester instead of the glass substrate. Needless to say, it can be applied to the film substrate type EL element used, but in this case, in order to prevent moisture absorption from the film substrate such as polyester film, a fluororesin film (PCTFE) with a low hygroscopicity is laminated on this film substrate. Will be required. This film substrate type EL element also has the same effect as the glass substrate type EL element described above.

[0033]

As is apparent from the above description, according to the electroluminescence element of the present invention, the light emitting layer of the electroluminescence element is bonded by using SEPS synthetic rubber or SEBS synthetic rubber as a main material. Since the EL element is laminated with the agent layer, the EL element is very excellent in water resistance and weather resistance. As a result, the E
Even if the L element is used outdoors under severe conditions,
The light emitting layer can be reliably protected from rain and ultraviolet rays.

Further, SEPS synthetic rubber or SEB
By using the S-based synthetic rubber, the alignment between the layers is facilitated, so that the EL element is further easily manufactured.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of a glass substrate type of an electroluminescence element according to the present invention.

FIG. 2 is a sectional view showing an example of a conventional glass substrate type electroluminescence element.

FIG. 3 is a sectional view showing an example of a conventional film substrate type electroluminescence element.

[Explanation of symbols]

1 ... Glass substrate type EL element, 2 ... Glass substrate, 3
... transparent electrode layer, 4 ... luminescent layer, 5 ... insulating reflection layer, 6 ... back electrode layer, 7 ... hot melt adhesive layer mainly made of SEPS or SEBS synthetic rubber, 8 ... back protective film,
9, 10 ... Lead wire, 21, 29 ... EL element, 22 ... Reinforced plate glass, 23 ... Transparent electrode film, 24 ... Light emitting element,
25 ... Insulating film, 26 ... Aluminum electrode, 27 ... Protective film, 28 ... Intermediate film, 30 ... Film substrate

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Junichi Murakami 1105 Nikko, Kunomoto, Tendo City, Yamagata Prefecture Tohoku Pioneer Corporation

Claims (3)

[Claims] 1. A transparent electrode layer laminated on a transparent substrate, a light emitting layer laminated on the transparent electrode layer, an insulating reflection layer laminated on the light emitting layer, and an insulating layer. The SEPS (styrene / ethylene / styrene / ethylene / ethylene /
Propylene / styrene block copolymer-based synthetic rubber or SEBS (styrene / ethylene / butylene / styrene block copolymer) -based synthetic rubber is used as the main material, and an impermeable back surface is protected through an adhesive layer. An electroluminescence device characterized by laminating a film. 2. The electroluminescent element according to claim 1, wherein the substrate is a glass substrate. 3. The electroluminescent element according to claim 1, wherein the substrate is a film substrate.