1. Field of the Invention
The present invention relates to an electroluminescence (EL) device and, particularly, to a sealing structure for an EL device.
2. Description of Related Art
Generally, the term electroluminescence element (EL element) is used to refer to a single element, while the term electroluminescence device (EL device) refers to a device including one or more EL elements arranged on a substrate. In EL elements, the substances used for the emissive layer are commonly classified into inorganic compounds and organic compounds. The former substance is used in inorganic EL elements, while the latter substance is used for producing organic EL elements.
FIG. 1 shows the configuration of a conventional EL device. In the EL device 200 shown in FIG. 1, plurality of first electrodes 12 are formed in the emissive area of a substrate 10 formed from, for example, a glass substrate. An emissive element layer 16 composed of an inorganic or organic compound is formed over the first electrodes 12. A single second electrode 14 is formed on the emissive element layer 16. Thus, an emissive element substrate 18 is formed of the substrate 10, the first electrodes 12, the emissive element layer 16, and the second electrode 14.
The first electrode 12 is an electrode (anode) made of a transparent conductive material, e.g. ITO (Indium Tin Oxide). The second electrode is a metal electrode (cathode).
The sealing member 42 covers the open region above the second electrode 14 of the emissive element substrate 18 so as to form a gap 30 between the second electrode 14 and the sealing member 42. The ends of the sealing member 42 are adhered to the emissive element substrate 18 using a resin material. In order to prevent deterioration of an emissive element which can be caused by absorption of moisture, an inert gas, such as nitrogen, or silicone oil is introduced into the gap 30 under a reduced pressure.
In the emissive element layer 16 of the EL device 200, holes are injected from the first electrode 12 while electrons are injected from the second electrode 14. The holes and electrons thus injected move through the emissive element layer 16, collide with each other, and recombine. When holes and electrons recombine, they disappear, but the energy generated by their recombination excites luminous molecules, thus causing light emission.
In the conventional EL element or EL device 200 shown in FIG. 1, because the gap 30 is provided between the second electrode 14 and the sealing member 42, an externally applied mechanical vibration or shock may deform the sealing member 42 in the direction of the second electrode 14. As a result, the sealing member 42 may collide with the second electrode 14, thus damaging the second electrode 14 or the emissive element forming layer 16.
Before the EL device is shipped, it is adjusted under a pressure of, for example, 5 Pa. When this is done, the sealing member 42 may deform and damage the organic EL element. Such damage to the organic EL element may cause dark spots and hasten the deterioration of the EL organic element, thus resulting in decreased display quality or in a reduced operable life of the device.
The present invention was made to overcome the above-mentioned problems. It is an object of the present invention to provide an electroluminescence device capable of maintaining stable light emissive characteristics over a prolonged service life.
In order to accomplish the object, an electroluminescence device with shock buffer function and a sealing member with shock buffer function for an electroluminescence device have the following features.
An electroluminescence device with shock buffer function comprises an emissive element substrate having a first electrode formed on a substrate and a second electrode formed above the first luminous electrode and an intervening emissive layer; a sealing member for sealing an element forming surface of the emissive element substrate; and shock buffers arranged in a gap between said emissive element substrate and said sealing member.
The shock buffers, each of which is disposed in the gap between the emissive element substrate and the sealing member, can absorb or dampen externally applied vibration and shock which otherwise would be transmitted to the sealing member. Thus, this approach suppresses the damage of the emissive element substrate and enables production of a stable EL device having a long serviceable life.
In the electroluminescence device with shock buffer function, the shock buffers may protrude from or may be securely fixed in the surface of the sealing member which faces the emissive element substrate.
A flexible shock buffer may be disposed over the entire upper surface of an emissive element substrate. However, a shock buffer formed of a hard material may be preferably disposed on non-emissive areas other than emissive areas of the emissive element substrate. The hard shock buffer can distribute the externally-applied force but it cannot completely absorb the shock. Hence, it is preferable that the shock buffer not be disposed on the luminous area. Particularly, the hard shock buffer is previously fixed on the opposite surface of the element forming substrate, which confronts the sealing member, or that it protrudes toward the side of the opposite surface, so that the hard shock buffer is disposed over areas other than luminous areas.
In a sealing member which covers an element forming surface of an emissive element substrate, the emissive element substrate having a first electrode formed on a substrate and a second electrode formed above both the first electrode and an intervening emissive layer; the sealing member may comprise shock buffers protruding from or securely fixed in the surface of the sealing member facing the emissive element substrate.
For example, the sealing member may cover the emissive element substrate which has shock buffers fixed on the back surface thereof. This structure can provide a stable EL device that has anti-vibration or shock-absorbing characteristics and, therefore, a longer operating life. A glass substrate may be used for the sealing member. Pillar-like shock buffers, each of which is made of a resist material, may be mounted on the sealing member in a manner such that they protrude toward the element forming substrate.