JP2007157343A - El panel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electroluminescent (EL) panel capable of providing stable light emission characteristics. <P>SOLUTION: The EL panel 10 of a preferred embodiment is configured to include a substrate 2, an EL element 4, a protection layer 6 covering the EL element 4, and a sealing plate 8 that are stacked in this order. The protection layer 6 is entirely formed of a curable resin having a cure degree of 30% to 70%. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an EL panel in which an EL element is protected by being covered with a protective layer made of a resin.

  EL elements such as organic EL (ElectroLuminescence) and inorganic EL are self-luminous light-emitting elements that have high brightness and are easy to reduce in size and weight, and can be applied to displays and lighting. Is expected. However, the light emitting material used for these EL elements tends to be deteriorated by the outside air (especially moisture such as moisture), and this is one factor that hinders the life of the elements. For this reason, the EL element is conventionally used in the form of an EL panel in which the element is sealed in order to reduce contact with outside air.

  As a form of such sealing, a hollow type sealing in which an EL element is disposed between a substrate and a sealing plate and only the outer peripheral portion is closed with a sealing agent made of resin or the like is known. However, in this hollow type sealing, it is often necessary to introduce a desiccant or the like inside to completely remove the moisture in the hollow portion, and it tends to be difficult to reduce the size and thickness of the EL panel. It was in.

  Therefore, in order to reduce such inconvenience, the solid sealing type in which the entire region including the EL element between the substrate and the sealing plate is not hollowed and is filled with a curable resin to form an adhesive layer. The structure of is known. In this case, since the periphery of the EL element is completely sealed, it is difficult for moisture to enter and remain, and the introduction of a desiccant becomes unnecessary. As a material for forming such an adhesive layer, a heat or photo-curing type epoxy resin that has a property of being able to satisfactorily bond the substrate and the sealing plate and having low moisture permeability is used.

  However, the solid-sealed EL panel using an epoxy resin for the adhesive layer as described above has a problem that the light emission characteristics are likely to be gradually deteriorated. This is considered to be one factor that the epoxy resin is usually extremely hard when cured, and that stress generated during the curing reaction or the like is easily retained as internal stress after curing. If the cured product of the epoxy resin constituting the adhesive layer has internal stress, the EL element in close contact with the adhesive layer is damaged and destroyed by the internal stress. As a result, the light emitting area of the EL panel Becomes smaller.

Therefore, in order to reduce the deterioration of the light emission characteristics due to such destruction of the EL element, the following Patent Document 1 discloses a solid-sealing type structure of a curable resin (adhesive resin) constituting the adhesive layer. An EL panel (display device) is disclosed in which the outer peripheral portion is cured and all or part of the peripheral portion of the EL element is uncured. In such an EL panel, since the adhesive layer in contact with the EL element is uncured and flexible, the stress is easily relieved, and the EL element is not easily broken by the stress of the adhesive layer.
JP 2003-197366 A

  However, even when the configuration as in the above prior art is adopted, it is still difficult to sufficiently suppress the deterioration of the light emission characteristics of the EL panel over time.

  Therefore, the present invention has been made in view of such circumstances, and an object thereof is to provide an EL panel capable of obtaining stable light emission characteristics.

  When the present inventors examined the solid-sealed EL panel having the above-described configuration of the prior art, even when the periphery of the EL element in the adhesive layer is wholly or partially uncured, the EL element It has been found that it may be difficult to suppress a decrease in the light emission area. That is, even when the adhesive layer is uncured, if the degree of curing is high, the internal stress cannot be sufficiently relaxed, so that it is difficult to suppress the destruction of the EL element. On the other hand, when the degree of cure is extremely small, such as when the adhesive layer is not cured at all, the adhesion to the substrate and the sealing plate becomes insufficient, and the outside air enters from these and the EL element is damaged. As a result, the light emitting area of the EL element is reduced.

  The present invention has been made based on such knowledge, and by applying a curable resin having a predetermined degree of curing as a material for protecting the EL element, the reduction of the light emitting area can be more reliably reduced. As a result, the present invention has been completed.

  That is, the EL panel of the present invention includes a substrate, an EL element provided on the substrate, and a protective layer provided on the substrate so as to cover the EL element, and the protective layer is 30 to 70%. The whole is constituted by a curable resin having a curing degree.

  Here, the degree of cure of the curable resin is an index of curing progress obtained by removing temperature dependence from an ionic viscosity curve derived from dielectric loss obtained by dielectric analysis (DEA analysis) of the curable resin, This is a value obtained by converting the time when the ion viscosity curve becomes flat as the curing degree 100% (complete curing).

  Thus, in the EL panel of the present invention, the EL element has a degree of cure of 30 to 70% and is sealed with a protective layer made of a curable resin that is not completely cured. Since such a protective layer has appropriate flexibility, it can easily relieve stress generated during curing. Therefore, in the EL panel of the present invention, although the EL element is in close contact with the protective layer made of a curable resin, the EL element is hardly broken due to the internal stress of the protective layer.

  In the EL panel of the present invention, as described above, the entire protective layer is made of a curable resin having a curing degree of 30 to 70%. Here, according to the study by the present inventors, the curable resin becomes a dense structure as the curing progresses and it is difficult to pass components such as moisture. It was found that moisture and other components can be easily passed. This is not necessarily clear, but is considered to be caused by the fact that a large number of gaps through which gas or the like passes are formed in the resin structure due to an increase in the ratio of the crosslinked structure in the curable resin.

  In the EL panel having the configuration described in Patent Document 1, the portion of the adhesive layer that comes into contact with the outside air is completely cured, and this portion has a structure that allows easy passage of external moisture or the like as described above. In contrast, the entire protective layer of the EL panel of the present invention is completely cured on the outer peripheral portion as described above because it is entirely composed of an uncured (30 to 70% curing degree) curable resin. Compared to an adhesive layer having a different portion, it is more difficult to pass components such as moisture. As a result, the EL panel of the present invention can also effectively suppress a decrease in light emission characteristics due to the deterioration of the light emitter due to the intrusion of external moisture or the like.

  The curable resin constituting the protective layer may have a different degree of curing in the protective layer as long as it is in the range of 30 to 70%. preferable. This makes it possible to relieve the stress more uniformly and reduce the damage to the EL element particularly well.

  In the above-mentioned EL panel of the present invention, the curable resin constituting the protective layer has a curing degree of 30 to 70%, and when completely cured (when the curing degree is 100%) ) The glass transition temperature (Tg) is preferably 100 ° C or higher. Usually, the resin material has a tendency to rapidly reduce the adhesion to a predetermined substrate at a temperature equal to or higher than its Tg. On the other hand, since the curable resin in the present invention has a Tg exceeding the normal environmental temperature assumed at the time of manufacturing and using the EL panel, it can maintain good adhesion to the substrate. As a result, in the EL panel of the present invention, the protective layer is hardly peeled off, and the EL element is hardly broken or deteriorated due to the peeling.

  According to the present invention, it is possible to provide an EL panel capable of obtaining stable light emission characteristics over a long period of time.

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

  FIG. 1 is a diagram schematically showing a cross-sectional configuration of an EL panel according to a preferred embodiment. As shown in the figure, the EL panel 10 is opposite to the substrate 2, the EL element 4 formed on the substrate 2, the protective layer 6 formed on the substrate 2 so as to cover the EL element 4, and the substrate 2. And a sealing plate 8 disposed so as to sandwich the protective layer 6. In the present embodiment, an EL panel 10 having a top emission type structure in which light emitted from the EL element 4 is extracted from the sealing plate 8 side will be described.

  The substrate 2 also serves as a substrate in the EL element 4 and can be applied without particular limitation as long as it is normally used as a substrate for an EL element. Examples of the constituent material of the substrate 2 include a glass substrate, a silicon substrate, a film substrate, an organic substrate typified by a resin substrate, and the like. The sealing plate 8 is made of a transparent material capable of taking out light emitted from the EL element 4, and examples thereof include those made of glass or plastic material.

  As the EL element 4, both an organic EL element and an inorganic EL element can be applied. In particular, the organic EL element is applied to an EL panel having a sealing structure as in this embodiment because the organic material constituting the light emitter tends to deteriorate due to moisture contact due to external moisture or the like. It is effective to do.

  The protective layer 6 is sandwiched between the substrate 2 and the sealing plate 8 and has a structure including the EL element 4 therein. The protective layer 6 is made of a curable resin, and the curable resin has a degree of cure of 30 to 70%. Here, if the degree of cure of the curable resin constituting the protective layer 6 is less than 30%, the adhesiveness with the substrate 2 or the sealing plate 8 becomes insufficient, and external air or the like enters from the interface with them. By doing so, the EL element 4 in the EL panel 10 is easily damaged. On the other hand, when the degree of cure exceeds 70%, it becomes easy for the protective layer 6 to retain the stress generated during curing as internal stress, and the internal stress is applied to the EL element 4 so that the EL element 4 is damaged. It comes to occur. From the viewpoint of more surely avoiding these disadvantages, the degree of cure of the curable resin constituting the protective layer 6 is preferably 40 to 60%.

  As curable resin which comprises the protective layer 6, photocuring resin or thermosetting resin is mentioned. In addition, since the resin here is a compound having the above-mentioned degree of curing, a monomer component that is a component before polymerization of the resin, or an oligomer component or a polymer component obtained by polymerizing these components is mixed. It is.

  Examples of the photocurable resin include both a photo radical curable resin and a photo cation curable resin. Moreover, as a thermosetting resin, an epoxy resin, a silicone resin, etc. are mentioned, The adhesiveness with the board | substrate 2 and the sealing board 8 is favorable, and also an epoxy resin is more preferable from moisture permeability being low. Of the photocurable resin and the thermosetting resin, the photocurable resin is more preferable because the degree of curing is easily adjusted to the above range.

  Examples of the photo-radical curable resin include acrylic resins, and examples thereof include acrylated epoxy resins, acrylated polyurethanes, and acrylic resins. Examples of the photo cation curable resin include a photo cation curable epoxy resin. For example, an epoxy resin such as an alicyclic epoxy resin, a bisphenol epoxy resin, a novolac epoxy resin, or the like as a main component, a diazonium compound, a sulfonium compound, or an iodonium. The thing which combined photocationic catalysts, such as a compound, can be illustrated.

  Among the photocurable resins described above, a photocationic curable epoxy resin is particularly preferable because it can easily adjust the degree of curing and has excellent stress relaxation properties. Specific examples of the photocation curable resin include UV cation curable epoxy resins XNR5570 and XNR5516 manufactured by Nagase ChemteX Corporation, and 30Y-437W manufactured by ThreeBond Co., Ltd.

  The curable resin constituting the protective layer 6 preferably has a Tg of 100 ° C. or higher when completely cured, and more preferably 110 ° C. or higher. More preferably, it is 120-140 degreeC. Here, Tg when completely cured is Tg when the above-described degree of curing is 100%, and for example, a value calculated by measurement using a suggested scanning calorimeter (DSC) is adopted. be able to. When the Tg of the curable resin is less than 85 ° C., for example, when the EL panel 10 is exposed to a high temperature environment during manufacture or use, the adhesiveness of the protective layer 6 is reduced and the substrate 2 or the sealing plate In some cases, the protective layer 6 may peel off from 8.

  Next, a preferred method for manufacturing the EL panel 10 having the above-described configuration will be described.

  First, the substrate 2 is prepared, and the EL element 4 is formed thereon. Subsequently, a curable resin (a composition containing a monomer component and a curing agent) before curing is applied on the substrate 2 by a spin coating method or the like, and a layer made of a curable resin is formed so that at least the EL element 4 is covered. To do. Then, the sealing plate 8 is bonded to the substrate 2 through a layer made of a curable resin. In addition, when the curable resin layer is formed between the substrate 2 and the sealing plate 8 by simply bonding the sealing plate 8 after dropping the curable resin on the substrate 2, the above-described case is used. It is not always necessary to apply a curable resin.

  Then, the structure obtained in this manner is heated or irradiated with actinic rays according to the type of the curable resin, and the curable resin is cured until the degree of cure becomes 30 to 70% to protect the structure. 6 is obtained to obtain the EL panel 10 having the structure shown in FIG. Specifically, first, when the curable resin is a thermosetting resin, the curable resin is cured by heating the structure. At this time, the heating is preferably performed at a temperature at which the EL element 4 (particularly the light emitter) is not deteriorated.

  On the other hand, when the curable resin is a photocurable resin, actinic rays are irradiated from the sealing plate 8 side that can transmit light in the structure. Here, an actinic ray is a ray having energy that can cause a polymerization reaction of a photocurable resin, and examples thereof include ultraviolet light (UV). As the ultraviolet light, for example, light emitted from a high-pressure mercury lamp can be used.

  In the curing of the curable resin, the degree of curing is set in the range of 30 to 70% by adjusting the conditions of heating and irradiation with actinic rays. Specifically, in the case of heating, the heating temperature and the heating time are adjusted. In the case of irradiation with actinic rays, the irradiation amount and irradiation time of light rays, and the temperature during light irradiation are adjusted. As these conditions, it is possible to apply the conditions when the degree of cure is measured in advance under various conditions using the same curable resin and a degree of cure of 30 to 70% is obtained.

  The degree of cure of the curable resin can be measured by dielectric analysis (DEA analysis) using the curable resin. Specifically, first, a curable resin is disposed between a pair of electrodes, an alternating voltage is excited on one electrode, and a change in the phase and amplitude of the response of the other electrode obtained thereby results in a permittivity and a dielectric. Calculate the dielectric properties of the loss. An ion viscosity curve, which is a parameter of ion movement independent of frequency, is derived from the dielectric loss value thus obtained. And the curve which shows the change of a cure degree can be calculated | required by remove | excluding temperature dependence from this ion viscosity change. And the value of hardening degree can be calculated | required by converting the point where the ionic viscosity curve obtained above became flat as hardening degree 100%. Such dielectric analysis can be performed using, for example, a DEA system (DEA230, DEA231) manufactured by NETZSCH.

Examples of suitable conditions for setting the degree of cure of the curable resin to 30 to 70% include the following conditions. That is, when the curable resin is a thermosetting epoxy resin, heating is performed at a temperature of about 80 ° C. for about 30 minutes to 2 hours, or heating is performed at a temperature of about 100 ° C. for about 30 minutes to 2 hours. It is preferable. On the other hand, when the curable resin is a photocationic curable epoxy resin, UV irradiation may be performed at an irradiation amount of 12000 mJ / cm ² , and after photocuring, heating may be performed at 80 ° C. for about 1 hour for further heat curing. preferable.

  As described above, the EL panel and the manufacturing method thereof according to the preferred embodiment of the present invention have been described. However, the present invention is not limited to the above-described embodiment, and can be appropriately changed without departing from the spirit of the present invention.

  First, in the EL panel 10 described above, the sealing plate 8 is disposed on the protective layer 6. However, the sealing plate 8 is not always necessary, and the EL element 4 can be sufficiently protected only by the protective layer 6. The sealing plate 8 may not be provided. The EL panel 10 has a top emission type configuration, but may be a bottom emission type EL panel in which light is extracted from the substrate 2 side by configuring the substrate 2 from a transparent material, for example. In this case, what is necessary is just to replace the constituent material of the board | substrate 2 and the sealing plate 8 with the case in embodiment mentioned above.

  Furthermore, although the EL panel 10 having the minimum configuration is illustrated in the above embodiment, the EL panel may further have another configuration as necessary. For example, when an EL panel is used for a display or the like, a color filter may be provided on the sealing plate 8 side so that the panel can be colored.

  Furthermore, in the above-described EL panel manufacturing method, the curable resin is cured after the sealing plate 8 is bonded to the substrate 2, but the present invention is not necessarily limited to this, and the bonding of the sealing plate 8 is not cured. It may be performed after curing of the functional resin, or may be performed while curing. However, from the viewpoint of ensuring good adhesiveness, it is preferable that the sealing plate is bonded before the curable resin is cured.

EXAMPLES Hereinafter, although an Example demonstrates this invention still in detail, this invention is not limited to these Examples.
[Example 1]

(Production of EL panel)
First, an organic EL element was formed on the substrate. Next, a UV cation curable epoxy resin (XNR5570, manufactured by Nagase ChemteX Corporation), which is a curable resin, was dropped onto the substrate. Then, a transparent sealing plate was attached to the substrate so as not to contact the element from the EL element side. Thus, an EL element was disposed between the substrate and the sealing plate, and a structure having a structure in which the curable resin was filled between the substrate and the sealing plate was obtained. In Example 1, five such structures were prepared.

  Then, UV irradiation was performed on the five structural bodies from the sealing plate side with an integrated light amount of 10%, 30%, 50%, 70%, and 90%, respectively, to cure the curable resin. . Thus, five types of EL panels having the structure shown in FIG. 1 and different in the degree of curing of the curable resin constituting the protective layer were obtained.

(Measurement of change in emission area over time)
Using each of the obtained EL panels, a light emission test was performed to measure a decrease in the light emitting area after a predetermined time elapsed. That is, first, the EL panel immediately after manufacture was caused to emit light, and the area of the light emitting region was measured. Then, the EL panel was allowed to stand at 60 ° C. and 95% RH, and the area of the light emitting region after 80 hours and 160 hours was measured in the same manner. And the area of the light emission area | region in each time passage when the area of the light emission area | region immediately after manufacture was set to 100 was calculated | required. The obtained results are shown in FIG.

  FIG. 2 is a graph showing the change over time of the light emission area in each EL panel of Example 1. In FIG. 2, L11, L12, L13, and L14 show the results obtained with the EL panel including a protective layer made of a curable resin having a curing degree of 10%, 30%, 50%, and 70%, respectively. In addition, in the EL panel in which the protective layer is a curable resin having a curing degree of 90%, the EL element was destroyed immediately after production, and light emission could not be observed.

From FIG. 2, in the EL panel having a protective layer made of a curable resin having a curing degree of 30%, 50% and 70%, the light emitting area was hardly decreased even after 160 hours, whereas the curing degree It was found that in the EL panel in which 10% is 10%, the light emitting area decreases according to the elapsed time.
[Example 2]

(Production of EL panel)
10%, 30%, 50%, and 70, respectively, in the same manner as in Example 1 except that epoxy acrylate, which is a photo radical curable resin, was used as the curable resin instead of the UV cation curable epoxy resin. Five types of EL panels provided with a protective layer made of a curable resin having a degree of cure of 90% and 90% were prepared.

(Measurement of luminescence characteristics over time)
The change over time of the light emission characteristics of each EL panel was measured in the same manner as in Example 1 except that the measurement time of the light emitting area was 40 hours, 70 hours, and 120 hours, respectively. The obtained results are shown in FIG.

  FIG. 3 is a graph showing the change over time of the light emission area in each EL panel of Example 2. In FIG. 2, L21, L22, L23, and L24 show the results obtained with an EL panel including a protective layer made of a curable resin having a curing degree of 10%, 30%, 50%, and 70%, respectively. In addition, in the EL panel in which the protective layer is a curable resin having a curing degree of 90%, the EL element was destroyed immediately after production, and light emission could not be observed.

  As shown in FIG. 3, the EL panel including a protective layer made of a curable resin having a curing degree of 30%, 50%, and 70% has a light emission over time as compared with an EL panel having a curing degree of 10%. It was confirmed that the area reduction was extremely small.

It is a figure which shows typically the cross-sectional structure of the EL panel which concerns on suitable embodiment. 3 is a graph showing a change with time of a light emitting area in each EL panel of Example 1. FIG. 10 is a graph showing a change with time of a light emission area in each EL panel of Example 2.

Explanation of symbols

  2 ... substrate, 4 ... EL element, 6 ... protective layer, 8 ... sealing plate, 10 ... EL panel.

Claims (3)

A substrate, an EL element provided on the substrate, and a protective layer provided on the substrate so as to cover the EL element,
The protective layer is entirely composed of a curable resin having a degree of curing of 30 to 70%.
An EL panel characterized by that.   2. The EL panel according to claim 1, wherein the curable resin has a degree of cure of 30 to 70% and has substantially the same degree of cure throughout the protective layer.   2. The EL panel according to claim 1, wherein the curable resin has a degree of curing of 30 to 70%, and has a glass transition temperature of 100 ° C. or higher when completely cured.

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