JP6735554B2 - Flexible organic EL display device and manufacturing method thereof - Google Patents

Description

The present invention relates to a flexible organic EL display device and a method for manufacturing the same.

In the manufacture of a flexible organic EL display device, after forming an organic EL display panel, various resin films are placed on the organic EL display panel. For example, a resin film such as a polarizing film or a retardation film is placed on the substrate of the organic EL display panel. At this time, the substrate of the organic EL display panel and the resin film or the resin films are generally joined together by using an adhesive (for example, a pressure-sensitive adhesive).

The flexible organic EL display device is excellent in flexibility and may be used in a bent state, or may be rolled and transported or stored, and thus is often exposed to bending stress. When repeatedly exposed to bending stress, the adhesive layer used for bonding (hereinafter, referred to as “adhesive layer”) becomes cloudy and display characteristics may deteriorate. It is believed that this is because bending stress causes voids to occur in the adhesive layer, causing light scattering. Therefore, a flexible organic EL display device requires a bonding method that does not use an adhesive agent that causes clouding.
As a joining method that does not use an adhesive, Patent Document 1 proposes performing surface activation treatment using plasma.

JP, 2005-347204, A

However, in the production of the flexible organic EL display device, the functional groups on the joint surfaces of the adjacent resin films do not sufficiently react with each other only by performing the surface activation treatment using plasma (that is, the joint surface of the adjacent resin films is not reacted). Therefore, there is a problem that it is not possible to firmly bond the adjacent resin films because the chemical bonds between the functional groups of (1) are not sufficiently obtained.
The present invention has been made to solve the above problems, and by firmly bonding between adjacent resin films without using an adhesive, it is possible to be repeatedly exposed to bending stress. An object of the present invention is to provide a flexible organic EL display device capable of preventing white turbidity and a manufacturing method thereof.

As a result of continuing intensive research to solve the above problems, the present inventors have performed surface activation treatment on adjacent resin films, and then pressurizing them while heating to firmly and directly bond the adjacent resin films. The inventors have found that it can be done and have completed the present invention.
That is, the present invention is a flexible organic EL display device having a laminated structure in which at least two resin films are adjacent to each other, wherein the adjacent resin films are directly bonded. Is.
In addition, the present invention is a method for manufacturing a flexible organic EL display device having a laminated structure in which at least two resin films are adjacent to each other, wherein the at least two resin films are subjected to surface activation treatment and then pressurized while being heated. It is a method for manufacturing a flexible organic EL display device, which is characterized in that it is directly bonded.

According to the present invention, a flexible organic EL display capable of preventing clouding due to repeated exposure to bending stress by firmly bonding between adjacent resin films without using an adhesive. An apparatus and a manufacturing method thereof can be provided.

It is sectional drawing of the flexible organic EL display device of embodiment of this invention. It is sectional drawing of the flexible organic EL display device of another embodiment of this invention. It is sectional drawing of the flexible organic EL display device of another embodiment of this invention. 7 is a graph showing changes in transmittance with respect to the number of times the bending test is repeated in Examples. It is a graph which shows the change of the haze value with respect to the number of repetitions of a bending test in an example.

The flexible organic EL display device of the present invention has a laminated structure in which at least two resin films are adjacent to each other, and the adjacent resin films are directly bonded to each other. The flexible organic EL display device of the present invention having such characteristics can be manufactured by subjecting at least two resin films to surface activation treatment and then applying pressure while heating.
Here, in the present specification, the “resin film” is a concept including a resin substrate, sheet, film, layer, plate and the like, and the type thereof is not particularly limited.
Preferred embodiments of the flexible organic EL display device and the manufacturing method thereof according to the present invention will be described below with reference to the drawings. In the following embodiments, a bottom emission type flexible organic EL display device will be described as an example, but it goes without saying that it is also applicable to a top emission type flexible organic EL display device.

FIG. 1 is a sectional view of a flexible organic EL display device of the present invention. In FIG. 1, the flexible organic EL display device 1 has an organic EL display panel 2 and a polarizing film 4 formed on a substrate 3 of the organic EL display panel 2. In the flexible organic EL display device 1 having this laminated structure, the substrate 3 and the polarizing film 4 correspond to resin films.
The organic EL display panel 2 is not particularly limited as long as the substrate 3 is made of resin, and one having a structure known in the art can be used. Generally, the organic EL display panel 2 has an organic EL element (not shown), a color filter (not shown), etc. in addition to the substrate 3.

The substrate 3 made of resin is not particularly limited, and those known in the art can be used. As the resin constituting the substrate 3, a polyester resin such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene terephthalate (PBT); polyethylene (PE), polypropylene (PP), polymethylpentene (PMP) , Ethylene-propylene copolymer, ethylene-vinyl acetate copolymer (EVA) and other olefin resins containing α-olefin as a monomer component; polyvinyl chloride (PVC); vinyl acetate resin; polycarbonate (PC); polyphenylene Sulfide (PPS); amide-based resin such as polyamide; polyimide-based resin; flexible synthetic resin such as polyether ether ketone (PEEK). Among them, the substrate 3 is preferably a polyimide substrate excellent in various characteristics such as heat resistance.

The polarizing film 4 is not particularly limited as long as it is made of resin, and a known film in the technical field can be used. Examples of the polarizing film 4 include a film in which an iodine compound is adsorbed and oriented in polyvinyl alcohol (PVA). Moreover, the polarizing film 4 may be a laminated body of a plurality of films.

It is usually necessary to bond the substrate 3 and the polarizing film 4 with an adhesive, but the adhesive layer formed between the substrate 3 and the polarizing film 4 is repeatedly exposed to bending stress. Then, it becomes cloudy and the display characteristics deteriorate.
Therefore, in the present invention, the substrate 3 and the polarizing film 4 are directly joined by a joining method that does not use an adhesive that causes white turbidity. That is, after subjecting the bonding surfaces of the substrate 3 and the polarizing film 4 to surface activation treatment, respectively, the substrate 3 and the polarizing film 4 are overlapped and pressed while being heated so that the substrate 3 and the polarizing film 4 are directly bonded. There is.

The surface activation treatment is not particularly limited as long as it is a treatment capable of generating a functional group having a hydroxyl group (for example, a COH group or a COOH group) on the bonding surface between the substrate 3 and the polarizing film 4. Note that this surface activation treatment is also referred to as hydrophilic treatment.
Examples of the surface activation treatment include a method using extreme ultraviolet (EUV) and plasma.
For example, when the surface activation treatment is performed using extreme ultraviolet rays, the bonding surface between the substrate 3 and the polarizing film 4 may be irradiated with extreme ultraviolet rays. The extreme ultraviolet irradiation conditions may be appropriately set according to the extreme ultraviolet irradiation device used and are not particularly limited.
In the case where the surface activation treatment is performed using plasma, plasma may be applied to the bonding surfaces of the substrate 3 and the polarizing film 4 in a gas atmosphere of nitrogen, oxygen, argon, or the like or a vacuum atmosphere. The plasma irradiation conditions may be set appropriately according to the plasma generator used and are not particularly limited.

The heating temperature may be set according to the materials of the substrate 3 and the polarizing film 4 and the type of surface activation treatment, and is not particularly limited. The heating temperature is generally 40°C to 200°C, preferably 45°C to 170°C, and more preferably 50°C to 150°C. Further, although it depends on the type of the organic EL display panel 2, the heating temperature is particularly preferably 90° C. or lower from the viewpoint of preventing deterioration of the organic EL element due to heat.

The pressing force may be set according to the materials of the substrate 3 and the polarizing film 4 and the type of surface activation treatment, and is not particularly limited. The applied pressure is generally 0.05 MPa to 5 MPa, preferably 0.1 MPa to 4 MPa, more preferably 0.2 MPa to 3 MPa. Further, although it varies depending on the type of the organic EL display panel 2, the applied pressure is particularly preferably 0.5 MPa or less from the viewpoint of preventing the organic EL element from being destroyed by pressure.
The pressurizing method is not particularly limited, and a method known in the art can be used. For example, it may be performed using a pressure roll or the like that is generally used in laminating.

When the substrate 3 and the polarizing film 4 are stacked and pressed while heating as described above, the functional groups generated on the bonding surfaces of the substrate 3 and the polarizing film 4 chemically bond (preferably covalently bond), and the substrate 3 And the polarizing film 4 are firmly and directly bonded.
In the present invention, since the substrate 3 and the polarizing film 4 are directly bonded to each other without using an adhesive, it is possible to prevent clouding due to repeated exposure to bending stress. Further, in the present invention, since the adhesive layer can be reduced, the thickness of the flexible organic EL display device 1 can be reduced.

FIG. 2 is a cross-sectional view of the flexible organic EL display device 1 of the present invention further having a retardation film 5 between the substrate 3 and the polarizing film 4.
In the flexible organic EL display device 1 having such a structure, the substrate 3 and the retardation film 5 and the retardation film 5 and the polarizing film 4 are directly joined by the joining method described above. There is.
The retardation film 5 is not particularly limited as long as it is made of resin, and those known in the art can be used. Examples of the retardation film 5 include those obtained by stretching a film formed of a polycarbonate resin or a cycloolefin resin. Further, the retardation film 5 may be a laminate of a plurality of films.

FIG. 3 is a cross-sectional view of the flexible organic EL display device 1 of the present invention further having a barrier film 6 between the substrate 3 and the retardation film 5.
In the flexible organic EL display device 1 having such a structure, between the substrate 3 and the barrier film 6, between the barrier film 6 and the retardation film 5, and between the retardation film 5 and the polarizing film 4, It is directly joined by the joining method described above.
The barrier film 6 is not particularly limited as long as the bonding surface is made of resin, and any known film in the technical field can be used. For example, the barrier film 6 in which a barrier layer or the like is formed on a base material such as PET or PEN can be used.

In the above-described embodiment, the case where the resin film is the substrate 3, the polarizing film 4, the retardation film 5, and the barrier film 6 has been described as an example, but it is also applicable when various other resin films are used. Needless to say.

The following experiments will explain the present invention in detail, but the present invention is not limited thereto.
(Preparation of sample A)
After performing plasma treatment on one side of two PET films (1.0 in (2.54 cm) x 21 cm x 50 µm) in a gas (oxygen gas, argon gas or mixed gas of oxygen and argon) atmosphere, the plasma treated surface They were superposed and bonded by applying a pressure of 2 MPa while heating to a temperature of 150°C.
(Production of Sample B)
After irradiating extreme ultraviolet rays on one side of two PET films (1.0 in×21 cm×50 μm), superimpose the sides irradiated with extreme ultraviolet rays and pressurize at a pressure of 0.3 MPa while heating to a temperature of 70° C. Joined by.
(Preparation of sample C)
Two PET films (1.0 in x 21 cm x 50 μm) were joined using a commercially available pressure sensitive adhesive. The layer of pressure sensitive adhesive between the PET films was 25 μm.

Each sample obtained above was subjected to a peel test at 180°C using a tensile tester.
As a result, the peel strength of Sample C was 1.3 kgf/in, and peeling at the layer portion of the pressure sensitive adhesive was confirmed. On the other hand, in Samples A and B, peeling at the joint was not confirmed, and when the peel strength was increased, the PET film was broken.

Next, a bending test was performed on Samples A and C. The bending test was repeated 10,000 times under the conditions of radius of curvature R2 mm, R5 mm and R30 mm. Then, changes in the transmittance, the haze value, and the peel strength with respect to the number of repetitions of the bending test were evaluated. The haze value and the transmittance were measured with a spectrophotometer (CM1000 manufactured by Konica Minolta Co., Ltd.) under the conditions of C light source and wavelength range of 380 nm to 780 nm.

The rate of change in the transmittance and the haze value with respect to the number of repetitions of the bending test are shown in FIGS. 4 and 5, respectively. In FIGS. 4 and 5, PAS R30 means sample C which was subjected to the bending test under the condition of radius of curvature R30 mm, PAS R5 means sample C which was subjected to the bending test under the condition of radius of curvature R5 mm, and PAS R2 indicates the curvature This means Sample C that was subjected to a bending test under the condition of a radius R2 mm. In addition, Less R30 is a sample A that has been subjected to a bending test under the condition of a radius of curvature R30 mm, Less R5 is a sample A that has been subjected to a bending test under the condition of a radius of curvature R5 mm, and Less R2 is a bending test under the condition of a radius of curvature R2 mm. It means sample A which was subjected to.
Table 1 shows the change in peel strength with respect to the number of repetitions of the bending test.

As shown in FIG. 4, in Samples A and C, a large change in transmittance with respect to the number of times the bending test was repeated was not confirmed. Further, as shown in Table 1, sample A had a larger peel strength with respect to the number of times of repeating the bending test, as compared with sample C. Further, the haze value with respect to the number of repetitions of the bending test was not particularly changed in the sample A, but was large when the number of repetitions was 10,000 in the sample C subjected to the bending test under the condition of the radius of curvature R5 mm or R2 mm. changed.

As can be seen from the above results, according to the present invention, it is possible to prevent clouding due to repeated exposure to bending stress by firmly bonding between adjacent resin films without using an adhesive. It is possible to provide a flexible organic EL display device and a manufacturing method thereof.

1 flexible organic EL display device, 2 organic EL display panel, 3 substrate, 4 polarizing film, 5 retardation film, 6 barrier film.

Claims (3)

A method of manufacturing a bottom emission type flexible organic EL display device having a laminated structure in which at least two resin films are adjacent to each other,
It said at least two resin film arm has a resin substrate of the organic EL panel, and a polarizing film is bonded directly to the lower surface of the resin substrate, one of the retardation film and the barrier film ,
After surface-activating one of the resin substrate, the polarizing film, the retardation film and the barrier film, they are directly bonded by pressing while heating ,
Method of manufacturing a flexible organic EL display device applied pressure, characterized in der Rukoto below 0.5 MPa. The method of manufacturing a flexible organic EL display device according to claim 1 , wherein the surface activation treatment is performed using extreme ultraviolet rays or plasma. Method of manufacturing a flexible organic EL display device according to claim 1 or 2 heating temperature is equal to or is 90 ° C. or less.

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