JP2012018873A - El element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pasting layer having high durability, which has high adhesion strength by turning on an element while improving light extraction efficiency, reducing color shift, and having high re-workability capable of peeling off a translucent substrate.SOLUTION: An EL element 1 includes: a translucent substrate 6; a light-emitting laminated structure 5 having a light-emitting layer 4 sandwiched between an anode 2 and a cathode 3 and provided on one surface of the translucent substrate 6; an optical sheet 10 having a lens group 12 obtained by arranging a plurality of unit lenses 12 provided on one surface; and a pasting layer 20 which is constituted of a sticker or an adhesive having a light diffusion element added thereto, and pasts another surface 10a of the optical sheet 10 and another surface 6a of the translucent substrate together.

Description

  The present invention relates to an EL element (electroluminescence element) used for a flat panel display, a backlight for liquid crystal, a light source for illumination, an electric decoration, a light source for signage, and the like.

In general, an organic EL has a structure in which a light-emitting layer containing a fluorescent organic compound is sandwiched between an anode and a cathode on a light-transmitting substrate. Then, a DC voltage is applied to the anode and the cathode, electrons and holes are injected into the light emitting layer and recombined to generate excitons, and light emission when the excitons are deactivated is used. Will lead to light emission.
Conventionally, in these EL elements, when the light emitted from the light emitting layer is emitted from the light transmitting substrate, the light loss is caused by total reflection on the light transmitting substrate.

The light extraction efficiency at this time is generally said to be about 20%. For this reason, extra power is required to increase the luminance, and the deterioration of the element due to an increased load becomes a problem.
In order to improve the external extraction efficiency of light, a method has been proposed in which surface irregularities are formed on the element substrate and a light beam lost due to total reflection is extracted to the outside. In addition, a method has been proposed in which a light beam lost due to total reflection is taken out by pasting an optical sheet having a surface irregularity pattern formed on an element substrate via an adhesive or adhesive (patent) Reference 1). Thus, it becomes possible to improve light extraction efficiency by bonding the optical sheet which has surface asperity.

JP 2002-260845 A

However, depending on the shape of the surface irregularities, when the light emitting layer originally possessed by the light emitting element is a multi-layer, a large amount of light of a specific wavelength is emitted at a specific angle, resulting in a color shift that varies in color depending on the viewing angle. This will emphasize the phenomenon.
Moreover, when the film which bonded together cannot be peeled when defects, such as a foreign material mixing, generate | occur | produce in a bonding layer at the bonding process, it will be discarded together with an EL element, and will also cause a cost increase.

  The present invention has been made in view of the above circumstances, and while improving light extraction efficiency and reducing color misregistration and having high reworkability that can be peeled off from a translucent substrate, the element It is to provide a bonding layer having high adhesion strength and high durability by lighting.

  In order to solve the problem, the invention according to claim 1 includes a light emitting layered structure in which a light emitting layer is sandwiched between an anode and a cathode and provided on one surface of the translucent substrate, and a plurality of units. An optical sheet in which a lens group in which lenses are arranged is provided on one surface, and an adhesive or an adhesive to which a light diffusing element is added. The other surface of the optical sheet and the other of the translucent substrate It is an EL element characterized by having the bonding layer which bonds the surface of this.

Moreover, in the invention according to claim 2, in the description of claim 1, the bonding layer is at least two layers, and a translucent sheet is disposed between the layers, and the layers in the layers are The EL element is characterized in that the light diffusion elements have different volume ratios.
The invention according to claim 3 is the EL element according to claim 2, wherein the light-transmitting sheet is made to hold a light diffusing element.

  The invention according to claim 4 is the EL element according to claim 2 or 3, wherein the surface of the translucent sheet is subjected to a predetermined surface treatment.

  According to the present invention, it is possible to light the element while improving the light extraction efficiency and reducing the color misregistration and having high reworkability that can be peeled off between the bonding layer and the translucent substrate. It is possible to provide a bonding layer having high adhesion strength and high durability.

It is sectional drawing which shows the structure of the EL element of 1st Embodiment. It is a perspective view which shows the structure of the EL element of 1st Embodiment. It is another sectional view showing the configuration of the EL element of the first embodiment. It is sectional drawing which shows the structure of the EL element of 2nd Embodiment. It is sectional drawing which shows the structure of the EL element of 3rd Embodiment. It is a figure which shows the evaluation result of Example 1. FIG. It is a figure which shows the evaluation result of Example 2.

(First embodiment)
(Constitution)
1 and 2 show an example of the EL element of the first embodiment. 1 is a cross-sectional view, and FIG. 2 is a perspective view.
As shown in FIGS. 1 and 2, the EL element 1 includes a light-transmitting substrate 6, 7 and a light-emitting layer 4 sandwiched between the anode 2 and the cathode 3, and the light-transmitting substrate 6, 7. The light-emitting laminated structure 5 provided, the optical sheet 10 provided with a lens group in which a plurality of unit lenses are arranged on one surface, and a pressure-sensitive adhesive or adhesive to which a light diffusion element is added, And a bonding layer 20 that bonds the other surface 10a of the sheet 10 and the surface 6a of the first light-transmitting substrate 6 on which the light-emitting laminated structure 5 is not positioned.

  In the optical sheet 10, a lens group 12 is formed on a base material 11. In the lens group 12, the unit lenses 12a may be arranged in only one direction, but it is preferable that the unit lenses 12a are arranged two-dimensionally. Here, examples of the two-dimensional array include a cylindrical, orthogonal, and honeycomb array.

  The unit lens 12a has a triangular cross section. The cross-sectional shape of the unit lens 12a may be a shape other than a triangular shape, that is, a shape including a curvature. Here, the lower the curvature, the more the front luminance can be improved, but the color shift tends to become more prominent.

  As the lens group 12, a lens having adhesiveness by being cured when irradiated with active energy rays (for example, ultraviolet rays) is used when molding using an actinic radiation curable resin. For example, an ultraviolet curable photopolymer is used. Specifically, a known polymer containing an acrylic polymer, an acrylic monomer, a photoinitiator, and the like is used. A desired lens group can be obtained by curing in a pressure-bonded state with the molded plate.

  Specifically, a synthetic resin such as a polyester resin, a polyolefin resin, a polystyrene resin, a methacrylic resin, a polycarbonate resin, a vinyl chloride resin, a cycloolefin polymer, or a composite thereof is used as the substrate 11. Further, by using a thermoplastic resin, the base material 11 and the lens group 12 are integrated with each other by press-bonding a mold or a film-shaped mold provided with a desired pattern in advance during injection molding or extrusion molding to the molten resin. It can also be obtained.

  In this case, specifically, light transmission of acrylic resin, acrylonitrile resin, acrylonitrile polystyrene copolymer, polycarbonate resin, cycloolefin resin, polyester resin, styrene resin, acrylic / styrene copolymer resin, etc. Those having high properties and impact resistance can be used.

  About the bonding layer 20, any of resin systems, such as an acryl and a urethane type, may be used, and it can select suitably with the material of the base material 11 and a thermoplastic resin. More specifically, as an acrylic pressure-sensitive adhesive, a pressure-sensitive adhesive layer having excellent heat resistance can be obtained by appropriately crosslinking an acrylic polymer. As specific means of the crosslinking method, a compound having a group capable of reacting with a carboxyl group, a hydroxyl group, an amino group, an amide group, or the like, which is appropriately included as a crosslinking base point in an acrylic polymer such as an isocyanate compound, an epoxy compound, or an aziridine compound There is a method of using a so-called cross-linking agent that is added and reacted. Among these, examples of the isocyanate compound include aromatic isocyanates such as tolylene diisocyanate and xylene diisocyanate, alicyclic isocyanates such as isophorone diisocyanate, and aliphatic isocyanates such as hexamethylene diisocyanate. Among these, an epoxy compound is particularly preferably used as the isocyanate compound from the viewpoint of obtaining an appropriate cohesive force. Examples of the epoxy compound include N, N, N ′, N′-tetraglycidyl-m-xylenediamine, 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane, and the like. As the curing agent, these compounds may be used alone or in combination of two or more, and a resin system having better adhesion with a resin system at a site to be bonded can be selected.

FIG. 3 is a cross-sectional view showing an example of the EL element of the present embodiment, and is a diagram for explaining the bonding layer 20 in more detail.
As shown in FIG. 3, the bonding layer 20 includes a light diffusing element. Here, the light diffusion element is made of organic particles such as styrene resin, acrylic resin, silicone resin, urea resin, formaldehyde condensate, glass beads, silica, alumina, calcium carbonate, metal oxide, or the like. Inorganic fine particles or bubbles can be used.

  Here, the volume ratio D of the light diffusing element in the bonding layer 20 is preferably as large as possible in terms of reducing the visibility of the color shift, but in actual use, 0 <D <30% is desirable and more desirable. Is about 3 ≦ D ≦ 20%. When D <3%, it is difficult to reduce the adhesive strength of the main agent. When D> 20%, the adhesion strength starts to decrease significantly, and when D> 30%, the bonding layer 20 adheres. This is because the bonding itself is difficult because the strength is almost lost.

Moreover, when the thickness of the bonding layer 20 is S and the average diameter of the diffusion elements is T, S / 8 <T <S / 2 is desirable. This is because when T ≦ S / 8, it is difficult to impart a change to the adhesive force, and when T ≧ S / 2, it causes a floating failure during bonding.
Moreover, as thickness S of the bonding layer 20, 5 micrometers <S <50 micrometers is desirable. This is because, when S ≦ 5 μm, floating defects due to minute foreign matters frequently occur at the time of bonding, and when S ≧ 50 μm, foaming, surface roughness, etc. are caused when the adhesive is applied. This is because defects frequently occur.

Moreover, when the Hz value of the bonding layer 20 is set to Hz3, about 50% <Hz3 <95% is desirable. This is because when Hz3 ≦ 50%, there is almost no effect in reducing color misregistration, and when Hz3 ≧ 95%, the color misregistration is reduced but the light transmittance is lowered. Will be lost.
In the present embodiment, a light diffusion element that satisfies the above three conditions of D, S, and Hz is selected.

(Effects of the first embodiment)
In the present embodiment, the bonding layer 20 is added with a light diffusing element, and the conditions are appropriately selected to improve light extraction efficiency and reduce color misregistration. While having high reworkability that can be peeled off, the device is turned on to have high adhesion strength and high durability.

  For example, the bonding layer 20 has high reworkability that can be peeled off from the first light-transmitting substrate 6 within 1 hour after bonding, and in an element lighting state after entering the market. After 240 hours, it has high adhesion strength and high durability.

(Second Embodiment)
(Constitution)
FIG. 4 is a cross-sectional view showing an example of the EL element of the second embodiment.
As shown in FIG. 4, in 2nd Embodiment, the bonding layer 20 consists of two bonding layers called the 1st and 2nd bonding layers 21 and 22 at least with the same or different volume ratio of a light-diffusion element. . Here, the 1st bonding layer 21 is a bonding layer bonded with the optical sheet 11. The 2nd bonding layer 22 is a bonding layer bonded with the 1st translucent base material 6. FIG. A translucent sheet 30 is disposed between the first bonding layer 21 and the second bonding layer 22.

Here, when the adhesion strength between the first bonding layer 21 and the optical sheet 11 is F1, and the adhesion strength between the second bonding layer 22 and the first translucent substrate 6 is F2, F1> F2. Yes, if F1 <F2, the reworkability is impaired.
Moreover, when the volume ratio of the light-diffusion element of the 1st bonding layer 21 is set to D1, and the volume ratio of the light-diffusion element of the 2nd bonding layer 22 is set to D2, desirably 3% <= D1 and D2 <= 20% is there. Here, even in the case of F1 <F2, by setting D2 ≧ 3%> D1 ≧ 0%, it is possible to adjust to F1> F2 and to obtain desired reworkability. On the other hand, when F1 >> F2 and F1 >> F2 and F2 are not so different from the desired adhesion strength after a predetermined lighting time, F1 and F2 are set by D1 ≧ 3%> D2 ≧ 0%. It is possible to adjust the balance, and it is possible to obtain desired reworkability.

  Moreover, by adding more light diffusing elements to the first bonding layer 21 or the second bonding layer 22, it is possible to give a large unevenness to the surface on the arbitrary bonding side where the adhesion strength is to be lowered. Therefore, it becomes easy to balance F1> F2, and it is possible to improve reworkability while maintaining high durability.

  As the translucent sheet 30, light transmission of acrylic resin, acrylonitrile resin, acrylonitrile polystyrene copolymer, polycarbonate resin, cycloolefin resin, polyester resin, styrene resin, acrylic / styrene copolymer resin, etc. Those having high properties and impact resistance can be used. Moreover, some surface treatment may be given to the surface of these materials. The surface treatment here is a predetermined surface treatment, specifically, anchor treatment such as easy adhesion treatment, corona treatment, UV irradiation treatment, and the like, which are appropriately selected depending on the adhesion strength to be adjusted. Can do.

  Here, for example, when the adhesion strength of the interface between the first bonding layer 21 and the second bonding layer 22 is F3, when F3 <F1, F2, the reworkability is reduced. However, when the adhesion strength between the first bonding layer 21 and the translucent sheet 30 is F4 and the adhesion strength between the second bonding layer 22 and the translucent sheet 30 is F5, F4, F5> F3. When it is, reworkability can be improved. Therefore, the translucent sheet | seat 30 can be suitably selected from translucent resin by the balance of F1, F2, F4, F5. In addition, some optical sheet materials generate gas under high temperature conditions, but the second bonding layer 22 is formed from the generated gas by partitioning the bonding layer 20 into a plurality of layers (two layers in this embodiment). The effect which protects can also be expected.

(Effect of 2nd Embodiment)
In this embodiment, the bonding layer 20 consists of at least the first and second bonding layers 21 and 22, and the translucent sheet 30 is disposed between the first bonding layer 21 and the second bonding layer 22. By doing so, the bonding layer 20 improves the light extraction efficiency and reduces color misregistration, and has high reworkability that can be peeled off from the light-transmitting substrate, so that the element is lit. It has high adhesion strength and high durability.

  Furthermore, some optical sheet materials generate gas under high temperature conditions, but the gas that generated the second bonding layer 22 by partitioning the bonding layer 20 into a plurality of layers (two layers in this embodiment). We can expect effect to protect from.

(Third embodiment)
(Constitution)
FIG. 5 is a cross-sectional view showing an example of the EL element of the third embodiment.
As shown in FIG. 5, in the third embodiment, the light diffusing element is held in the translucent sheet 30.

  As the translucent sheet 30, light transmission of acrylic resin, acrylonitrile resin, acrylonitrile polystyrene copolymer, polycarbonate resin, cycloolefin resin, polyester resin, styrene resin, acrylic / styrene copolymer resin, etc. A material having high impact resistance can be used. In addition, as the light diffusing element, organic particles made of styrene resin, acrylic resin, silicone resin, urea resin, formaldehyde condensate, etc., glass beads, silica, alumina, calcium carbonate, metal oxide, etc. System fine particles or bubbles can be used.

  The translucent sheet 30 can be obtained by a melt molding method in which the light diffusing element is kneaded, or can be obtained by applying a layer to which the light diffusing element is added to the surface of the translucent substrate. Further, the surface of the translucent sheet may be subjected to some surface treatment. The surface treatment referred to here is a predetermined surface treatment, and refers to anchor treatment such as easy adhesion treatment, corona treatment, UV irradiation treatment, and the like, and can be appropriately selected depending on the adhesion strength to be adjusted.

  Thus, it becomes possible to reduce the light diffusing element added to the bonding layer 20 in order to obtain a desired Hz value by adding or applying the light diffusing element to the translucent sheet 30, that is, holding it. . As a result, bonding is performed as much as possible when the bonding material selected by the bonding material or the base material to be bonded slightly exceeds the desired bonding strength by adding a light diffusing element. By reducing the addition of light diffusing elements to the layer, it becomes possible to achieve both reworkability and adhesion strength, and by reducing the thickness of the bonding layer, it is possible to improve workability and reduce the cost of the bonding material . Further, by holding the light diffusing element in the translucent sheet 30, it is possible to obtain higher Hz compared to the case where it is added only to the bonding layer 20, and there is an advantage that the width of the element to be bonded is widened. Furthermore, it is possible to reduce the change in optical performance due to the change in the refractive index of the resin due to heat generation from the EL element 1 by imparting more light diffusion performance to the translucent sheet having a Tg higher than that of the bonding layer 20. It becomes.

(Effect of the third embodiment)
In this embodiment, it becomes possible to reduce the light-diffusion element added to the bonding layer 20 by holding the light-diffusion element in the translucent sheet 30, and the light diffusion added to the bonding layer 20 in that way. Various benefits can be gained by reducing the number of elements.

In FIG. 6, it shows about the evaluation result at the time of adding microparticles | fine-particles as a light-diffusion element to an adhesive (bonding layer).
Here, bonding layer material: acrylic adhesive, bonding layer thickness: 30 μm, light diffusion element: styrene resin cross-linked product, reliability test: 85 ° C., 85%, 500 hours. And evaluation is implemented visually and the evaluation criteria are as follows.

(1) Color misregistration visual evaluation ○: Color misregistration is less than when optical sheet is not pasted. ×: Color misregistration is the same as when optical sheet is not pasted. Immediately after floating

(3) Reworkability after bonding ○: If within 24 hours after bonding, no bonding layer remains on the translucent substrate when peeling ×: Translucent group when peeling within 24 hours after bonding (4) Reliability test ○: No lifting or peeling ×: Occurrence of lifting or peeling (5) Adhesiveness ○: 10 N or more after 240 hours of element lighting state ×: 10 N after 240 hours of element lighting state Less than

  From the evaluation results in FIG. 6, it can be seen that, for example, the reworkability is increased by increasing the average diameter and the amount of addition. Moreover, it turns out that the evaluation of an external appearance and evaluation of adhesiveness become low when an average diameter becomes large. Further, it can be seen that the color shift is reduced in a region where Hz is large.

In FIG. 7, the evaluation result at the time of adding a light-diffusion element to a translucent sheet | seat is shown.
Here, bonding layer material: acrylic adhesive, bonding layer light diffusing element: styrene resin cross-linked product, bonding layer light diffusing fine particle volume addition ratio: 3%, bonding layer light diffusing fine particle central particle size: 5 μm, first bonding layer 21 thickness: 10 μm, second bonding layer 22 thickness: 10 μm, translucent sheet material: PET, translucent sheet thickness: 20 μm, translucent sheet light diffusion element: styrene resin crosslinked product Reliability test: 85 ° C., 85%, 500 hours. And evaluation is implemented visually and the evaluation criteria are as follows.

(1) Color misregistration visual evaluation ○: Color misregistration is less than when optical sheet is not pasted. ×: Color misregistration is the same as when optical sheet is not pasted. Immediately after floating

(3) Reworkability after bonding ○: If within 24 hours after bonding, no bonding layer remains on the translucent substrate when peeling ×: Translucent group when peeling within 24 hours after bonding (4) Reliability test ○: No lifting or peeling ×: Occurrence of lifting or peeling (5) Adhesiveness ○: 10 N or more after 240 hours of element lighting state ×: 10 N after 240 hours of element lighting state Less than

  From the evaluation result of FIG. 7, it can be seen that, for example, the reworkability is increased by increasing the average diameter and the amount of addition. Moreover, it turns out that the evaluation of an external appearance and evaluation of adhesiveness become low when an average diameter becomes large. Further, it can be seen that the color shift is reduced in a region where Hz is large.

  DESCRIPTION OF SYMBOLS 1 EL element, 2 anode, 3 cathode, 4 light emitting layer, 5 light emitting laminated structure, 6, 7 translucent board | substrate, 10 optical sheet, 12 lens group, 12a unit lens, 20 bonding layers, 21 1st bonding Layer, 22 second bonding layer, 30 translucent sheet

Claims (4)

A translucent substrate;
A light-emitting laminated structure provided on one surface of the light-transmitting substrate with a light-emitting layer sandwiched between an anode and a cathode;
An optical sheet in which a lens group in which a plurality of unit lenses are arranged is provided on one surface;
It is composed of a pressure-sensitive adhesive or an adhesive to which a light diffusing element is added, and a bonding layer that bonds the other surface of the optical sheet and the other surface of the translucent substrate,
An EL element comprising: The bonding layer is at least two layers, and a translucent sheet is disposed between the layers,
The EL device according to claim 1, wherein volume ratios of the light diffusing elements in the respective layers are different.   The EL device according to claim 2, wherein a light diffusing element is held on the translucent sheet.   The EL element according to claim 2, wherein the surface of the translucent sheet is subjected to a predetermined surface treatment.

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