JPH04138688A - Method of sealing electroluminescent element - Google Patents

Abstract

PURPOSE:To obtain a long-life electroluminescent element by using multilayer films for sealing, and sandwiching an electroluminescent element between the films, and then carrying out evacuation so as to deform the films, and sticking sealant layers together. CONSTITUTION:A multilayer film A having a transparent thin film 2 of silicon oxide on one side of a polyvinyl alcohol film of the degree of saponification more than 99mol% and a multilayer film B having the same thin film 4 are laid one on the other and laminated and transparent sealant layers C which can be sealed together by heat are formed on the film surface side of the multilayer film A. An electroluminescent element 21 is sandwiched between the sealant layers located between such films 22, 23 and is placed between a flexible film and a base which can be heated and applying evacuation to deform the films and the sealant layers are stuck together and sealed together by heat so as to prevent destruction of a metal oxide thin plate during sealing. A long-life electroluminscent element whose luminance scarcely deteriorates with time can thus be obtained.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for encapsulating an EL (electroluminescence) device, and more specifically, a method for sealing an EL (electroluminescence) device, which has excellent transparency and moisture resistance, and whose brightness changes over time. The present invention relates to a sealing method for an organic dispersion type packaged EL element that has a long life and has a small degree of decrease in .

[Conventional technology]

Liquid crystal display elements have become established as display elements for digital watches and electronic desk calculators, taking advantage of their greatest feature of being able to drive with low power consumption. Demand for them has expanded explosively with the advent of liquid crystal games. after that,
Applications are becoming more diverse, including automotive use, musical instruments, OA use, and FA use.

On the other hand, organic dispersion film type EL devices have phosphor for EL dispersed in a polymeric dielectric layer, and take advantage of their thinness and light weight to be used as inexpensive flat-emitting backlights for liquid crystal display devices ( Its use as an auxiliary light source is becoming increasingly widespread.

By the way, in an organic dispersion film type EL element, Z
Since the luminance of phosphors such as nS:Mn and ZnS:Cu is significantly impaired by moisture absorption, they are sealed with a film with excellent moisture-proofing performance and transparency and used as a packaged EL device.

FIG. 7 is an explanatory diagram of a conventionally generally employed sealing method for an EL element.

The conventional sealing method uses two sealing films (22), (2
3), and the organic dispersion film type EL element (21) sandwiched between the sealant layers of these two sealing films is placed in an appropriate nip between the upper and lower heating rolls (24) and (25). This method heat-seals the sealant layer around the entire EL element by passing it under pressure.

Conventionally, fluorinated resin films, particularly polychlorinated trifluoroethylene (PCTF), have been used as sealing films.
Laminated films based on E) are recommended because they have excellent moisture-proofing performance and transparency.

[Problem to be solved by the invention]

However, since the laminated film mainly made of PCTFE is extremely expensive, there is a problem in that the manufacturing cost of the backlight increases. In addition, the moisture-proof performance of this laminated film deteriorates considerably when the ambient temperature exceeds 50° C., so there is a problem that the life of the EL element becomes extremely short at high temperatures.

Recently, transparent laminated plastic films, in which a transparent thin film of a metal oxide, particularly silicon or aluminum, is provided on the surface of a transparent plastic film, have been commercialized as packaging materials with gas barrier properties.

The above-mentioned transparent laminated plastic film is cheaper than a laminated film mainly made of PCTFE, and can also be used as a sealing film because it can exhibit reasonable moisture-proofing performance even at relatively high temperatures. However, in the conventional sealing method, the metal oxide thin film is destroyed when passing through the heating roll, and moisture-proof performance cannot be maintained.

The present invention has been made in view of the above-mentioned circumstances, and its purpose is to provide an organic dispersion type packaged EL device that has excellent transparency and moisture resistance, has a long lifespan, and has very little reduction in brightness over time. An object of the present invention is to provide a sealing method for an element.

[Means to solve the problem]

As a result of intensive studies to solve the above-mentioned problems, the present inventors found that the above-mentioned transparent laminated plastic film can be used as a sealing film if a specific sealing method is adopted. As a result, the present invention was completed.

That is, the gist of the present invention is to provide a sealing material comprising one or more transparent laminated films having a transparent thin film of metal oxide on at least one side of a transparent plastic film, and one side of which is a heat-sealable transparent sealant layer. After sandwiching an organic dispersion film type EL element between the sealant layers of these two sealing laminated films, this is placed between a flexible film and a heatable substrate. The flexible film is placed in place and a vacuum is drawn between the flexible film and the heatable substrate to deform the flexible film, and the deformation of the flexible film brings the sealant layers of the sealing laminated film into close contact with each other. E characterized by heat sealing
The present invention relates to an L element sealing method.

The present invention will be explained in detail below.

First, the sealing film used in the present invention will be explained.

In the present invention, the sealing film includes one or more transparent laminated films having a transparent thin film of metal oxide on at least one side of a transparent plastic film, and one side of which is made of a heat-sealable transparent sealant layer. A laminated film for sealing is used.

Examples of transparent plastic films include stretched or unstretched films such as polyvinyl alcohol, polyester, polyolefin, and polyamide, and examples of metal oxide thin films include AI, Si, Zn, Zr,
Mention may be made of thin films of oxides of Sn, In, Ti and mixtures thereof.

The transparent laminated film is constructed by forming a transparent thin film of the metal oxide on at least one side of the transparent plastic film, and the metal oxide thin film is formed by a method such as vacuum evaporation or sputtering. . The metal oxide thin film is usually formed on only one side of the transparent plastic film.

The thickness of the above transparent plastic film is usually 5~
400μ, preferably in the range of 10 to 200μ, and the thickness of the metal oxide thin film is usually in the range of 100 to 5000μ.

In the present invention, the transparent plastic film suitably used is a polyvinyl alcohol film having a degree of saponification of 99 mol% or more, and the metal oxide thin film suitably used is a silicon (Si) oxide thin film. Generally, a transparent laminated film having a silicon oxide thin film on the surface of a polyvinyl alcohol film having a degree of saponification of 99 mol % or more is mainly used. The polyvinyl alcohol film may be stretched or unstretched, but
A biaxially stretched film stretched to about 3×3 times is preferred.

The sealing film used in the present invention includes one or more of the above-mentioned transparent laminated films, but specifically, one or more transparent laminated films are used, or a transparent laminated film and a transparent plastic film are used. Use in combination. In either case, it is preferable to have a layer structure in which the metal oxide thin film is not located on the outer surface. For example, two transparent laminated films in which a metal oxide thin film is formed on only one side of a transparent plastic film are used. In such cases, it is preferable to use metal oxide thin films in a stacked manner.

The sealing film used in the present invention must have a heat-sealable transparent sealant layer laminated on one side thereof.

As the heat-sealable transparent sealant layer, transparent sealant films such as ethylene-vinyl acetate copolymer (EVA) and unstretched polypropylene film (CPP) can also be used; From the viewpoint of adhesiveness of the metal terminals of the element, a sealant layer using ethylene-ethyl acrylate-h (EEA) or ethylene-acrylic acid copolymer (EAA) is suitable.

The thickness of the above-mentioned sealant layer is usually in the range of 20 to 100 microns.

Further, although the above-mentioned transparent laminated films and sealant layers can be laminated by any appropriate method, it is convenient to use a transparent adhesive such as urethane-based, acrylic-based, or polyester-based adhesive.

FIG. 1 is an explanatory diagram showing an example of a sealing film used in the present invention.

In the figure, (A) is a transparent laminated film with a transparent thin film (2) of silicon oxide formed on one side of a polyvinyl alcohol film (1) with a degree of saponification of 99 mol% or more, and (B) is a polyester film (3). A transparent laminated film with a transparent thin film (4) of silicon oxide formed on one side of the film, (C) is EE
This is a heat-sealable transparent sealant layer made of A film (6). Then, the transparent laminated films (A) and (B) are laminated by overlapping silicon oxide thin films,
The sealant layer (C) is laminated on the polyvinyl alcohol film side of the transparent laminated film (A).

Note that (5) and (7) are transparent adhesive layers used for lamination.

Next, the EL element sealing method of the present invention will be explained.

The sealing method of the present invention uses two of the above-described laminated sealing films, sandwiching the EL element between the sealant layers of these two laminated sealing films, and then heating the EL element with a flexible film. A vacuum is drawn between the flexible film and the heatable substrate to deform the flexible film, and the deformation of the flexible film causes the sealing laminated film to It consists of a method of heat sealing by bringing sealant layers into close contact with each other.

FIG. 2 is a side view conceptually showing an example of a vacuum sealing machine suitably used in the sealing method of the present invention, FIG. 3 is a plan view thereof, and FIG. 4 is an explanatory diagram of a heat-sealed state. .

The vacuum sealing machine described above is composed of an insertion stage (8) and a heating stage (9).

The insertion stage (8) consists of an upper surface (10), a lower surface (11) and a fulcrum (12). As shown in FIG. 4, the upper surface (10) consists of a frame-shaped clamp (13) and a heat-resistant flexible film (14), and the lower surface (10)
1) consists of a heatable substrate (16) made of stainless steel or the like around which a frame-shaped clamp (15) is arranged.

The flexible film (14) is usually made of polyester, Teflon, nitrile rubber, silicone rubber, etc., and is actually supported by being sandwiched between the clamp (13) and the clamp (15). There is.

In addition, in this specification, the above-mentioned word "film" means
The concept is used to include sheets as long as they have flexibility that can be deformed at atmospheric pressure by the decompression action described later.

As shown in Fig. 2, the upper surface (10) can be opened and closed with respect to the lower surface (11) with the fulcrum (12) as the central axis, and each of the above-mentioned clamps is formed into a frame of the same size. ing.

Vacuum holes (17) are provided on the left and right sides of the substrate (16) constituting the lower surface (11).

The heating stage (9) consists of a heating furnace, and inside the heating furnace there is a rod-shaped heater (19) equipped with a reflector (18).
are arranged, and furthermore, an insertion stage (8
A rail (20) is provided which extends up to ).

First, as shown in FIG.
23) and inserted between the flexible film (14) and the substrate (16).

Next, the vacuum holes (17) provided in the substrate (16), (
17) Perform vacuuming.

As a result of the above evacuation, the flexible film (14) is deformed by the action of atmospheric pressure, as shown in FIG. 4, and comes into close contact with the laminated film (22), deforming it. As a result, as shown in FIG. 4 (or FIG. 6), the sealant layers of the sealing laminated films (22) and (23) are in close contact with each other.

Next, as shown in FIG. 4, in the above state, the upper surface (1
0) and the lower surface (11) are moved into the heating stage (9) along the rail (20) and heat sealed.

FIG. 6 is an explanatory diagram of the packaged EL device thus obtained.

By being configured as described above, the sealing method of the present invention prevents the metal oxide thin film of the sealing laminated film from being destroyed during sealing.

Therefore, the packaged EL device obtained by the present invention has significantly improved luminance deterioration over time.

〔Example〕

Hereinafter, the present invention will be described in detail based on Examples and in contrast with Comparative Examples, but the present invention is not limited to the following Examples unless it exceeds the gist thereof.

In the following examples, the moisture permeability of the sealing laminated film and the change in luminance over time of the packaged 1"EL element were measured by the following method.

(1) Moisture permeability (gr/bo 24H) Measured using a water vapor permeation tester manufactured by Modern Control under conditions of a temperature of 40° C. and a relative humidity of 90%.

(2) Change in brightness (%) A packaged EL element with a light emitting surface size of 20 x 50 mm was left for 240 hours under high temperature and high humidity conditions of 60°C x 90% RH, and one was not left under high temperature and high humidity conditions. Prepare two things, turn on electricity and emit light for each, 1
After a period of time, packaged E left under high temperature and high humidity conditions
The area where the luminance of the L element was reduced was measured, and the area ratio of the luminance reduced portion to the entire light emitting surface of the EL element was determined.

Note that the packaged EL element that was not left under high temperature and high humidity conditions was used to confirm that there was no decrease in brightness over the entire light emitting surface of the EL element.

Example 1 Creation of a laminated film for soil use> A polyvinyl alcohol film with a degree of saponification of 99.9 mol% (stretching ratio 3 x 3 times, biaxial stretching, thickness 25 μm) was coated with 5 x 10-” Torr on the surface. Silicon monoxide (Sin) with a purity of 99.9% is heated and evaporated using an electron beam heating method under a vacuum of A transparent laminated plastic film was obtained (A
film).

In addition, a transparent thin film of 1000 silicon oxides was formed on the surface of a polyethylene terephthalate (PET) film (stretching ratio 3x3, biaxial stretching, thickness 50 μm) using the same thin film forming method as above. A transparent laminated plastic film was obtained (B film).

Film A and Film B are laminated using a urethane-based adhesive, with thin silicon oxide films stacked on top of each other, and an ethylene ethyl acrylate film (
EEA (thickness: 50 μm, non-stretched) was similarly laminated using a urethane adhesive to obtain a sealing laminated film as shown in FIG.

<Sealing of EL element> Two pieces of 25 x 65 mm are cut out from the above-mentioned sealing laminated film, and a 20 x 50 mm organic dispersion film type EL element is sandwiched between them, and the insertion stage explained in Figs. 2 to 4 above is performed. (8) was placed on the substrate (16) constituting the lower surface (11).

Next, the upper surface (10) is lowered, the lower surface (11) is covered with a flexible film (14), and vacuum is drawn through the vacuum holes (17), (17) provided in the substrate (16) for sealing. The sealant layers of the laminated film are brought into close contact with each other, and the rails (2
0), the furnace was transferred to the heating stage (9) where the temperature inside the furnace was set at 120°C, heated for 20 seconds, and then transferred to the insertion stage (8) again, where the flexible film (14
) and the substrate (16) to the atmosphere.
A shielded EL element as shown in the figure was obtained.

Table 1 shows the measurement results of the moisture permeability of the sealing laminated film and the change in luminance over time of the packaged EL element.

Example 2 In Example 1, a polypropylene film without a silicon oxide thin film (stretching ratio 3 x 3 times, biaxial stretching, thickness 50μ) was used instead of the 50μ PET film having a silicon oxide thin film. Otherwise, the sealing laminated film was prepared and the EL element was sealed in the same manner as on the same side.

Table 1 shows the measurement results of the moisture permeability of the sealing laminated film and the change in luminance over time of the packaged EL element.

Comparative Example 1 In Example 1, a 25μ PVA film without a silicon oxide thin film was used in place of the 25μ PVA film with a silicon oxide thin film, but the same procedure as on the same side was used for sealing. A laminated film was created and an EL element was sealed.

Table 1 shows the measurement results of the moisture permeability of the sealing laminated film and the change in luminance of the packaged EL element over time.

Comparative Example 2 The same laminated film for sealing as in Example 1 was used, the heating roll method shown in Figure 7 was adopted, and the humidity of the heating roll was reduced to 1.
20℃, nip pressure between two rolls l Okg/cr
! The EL element was sealed under the following conditions.

Table 1 shows the measurement results of the moisture permeability of the sealing laminated film and the change in luminance over time of the packaged EL element.

Comparative Example 3 In Example 1, the EL element was prepared in the same manner as on the same side, except that a polychlorinated trifluoroethylene (PCTFE) film (thickness 250μ) with a sealant layer was used as the sealing laminated film. I sealed it.

Table 1 shows the measurement results of the moisture permeability of the sealing laminated film and the change in luminance over time of the packaged EL element.

〔Effect of the invention〕

According to the present invention described above, by employing a specific sealing method, it is possible to use a transparent laminated plastic film in which a metal oxide thin film is provided on the surface of the plastic film as the sealing film. According to the present invention, it has stable moisture-proof performance even in high-temperature areas,
It is possible to efficiently provide an organic dispersion type packaged EL element having a long life and a low decrease in brightness over time at a low cost. Therefore, the industrial value of the present invention is extremely large.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an example of a sealing film used in the present invention. FIG. 2 is a side view conceptually showing an example of a vacuum sealing machine suitably used in the sealing method of the present invention, FIG. 3 is a plan view thereof, and FIG. 4 is an explanatory diagram of a heat-sealed state. . FIG. 5 is an explanatory diagram of a state in which an EL element is sandwiched between two sealing laminated films, and FIG. 6 is an explanatory diagram of a packaged EL element obtained by the method of the present invention. FIG. 7 is an explanatory diagram of a conventionally generally employed sealing method for an EL element. In the above figure, each symbol represents the following content. (A), (B) Transparent laminated film (C)
Sealant layer (8) Insertion stage (9) Heating stage (10) Top surface (11) Bottom surface (12) Fulcrum (13), (15) Clamp (14) Flexible film (16) Substrate (17) Vacuum hole (I8) ) Reflector plate (19) Rod-shaped heater (20) Rail (21) Laminated film heating roll for EL element sealing

Claims (2)

[Claims] (1) A sealing laminated film comprising one or more transparent laminated films having a transparent thin film of metal oxide on at least one side of a transparent plastic film, and one side of which has a heat-sealable transparent sealant layer. After sandwiching the organic dispersion film type EL element between the sealant layers of these two sealing laminated films, this is placed between the flexible film and the heatable substrate, and the flexible film is placed between the flexible film and the heatable substrate. The flexible film is deformed by drawing a vacuum between the flexible film and the heatable substrate, and the sealant layers of the sealing laminated film are brought into close contact with each other by the deformation of the flexible film to perform heat sealing. An EL element sealing method characterized by: (2) At least one of the transparent plastic films forming the sealing laminated film is a polyvinyl alcohol film with a degree of saponification of 99 mol% or more, and at least one of the metal oxide thin films is a silicon-based oxide thin film. 2. The EL device sealing method according to claim 1, wherein: