Patent Publication Number: US-2015073212-A1

Title: Endoscope Apparatus

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     One embodiment of the present invention relates to an endoscope apparatus, particularly to an endoscope apparatus provided with a light-emitting device. 
     Note that one embodiment of the present invention is not limited to the above technical field. One embodiment of the invention disclosed in this specification and the like relates to an object, a method, and a manufacturing method. One embodiment of the present invention relates to a process, a machine, manufacture, and a composition of matter. Specifically, examples of the technical field of one embodiment of the present invention disclosed in this specification include a semiconductor device, a display device, a light-emitting device, a lighting device, a method for driving any of them, and a method for manufacturing any of them. 
     Note that the light-emitting device in this specification refers to any device including a light-emitting element and includes a light source (including a lighting device). 
     2. Description of the Related Art 
     As an implement for observing the inside of an inspection object, an endoscope apparatus has been known. The endoscope apparatus is provided with a long and narrow insertion portion that can be curved. As the observation implement, for example, a fiberscope including an optical fiber and an electronic endoscope apparatus including a charge coupled device (CCD) camera and the like are given. 
     In the endoscope apparatus, lighting for lightening the inside of the inspection object is provided at the end surface of the insertion portion. As a structure of the lighting, a method in which a light source such as a xenon lamp is provided outside and light is transmitted to the end surface of the insertion portion, a structure in which a light emitting diode (LED) element is provided at the end surface of the insertion portion, or the like is used. For example, in Patent Document 1, a structure in which a light source device supplying light to an endoscope is provided and a light guide that transmits light from the light source device to an end portion is incorporated in an insertion portion is disclosed. 
     REFERENCE 
     Patent Document 
     [Patent Document 1] PCT International Publication No. WO2011/145392 
     SUMMARY OF THE INVENTION 
     In the case where the light source such as the xenon lamp is used as the lighting for lightening the inside of the inspection object, the size of the endoscope apparatus becomes large. On the other hand, with the structure including the LED element, the structure of the endoscope apparatus can be simplified, but it is difficult to improve the color rendering property of illumination light, so that it is also difficult to observe the inside of the inspection object in detail. In addition, when such a light source is used, a light-emitting area is extremely small and light with high directivity is emitted; thus, because of a shadow formed by illuminating the inside of the inspection object, a portion that cannot be observed is generated. 
     An object of one embodiment of the present invention is to provide an endoscope apparatus with which the inside of an inspection object can be observed in detail. Another object is to simplify the structure of an endoscope apparatus. Another object is to provide an endoscope apparatus which is less likely to produce a shadow. Another object is to provide an endoscope apparatus with which a three-dimensional observation is easily performed. Another object is to provide an endoscope apparatus that can control a direction of light emitted from a light source. Another object is to provide a novel endoscope apparatus. Another object is to provide a novel light-emitting device. 
     Note that the descriptions of these objects do not disturb the existence of other objects. In one embodiment of the present invention, there is no need to achieve all the objects. Other objects will be apparent from and can be derived from the description of the specification, the drawings, the claims, and the like. 
     One embodiment of the present invention is an endoscope apparatus including a tubular insertion portion including an end portion. The end portion includes a light-emitting device and an optical device. The optical device is placed on an end surface of the end portion, and the light-emitting device is provided along a side surface of the end portion. 
     The light-emitting device is preferably a surface light-emitting device. 
     The optical device is preferably an image sensor or an optical fiber. 
     The light-emitting device is preferably provided to emit light from the side surface of the end portion to the outside thereof. At this time, in particular, the light-emitting device is preferably provided to cover part of the end surface of the end portion. 
     Alternatively, it is preferable that the light-emitting device be provided to emit light from the side surface of the end portion to the inside of the end portion, and a reflection member reflecting the light be provided inside the end portion to emit the light from the end surface. At this time, in particular, it is preferable that the light-emitting device be a dual-emission light-emitting device, and the light-emitting device be provided to emit light from the light-emitting device from the side surface of the end portion to the inside and the outside of the end portion. 
     An image obtained through the optical device preferably has a first mode to observe a moving image and a second mode to take a still image. In the first mode, light whose emission luminance is greater than or equal to 100 cd/cm 2  and less than 10000 cd/cm 2  is preferably emitted continuously or intermittently, and in the second mode, light whose emission luminance is greater than or equal to 10000 cd/cm 2  and less than or equal to 500000 cd/cm 2  is preferably emitted by being synchronized with shutter speed. 
     The light-emitting device preferably includes a light-emitting element containing a light-emitting organic compound. At this time, in particular, it is preferable that a display portion displaying an image obtained through the optical device be further included, and a pixel in the display portion include a light-emitting element containing a light-emitting organic compound. 
     According to one embodiment of the present invention, an endoscope apparatus with which the inside of an inspection object can be observed in detail can be provided. In addition, the structure of an endoscope apparatus can be simplified. Moreover, it is possible to provide an endoscope apparatus which is less likely to produce a shadow, an endoscope apparatus with which a three-dimensional observation is easily performed, or an endoscope apparatus that can control a direction of light emitted from a light source. Note that one embodiment of the present invention is not limited to the above effects. For example, depending on circumstances, one embodiment of the present invention might produce another effect or might not produce any of the above effects. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the accompanying drawings: 
         FIGS. 1A to 1C  illustrate a structural example of an endoscope apparatus of one embodiment; 
         FIG. 2  illustrates a structural example of an endoscope apparatus of one embodiment; 
         FIGS. 3A and 3B  illustrate structural examples of an endoscope apparatus of one embodiment; 
         FIGS. 4A to 4C  illustrate structural examples of an endoscope apparatus of one embodiment; 
         FIGS. 5A and 5B  illustrate structural examples of an endoscope apparatus of one embodiment; 
         FIGS. 6A and 6B  illustrate structural examples of an endoscope apparatus of one embodiment; 
         FIGS. 7A to 7C  illustrate a structural example of an endoscope apparatus of one embodiment; 
         FIGS. 8A and 8B  illustrate a structural example of an endoscope apparatus of one embodiment; 
         FIGS. 9A to 9C  illustrate a structural example of an endoscope apparatus of one embodiment; 
         FIG. 10  illustrates a structural example of an endoscope apparatus of one embodiment; 
         FIG. 11  illustrates an example of a method for controlling an endoscope apparatus of one embodiment; 
         FIGS. 12A to 12C  illustrate a structural example of a light-emitting panel of one embodiment; 
         FIGS. 13A to 13C  illustrate structural examples of a light-emitting panel of one embodiment; 
         FIGS. 14A and 14B  illustrate structural examples of a light-emitting panel of one embodiment; 
         FIGS. 15A to 15D  illustrate light-emitting elements; 
         FIGS. 16A and 16B  illustrate structural examples of a light-emitting panel of one embodiment; 
         FIG. 17  illustrates a structural example of a light-emitting panel of one embodiment; 
         FIG. 18  shows voltage-luminance characteristics of a light-emitting panel of one example; 
         FIG. 19  shows an emission spectrum of a light-emitting panel of one example; 
         FIGS. 20A and 20B  illustrate a structural example of a light-emitting panel of one embodiment; 
         FIG. 21  shows voltage-luminance characteristics of a light-emitting panel of one example; 
         FIG. 22  shows an emission spectrum of a light-emitting panel of one example; 
         FIGS. 23A and 23B  illustrate a structural example of an endoscope apparatus of one embodiment; 
         FIGS. 24A and 24B  illustrate structural examples of an endoscope apparatus of one embodiment; 
         FIGS. 25A to 25C  illustrate a structural example of an endoscope apparatus of one embodiment; and 
         FIGS. 26A and 26B  illustrate structural examples of an endoscope apparatus of one embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Embodiments will be described in detail with reference to drawings. Note that the present invention is not limited to the description below, and it is easily understood by those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present invention. Accordingly, the present invention should not be interpreted as being limited to the content of the embodiments below. 
     Note that in the structures of the invention described below, the same portions or portions having similar functions are denoted by the same reference numerals in different drawings, and description of such portions is not repeated. Further, the same hatching pattern is applied to portions having similar functions, and the portions are not especially denoted by reference numerals in some cases. 
     Note that in each drawing described in this specification, the size, the layer thickness, or the region of each component is exaggerated for clarity in some cases. Therefore, embodiments of the present invention are not limited to such a scale. 
     Embodiment 1 
     In this embodiment, an example of an endoscope apparatus of one embodiment of the present invention is described with reference to drawings. 
     Structural Example 
       FIG. 1A  illustrates an endoscope apparatus  10  exemplified in this embodiment. The endoscope apparatus  10  includes an operation portion  11  that can be gripped. The operation portion  11  is provided with an operation dial  12 , an operation button  14 , and a forceps opening  15 , and the like. In addition, the operation portion  11  is connected to a connector  13  and an insertion portion  101 . The insertion portion  101  has an end portion  110  at its end. 
     The insertion portion  101  is tubular and can be curved. At least part of the end portion  110  (e.g., an end surface  122  described later and its vicinity) of the insertion portion  101  is preferably hard. By operating the operation dial  12  provided in the operation portion  11 , a part of the insertion portion  101  is curved and the direction of the end portion  110  can be freely changed. 
     The operation button  14  provided in the operation portion  11  has a function of, for example, supplying liquid such as water and a gas such as air to a through hole provided in the end portion  110  and operating suction and the like through the through hole. The forceps opening  15  leads to the through hole provided in the end portion  110 , and by inserting a forceps or the like to the forceps opening  15 , treatment can be performed. Note that a tube (such as a catheter) may be inserted to the forceps opening  15  to perform suction, air supply, water supply, or the like. 
     The connector  13  connected to the operation portion  11  may be connected to a control device or the like which is not illustrated, and may be provided with a wiring for transmitting an image signal from the end portion  110 , a wiring for supplying power to a light-emitting device  111  provided in the end portion  110 , a hole for supplying the above liquid and air, and the like. The insertion portion  101  is provided with a hole leading to the forceps opening  15  in addition to the wirings and the hole similar to those of the connector  13 . 
     The endoscope apparatus of one embodiment of the present invention may be used for medical applications to inspect, observe, or treat an inspection object, assuming that the inspection object is a human body. Alternatively, assuming that the inspection object is equipment, machinery, or the like other than the human body, the endoscope apparatus of one embodiment of the present invention may be used for inspection applications to inspect, observe, or repair the inside of these objects. 
     For example, in the case of using an endoscope apparatus specialized in observing and inspecting, in the operation portion  11 , at least the operation dial  12  may be provided, and the operation button  14 , the forceps opening  15 , and the like are not necessarily provided. 
     Alternatively, as in an endoscope apparatus  20  illustrated in  FIG. 2 , an operation portion  21  may be provided with an operation stick  22 , an operation button  24 , a display portion  25 , and the like. The endoscope apparatus  20  does not need to have a control device and the like and thus has high portability. Note that in the endoscope apparatus  20 , the operation portion  21  may be mounted with a battery or may be connected to, for example, a cable for supplying power. 
     Structural Example of End Portion 
     Next, a structural example of the end portion  110  of the insertion portion  101  is described. 
     Structural Example 1 
       FIG. 1B  is a perspective view of the end portion  110  shown in this structural example.  FIG. 1C  is a cross-sectional schematic view taken along the line A-B in  FIG. 1B . 
     The end portion  110  includes a tubular exterior member  121 . The end surface  122  of the exterior member  121  is provided with an optical device  112 , a hole  114 , and the like. In addition, inside the exterior member  121 , a belt-shaped light-emitting device  111 , a transmission path  113  connected to the optical device  112 , and the like are provided. 
     Here, one hole  114  is provided in the end surface  122 ; however, the hole  114  is not necessarily provided as illustrated in  FIG. 3A , or two or more holes  114  may be provided as illustrated in  FIG. 3B  depending on the purpose.  FIG. 3B  shows an example in which two holes  114  with different sizes are provided. 
     Furthermore, here, the exterior member  121  has a tubular shape; however, the shape is not limited to this, and the exterior member  121  may have a columnar shape or a spindle shape whose cross-sectional shape perpendicular to the extension direction is a polygon, an ellipse, or the like. An example in which the cross-sectional shape perpendicular to the extension direction is a quadrangle is shown in  FIGS. 25A ,  25 B, and  25 C. 
     The light-emitting device  111  has a long belt shape in the extension direction of the exterior member  121  and is provided along the side surface of the exterior member  121 . As illustrated in  FIG. 1C , light  120  from the light-emitting device  111  is emitted from the inside of the exterior member  121  to the outside. 
     When the insertion portion  101  is inserted into the inspection object, the light-emitting device  111  can illuminate an inner wall of the inspection object. The light emitted to the inner wall of the inspection object is reflected by the inner wall and scattered, so that the front of the end surface  122  can be indirectly illuminated with the light. At this time, the light illuminating the front is the light reflected by the inner wall (scattered light from the inner wall) around the end portion  110  and is the light with low directivity. As a result, a shadow is less easily produced inside the inspection object as compared to the case where a point light source (such as an LED or an optical fiber) is provided on the end surface  122  to illuminate the front; thus, a region that could not be viewed because of the shadow can be viewed. In particular, in the case where the inside of the inspection object has a shape including a lot of projections and depressions and in the case where the inside of machinery in which many components such as gears are incorporated is inspected, detailed observation in the depth direction can be performed. 
     Here, the light-emitting device  111  may have a structure in which a plurality of point light sources (such as an LED) is placed in a planar shape along the side surface of the exterior member  121 . In particular, a surface light-emitting device is preferably used. When the surface light-emitting device  111  is used, the inner wall of the inspection object can be uniformly irradiated, and the directivity of the light reflected by the inner wall (scattered light from the inner wall) can be further reduced. 
     As the light-emitting device  111 , a light-emitting device including a light-emitting element containing a light-emitting organic compound (organic electroluminescence (EL) element) is preferably used. In particular, a light-emitting device including a light-emitting element which emits white light is preferably used. The organic EL element emitting white light has a higher color rendering property than the LED and the like; thus, it is possible to detect a slight difference in color inside the inspection object. Furthermore, with the organic EL element, the color rendering property on the long wavelength side can be increased as compared to the case with the LED or the like. For example, a difference in color between the normal tissue and the degenerated tissue (cancer cell) inside a living body is slight; thus, it is difficult to detect the degenerated portion, particularly at an early stage, in the case where the LED or the like is used. However, by using the light-emitting device  111  including an organic EL element with high color rendering property on the long wavelength side, the degenerated portion can be easily detected at an early stage. 
     Note that one embodiment of the present invention is not limited thereto. Another light source of the organic EL element may be additionally provided in some cases. Alternatively, the LED may be provided in addition to the organic EL element. 
     Furthermore, as the light-emitting device  111 , a flexible light-emitting panel is preferably used. For example, an extremely thin light-emitting panel in which a light-emitting element is provided over a flexible substrate is used. As described above, the light-emitting device  111  has flexibility, whereby the light-emitting device  111  can be easily deformed along an inner curved surface of the exterior member  121 . Moreover, in the case where a flexible material such as an elastic body is used as the exterior member  121 , even when the exterior member  121  is curved or the exterior member  121  is deformed by external force, the light-emitting device  111  can be deformed in accordance with the deformation of the exterior member  121 . For example, the insertion portion  101  is inserted into the inspection object and the end portion  110  is easily deformed when the end portion  110  is in contact with the inner wall of the inspection object, whereby the inner wall of the inspection object can be prevented from being damaged, for example. 
     Note that one embodiment of the present invention is not limited thereto. For example, a light-emitting panel provided over a glass substrate may be provided in addition to the flexible light-emitting panel or instead of the flexible light-emitting panel. 
     In  FIGS. 1A to 1C , four light-emitting devices  111  are provided along the extension direction of the exterior member  121 ; however, the number of the light-emitting devices  111  is not limited to this and one or more light-emitting devices  111  may be provided. In the case where the plurality of light-emitting devices  111  is provided, the light-emitting devices  111  are preferably arranged at regular intervals along the periphery of the exterior member  121  to improve the uniformity of light. Furthermore, in the case where the plurality of light-emitting devices  111  is provided, these light-emitting devices  111  may emit light with the same luminance or emission luminance may be individually controlled. For example, emission luminance of the plurality of light-emitting devices  111  is individually controlled in accordance with a positional relationship or a distance between the end portion  110  and the inner wall of the inspection object, whereby the front of the end surface  122  can have optimal brightness. 
     In the exterior member  121 , for at least a region to which light from the light-emitting device  111  is emitted, a transparent member is used. To increase the light extraction efficiency, at least one of the inside and the outside of the exterior member  121  may be provided with a light extraction member such as a microlens array or a light diffusion sheet, or a surface of the exterior member  121  may be provided with fine unevenness. 
     As the optical device  112 , for example, an image sensor such as a CCD image sensor and a complementary metal oxide semiconductor (CMOS) image sensor, a fiberscope including an optical fiber, or the like can be used. In particular, from the viewpoint of the resolution and color reproducibility, the CCD image sensor is preferably used. 
     In the case were the image sensor is used as the optical device  112 , a signal line connected to the image sensor and a wiring such as a power supply line correspond to the transmission path  113 . Alternatively, in the case where the fiberscope is used as the optical device  112 , the transmission path  113  and the optical device  112  are not distinguished, and both of them correspond to a bundle of optical fibers. 
     One embodiment of the present invention is not limited thereto, and for example, the transmission path  113  is not provided, and data may be wirelessly transmitted instead. 
     In the endoscope apparatus  10  including the insertion portion  101  including the end portion  110  shown in the structural example, the end portion  110  is provided with a light source that illuminates the inside of the inspection object, whereby it is not necessary that a relatively large light source be provided outside as in the case where the xenon lamp is used as the light source. Thus, the structure of the endoscope apparatus can be simplified. Moreover, light is emitted from the side surface of the end portion  110  of the insertion portion  101  to illuminate the inner wall of the inspection object, whereby the shadow is not easily produced, and an endoscope apparatus which can observe the inside of the inspection object in detail can be obtained. In particular, the light-emitting device  111  in which an organic EL element is used in the end portion  110  is used, whereby an endoscope that can detect a slight difference in color can be obtained. 
     The above is the description of Structural Example 1. 
     Modification Example 1 
     A structural example of the end portion  110  that is partly different from Structural Example 1 is described below. Note that description of the portions already described is omitted and different portions are described in detail. 
     In Structural Example 1, the belt-shaped light-emitting device  111  is provided along the extension direction of the exterior member  121 ; however, one embodiment of the present invention is not limited thereto, and the light-emitting device  111  can be provided as follows, for example. 
     In a structure in  FIG. 4A , the belt-shaped light-emitting device  111  is provided along the circumference direction of the side surface of the tubular exterior member  121 . In  FIG. 4A , the plurality of belt-shaped light-emitting devices  111  is provided; however, the number of the belt-shaped light-emitting devices  111  is preferably one or more. By providing the plurality of light-emitting devices  111  in parallel, a light-emitting area can be increased. By providing the plurality of belt-shaped light-emitting devices  111  which is apart from each other, stress applied to the light-emitting device  111  can be relieved even when the end portion  110  is curved, so that the light-emitting device  111  can be prevented from being damaged. 
     As describe above, the plurality of light-emitting devices  111  may be made to emit light at the same luminance, or the emission luminance of the plurality of light-emitting devices  111  may be individually controlled. 
     In a structure in  FIG. 4B , the belt-shaped light-emitting device  111  is provided in a spiral along the side surface of the tubular exterior member  121 . With such a structure, as in the structure in  FIG. 4A , stress applied to the light-emitting device  111  because of the deformation of the end portion  110  can be relieved. Moreover, one long belt-shaped light-emitting device is placed in a spiral in this manner, whereby the number of components can be reduced. 
     In  FIG. 4C , a light-emitting device  111  with a net-like shape is provided along the side surface of the exterior member  121 . The light-emitting device  111  has a net-like shape in this manner, whereby in-plane uniformity in emission of the light-emitting device  111  can be improved and the light-emitting device  111  can have elasticity in the extension direction of the end portion  110 ; thus, stress applied to the exterior member  121  at the time of deformation of the exterior member  121  can be reduced. 
     With the use of the flexible exterior member  121 , the end portion  110  may have flexibility.  FIG. 23A  is a side view of the end portion  110  in  FIG. 4A .  FIG. 23B  illustrates the end portion  110  part of which is curved. It is preferable that the state of  FIG. 23A  be freely changed into the state of  FIG. 23B . As a result, the emission direction of the light  120  can be changed. In other words, the light-emission direction of a light source can be controlled. Consequently, the light  120  can be emitted from an appropriate direction; thus, a shadow cannot be easily produced. 
     Alternatively, it is preferable that only the light-emitting device  111  be freely deformed. For example,  FIG. 26A  is a side view of the end portion  110  in  FIG. 25A . Here,  FIG. 26B  illustrates an example in which only the light-emitting device  111  is deformed. The light-emitting device  111  in a portion that is far from the end surface  122  is supported and the light-emitting device  111  in a portion near the top surface  122  is curved toward the outside of the exterior member  121  to be apart from the exterior member  121 , whereby the light-emitting device  111  is deformed so that a rear surface (a surface in contact with the exterior member  121  before the deformation) of the light-emitting device  111  can be seen from the top surface  122  side. The curvature of the portion in which the light-emitting device  111  is curved toward the outside of the exterior member  121  can be changed as needed. As a result, only the light-emitting device  111  can be deformed while the exterior member  121  and the optical device  112  in the exterior member  121  are not deformed. Thus, only the emission direction of the light  120  can be changed. Consequently, for example, when there is a projection or the like inside the inspection object, only the emission direction of the light  120  can be changed while the position of the optical device  112  is not changed; thus, unevenness, depressions and projections, and the like can be observed in more detail. In other words, a three-dimensional observation can be easily achieved. 
     In the case where the light-emitting device  111  is moved, a dual-emission light-emitting device is preferably used as the light-emitting device  111 . Alternatively, light is emitted from both sides because two light-emitting devices  111  overlap with each other, which is preferable. As a result, as illustrated in  FIG. 26B , not only the light  120 , but also a light  120 A is emitted; thus, the state of lighting can be controlled more appropriately. In the case where the light  120 A is emitted, the light  120  is not necessarily emitted. 
     An example in which the light-emitting device  111  is provided in the end portion  110 ; however, one embodiment of the present invention is not limited thereto. The light-emitting device  111  may be provided in only a position other than the end portion  110  or may be provided in both of the end portion  110  and a position other than the end portion  110 . In  FIGS. 24A and 24B , examples in which the light-emitting device  111  is provided in a region other than the end portion  110  in the insertion portion  101  are shown. The light-emitting device  111  is provided in the insertion portion  101  near the end portion  110 , whereby a shadow cannot be easily produced. Moreover, in the case where the insertion portion  101  has flexibility, the emission direction of the light  120  can be changed by the flexible light-emitting device  111 . In other words, the light-emission direction of the light source can be controlled. As a result, the light  120  can be emitted from an appropriate direction; thus, a shadow cannot be easily produced. 
     The above is the description of Modification Example. 
     Structural Example 2 
     A structural example of the end portion  110  that can also emit light to the front of the end surface of the end portion  110  as well as from the side surface of the end portion  110 . 
     In the end portion  110  in  FIG. 5A , in addition to the structure in  FIGS. 1A to 1C , the side surface  122  is provided with a light-emitting portion  116  and a transmission path  117  connected to the light-emitting portion  116 . 
     As the light-emitting portion  116 , a light-emitting element such as an LED element and an organic EL element, an optical fiber that transmits light from a light source such as a xenon lamp, or the like can be used. In particular, the organic EL element is preferably used in terms of a color rendering property of light and simplification of an apparatus. 
     In the case where the light-emitting element is used as the light-emitting portion  116 , the transmission path  117  corresponds to a wiring that transmits signals and power for driving the light-emitting element. On the other hand, in the case where the optical fiber or the like is used as the light-emitting portion  116 , the light-emitting portion  116  and the transmission path  117  are not distinguished from each other and both of them correspond to the optical fiber. 
     As described above, by providing the light-emitting device  111  that emits light from the side surface of the end portion  110  and the light-emitting portion  116  that emits light to the front of the end surface  122  at the same time, the front of the end surface  122  can be brightly irradiated with the light from the light-emitting portion  116  and the shadow portion that can be produced at this time can be irradiated with light reflected by an inner wall of an inspection object; thus, the inside of the inspection object can be observed in detail. 
     A structure of the end portion  110  in  FIG. 5B  is different from the structure in  FIG. 4A  in the shape of the end portion  110  around the end surface  122 . Specifically, the external diameter of the end surface  122  is smaller than the external diameter of the exterior member  121 , a surface shape has a gentle gradient from the end surface  122  to the side surface of the exterior member  121 , and the light-emitting device  111  is placed along the gradient portion. Thus, part of the light from the light-emitting device  111  is emitted to the front of the end surface  122 ; thus, the front of the end surface  122  can be brightly irradiated. 
     In a structure of the end portion  110  in  FIG. 6A , a belt-shaped light-emitting device  111  is provided to cover the side surface of the exterior member  121  and part of the end surface  122 . In a structure of the end portion  110  in  FIG. 6B , a cross-shaped light-emitting device  111  is provided to cover the side surface of the exterior member  121  and part of the end surface  122 . Furthermore, in the structures in  FIGS. 6A and 6B , openings are formed in the light-emitting device  111  in regions overlapping with the hole  114  and the optical device  112  provided on the end surface  122 . 
     As described above, by providing the light-emitting device  111  to cover part of the end surface  122 , light can be emitted from the side surface of the end portion  110  and to the front of the end surface  122  at the same time, and the front of the end surface  122  can be brightly irradiated and the shadow portion that can be produced at this time can be irradiated with light reflected by the inner wall of the inspection object; thus, the inside of the inspection object can be observed in detail. 
     In addition, as illustrated in  FIGS. 6A and 6B , one continuous light-emitting device  111  is provided to cover the side surface of the exterior member  121  and part of the end surface  122 , whereby the number of components can be reduced. 
     The above is the description of Structural Example 2. 
     Structural Example 3 
     A structural example of the end portion  110  whose structure is partly different from the above structure is described below. 
       FIG. 7A  is a schematic perspective view of the end portion  110  described in this structural example.  FIGS. 7B and 7C  are schematic cross-sectional views taken along the section lines C-D and E-F in  FIG. 7A , respectively. 
     The end portion  110  in  FIGS. 7A to 7C  is mainly different from the structure of the end portion in  FIGS. 1A to 1C  in the structure of the end surface  122  and the light-emitting direction of the light-emitting device  111 , and in that a reflection member  123  is provided. 
     The light-emitting device  111  is provided along the side surface of the exterior member  121  and light is emitted from the side surface of the exterior member  121  to the inside thereof. 
     The reflection member  123  provided inside the exterior member  121  reflects light at, at least, a surface facing the light-emitting device  111 . As illustrated in  FIG. 7C , the reflection member  123  is placed to be inclined to the extension direction of the end portion  110  so that the distance between the reflection member  123  and the light-emitting device  111  becomes longer as the reflection member  123  is close to the end surface  122 . Thus, the light  120  emitted from the light-emitting device  111  is reflected by the reflection member  123 , and part of the light  120  is emitted to the front of the end surface  122 . 
     It is preferable that the angle between the reflection member  123  and the light-emitting device  111  be closer to 45′; however, as the angle between the reflection member  123  and the light-emitting device  111  is smaller, a light-emitting area of the light-emitting device  111  can be increased and the luminance of the light emitted from the end surface  122  can be higher. The angle between the reflection member  123  and the light-emitting device  111  may be set as appropriate in the range of 1° to 45° in consideration of an internal diameter of the exterior member  121 , thicknesses of the light-emitting device  111 , the reflection member  123 , and the like, and a spatial limitation. 
     A region  125  between the reflection member  123  and the light-emitting device  111  is filled with a light-transmitting material. Here, when a material that has a high index of refraction is used for the region  125  between the reflection member  123  and the light-emitting device  111 , total reflection easily occurs between the light-emitting device  111  and the region  125 , and the reflection is repeated between the reflection member  123  and the light-emitting device  111 , whereby the light can be confined in the region  125 . As a result, the luminance of the light emitted from the end surface  122  can be increased. 
     On the end surface  122  in a region from which light is emitted, a concave lens  124  is provided. With the concave lens  124 , the light emitted from the end surface  122  can be diffused; thus, the front of the end surface  122  can be observed over a wider range. Alternatively, as illustrated in  FIGS. 8A and 8B , instead of the concave lens  124 , a convex lens  126  may be provided. By placing the convex lens  126  on the end surface  122 , the light emitted from the end surface  122  can converge to increase the luminance. 
     A Fresnel lens is used as the concave lens  124  and the convex lens  126 , whereby the thickness of the lens can be reduced. Alternatively, instead of the concave lens  124  or the convex lens  126 , a cylindrical lens, a toroidal lens, or a light extraction member such as a microlens array or a light diffusion sheet may be provided on the end surface  122 . By providing the lens or the light extraction member, light extraction efficiency can be improved to increase the luminance of the light emitted from the end surface. Note that such a lens and a light extraction member are not necessarily provided. 
     In the structures of the end portion  110  in  FIGS. 7A to 7C  and  FIGS. 8A and 8B , almost all the region of the end surface  122  other than the region where the optical device  112  and the hole  114  are provided can be used as a light-emitting region. In other words, surface light emission can be performed to the front of the end surface  122 . Thus, as compared to the case where the point light source (such as an LED and an optical fiber) is provided on the end surface  122  and illuminates the front, a shadow is not easily produced inside the inspection object; thus, the inside of the inspection object can be observed in detail. 
     In addition, by using a surface light-emitting device as the light-emitting device  111  provided in the exterior member  121 , the light-emitting area of the light-emitting device  111  is extremely large as compared to the case of using the point light source such as an LED. Thus, the light from the surface light-emitting device  111  converges and is emitted from the end surface  122 , whereby light with extremely high luminance can be emitted to the front of the end surface  122 . 
     Modification Example 2 
     A structural example of the end portion  110  that is partly different from Structural Example 3 is described below. 
       FIG. 9A  is a schematic perspective view of the end portion  110  described below.  FIGS. 9B and 9C  are schematic cross-sectional views taken along the section lines G-H and I-J in  FIG. 9A , respectively. 
     The end portion  110  in  FIGS. 9A to 9C  is mainly different from Structural Example 3 in that a light-emitting device  131  is provided instead of the light-emitting device  111 . The light-emitting device  131  is a dual-emission light-emitting device. 
     As illustrated in  FIGS. 9B and 9C , the light-emitting device  131  emits the light  120  from the side surface of the exterior member  121  to the inside thereof and emits the light  120  from the side surface of the exterior member  121  to the outside thereof. 
     The light  120  emitted from the side surface of the exterior member  121  to the inside thereof is reflected by the reflection member  123 , and part of the light  120  is emitted to the front of the end surface  122 . In addition, with the light  120  emitted from the side surface of the exterior member  121  to the outside thereof, the inner wall of the inspection object can be irradiated. 
     With the end portion  110  having such a structure, the front of the end portion  110  can be brightly irradiated, and at the same time, the shadow portion produced by the irradiation can be irradiated with indirect light reflected by the inner wall of the inspection object; thus, the inside of the inspection object can be observed in detail. 
     The above is the description of the structural example of the end portion. 
     In each of the structures of the end portions in Structural Example 2, Structural Example 3, and Modification Example 2, the shape of the light-emitting device provided on the side surface of the end portion can be combined with any of the shapes of the light-emitting device in Structural Example 1 and Modification Example 1. In the structural examples and the modification examples, a light-emitting element such as an LED element and an organic EL element, an optical fiber that transmits light from a light source such as a xenon lamp, or the like may be provided on the end surface as appropriate. 
     Example of Control Method 
     A structural example and an example of a control method to control the endoscope apparatus described in the above structural examples and the like are described below. 
       FIG. 10  is a block diagram showing a main part of an endoscope apparatus  50  described below. The endoscope apparatus  50  includes a display portion  51 , a control portion  52 , a memory device  53 , an operation portion  54 , and an insertion portion  101 . The insertion portion  101  includes an end portion  110  provided with a light-emitting device  111  and an optical device  112 . 
     The insertion portion  101 , the end portion  110 , the light-emitting device  111 , the optical device  112 , and the like can have the above structures as appropriate. 
     The control portion  52  is electrically connected to the light-emitting device  111  and the optical device  112  through a wiring provided in the operation portion  54  and the insertion portion  101 , and can control the driving of these devices. For example, the emission luminance, emission time, timing, and the like of the light-emitting device  111  are controlled. In addition, the control portion  52  can drive the optical device  112  in accordance with photographing conditions (e.g., shutter speed, diaphragm value, and focus) and make the optical device  112  take a moving image or a still image. An image signal taken by the optical device  112  is transmitted to the control portion  52 . The control portion  52  may control the emission luminance of the light-emitting device  111  appropriately based on an image taken by the optical device  112 . 
     The control portion  52  converts the image signal input from the optical device  112  into a signal for displaying an image on the display portion  51 , and the image can be displayed on the display portion  51 . In addition, the image is converted into data and the data can be stored in the memory device  53 . 
     Here, in the display portion  51 , the pixel preferably includes a light-emitting element containing a light-emitting organic material (an organic EL element). The display portion  51  in which the organic EL element is included in the pixel has high color reproducibility and high contrast; thus, the image taken by the optical device  112  can be displayed with high reproducibility. In particular, the display portion  51  preferably has high resolution such as MD (1920×1080), 4K2K (3840×2048 or 4096×2180), or 8K4K (7680×4320). 
     In particular, in the case where the light-emitting device  111  provided in the end portion  110  also includes an organic EL element similar to the above organic EL element, the image taken by emission from the organic EL element is displayed on the display portion  51  including the pixel provided with the above organic EL element, whereby the taken image can be displayed with faithful reproducibility. In particular, a slight difference in color that can be detected by the light-emitting device  111  including the organic EL element can be faithfully reproduced on the display portion  51 ; thus, the light-emitting device  111  can be suitably used for medical or diagnostic use. 
     Next, an example of a control operation of the light-emitting device  111  and the optical device  112  in the control portion  52  of the endoscope apparatus  50  is described with reference to  FIG. 11 .  FIG. 11  is a flow chart showing control of the light-emitting device  111  and the optical device  112  in the control portion  52 . 
     First, a photographing operation is started (Step S 0 ). 
     Next, a mode is set (Step S 1 ). Here, a first mode to observe or take a moving image or a second mode to take a still image is selected. The mode can be set by a user with, for example, a user interface as needed. 
     In Step S 2 , when the first mode is selected, the operation proceeds to Step S 3 . When the mode is not the first mode, that is, the second mode is selected, the operation proceeds to Step S 4 . 
     In Step S 3 , the control portion  52  controls the light-emitting device  111  to emit light with an emission luminance of greater than or equal to 100 cd/cm 2  and less than 10000 cd/cm 2 , preferably greater than or equal to 500 cd/cm 2  and less than 10000 cd/cm 2  continuously or to emit the light intermittently (blinking continuously) so that a flicker in an image is not observed from the light-emitting device  111 . After that, the operation proceeds to Step S 6 . Here, in the case where the light is intermittently emitted, it is preferable that the light be emitted at a frequency of 30 Hz or more, 60 Hz or more, or 120 Hz or more because a flicker in an image is not observed. 
     By Step S 4 , the second mode is defined, and the operation proceeds to Step S 5 . In Step S 5 , the control portion  52  controls the light-emitting device  111  to emit light with an emission luminance of greater than or equal to 10000 cd/cm 2  and less than or equal to 500000 cd/cm 2  by being synchronized with shutter speed of the optical device  112 . After that, the operation proceeds to Step S 6 . 
     In Step S 6 , a moving image is taken. At this time, the light with an emission luminance of greater than or equal to 100 cd/cm 2  and less than 10000 cd/cm 2 , preferably greater than or equal to 500 cd/cm 2  and less than 10000 cd/cm 2  is continuously emitted from the light-emitting device  111 , which is set in Step S 3 . Alternatively, the light is intermittently emitted. 
     In Step S 7 , a still image is taken. At this time, the light with an emission luminance of greater than or equal to 10000 cd/cm 2  and less than or equal to 500000 cd/cm 2  is emitted from the light-emitting device  111  by being synchronized with shutter speed of the optical device  112 . For example, by being synchronized with shutter speed of the optical device  112 , pulsed light of 1/10000 second or more and 10 seconds or less is emitted from the light-emitting device  111 . 
     In Step S 6  or Step S 7 , at a stage where photographing is terminated, a terminating process is performed (Step S 8 ). 
     As described above, the luminance and the emission mode of the light-emitting device  111  are preferably changed between when a moving image is taken and when a still image is taken. At the time of taking the moving image, by performing continuous emission in which emission luminance is reduced, deterioration of the light-emitting element of the light-emitting device  111  is suppressed and heat generation from the light-emitting device  111  is suppressed, so that a load of the inspection object can be lightened and observation for a long time can be easily performed. Furthermore, at the time of taking the still image, the luminance of the light-emitting device  111  is increased, whereby a still image having higher image quality can be obtained. In particular, in the case where the emission luminance is low, the resolution needs to be decreased to increase the sensitivity of the optical device  112 ; however, in the case where the luminance of emission from the light-emitting device  111  is extremely high as described above, the resolution does not need to be decreased to increase the sensitivity, and a still image with higher resolution can be obtained. 
     The above is the description of the example of the control method. 
     At least part of this embodiment can be implemented in combination with any of the embodiments described in this specification as appropriate. 
     Embodiment 2 
     In this embodiment, a structure of a light-emitting panel that can be used for the above light-emitting device will be described with reference to drawings. 
     In view of the above, a light-emitting element that is a planar light source is used for a light-emitting panel in one embodiment of the present invention. For example, with the use of an organic EL element, a thin and large-area element can be formed easily. When a planar light source, a point light source, and a line light source emit the same amount of light, the planar light source can have a smaller amount of light per unit area or a shorter emission time than the point light source and the line light source. Thus, the amount of heat generation per unit area can be reduced. In addition, the planar light source releases heat easily because of its large light-emitting area. Thus, deterioration due to local heat generation of the light-emitting panel can be suppressed. A light-emitting device that has higher reliability and less deterioration of a light-emitting panel than a light-emitting device including a light-emitting diode using an inorganic material, or the like can be provided. 
     The light-emitting panel can be thinner and lighter in the case of using an organic EL element than in the case of using a conventional xenon lamp or the like. Heat generated by light emission is diffused over a large area in the light-emitting panel and is therefore released efficiently. Thus, heat accumulation in the light-emitting panel is suppressed; and, deterioration of the light-emitting panel is suppressed. 
     The light-emitting panel can be configured to emit white light by using a properly selected light-emitting organic compound. For example, a plurality of light-emitting organic compounds that emit light of complementary colors can be used. Alternatively, light-emitting organic compounds that emit light of red, green, and blue can be used. Furthermore, different emission spectra can be selected from a variety of organic compounds. Accordingly, the light-emitting device having excellent white balance can be obtained. 
     By using a light-emitting organic compound, an emission spectrum can be broadened as compared to that of a light-emitting diode with an inorganic material. Light having a broad emission spectrum is close to natural light and suitable for photography. 
     An example of a structure of a light-emitting panel in which an organic EL element is used as a light-emitting element is described below. 
     Structural Example 1 
       FIG. 12A  is a plan view of a light-emitting panel of one embodiment of the present invention, and  FIGS. 12B and 12C  are cross-sectional schematic views taken along the lines X 1 -Y 1  and X 2 -Y 2  in  FIG. 12A , respectively. Note that some components (e.g., a partition wall  1205 ) are not illustrated in  FIG. 12A  for simplicity. 
     In the light-emitting panel illustrated in  FIGS. 12A to 12C , a light-emitting element  1250  is provided over a support substrate  1220  with an insulating film  1224  therebetween. The auxiliary wiring  1206  is provided over the insulating film  1224  and is electrically connected to the first electrode  1201 . The auxiliary wiring  1206  is partly exposed and functions as a terminal. The conductive layer  1210  is electrically connected to the second electrode  1203 , and is partly exposed and functions as a terminal. An end portion of the first electrode  1201  and an end portion of a conductive layer  1210  are covered with a partition wall  1205 . In addition, the partition wall  1205  is provided to cover the auxiliary wiring  1206  with the first electrode  1201  therebetween. The light-emitting element  1250  is sealed with the support substrate  1220 , a sealing substrate  1228 , and a sealant  1227 . An outcoupling structure  1209  is attached to the surface of the support substrate  1220 . A flexible light-emitting panel can be obtained by using flexible substrates as the support substrate  1220  and the sealing substrate  1228 . 
     The light-emitting element  1250  is an organic EL element having a bottom-emission structure; specifically, the first electrode  1201  transmitting visible light is provided over the support substrate  1220 , an EL layer  1202  is provided over the first electrode  1201 , and a second electrode  1203  reflecting visible light is provided over the EL layer  1202 . 
     For the outcoupling structure  1209 , a hemispherical lens, a micro lens array, a film provided with an uneven surface structure, a light diffusing film, or the like can be used. For example, the outcoupling structure  1209  can be formed by attaching the lens or film to the support substrate  1220  with an adhesive or the like having substantially the same refractive index as the support substrate  1220  or the lens or film. 
     As methods for forming a light-emitting element over a flexible substrate in the case of fabricating a flexible light-emitting panel, there are methods such as a first method in which the light-emitting element is directly formed over a flexible substrate, and a second method in which the light-emitting element is formed over a highly heat-resistant substrate (hereinafter referred to as a formation substrate) that is different from a flexible substrate and the light-emitting element is then separated from the formation substrate and transferred to the flexible substrate. 
     When a substrate that is resistant to heat applied in the process of forming the light-emitting element, such as a glass substrate thin enough to have flexibility, is used, the first method is preferably employed, in which case the process can be simplified. 
     When the second method is employed, an insulating film with low water permeability or the like that is formed over a formation substrate can be transferred to a flexible substrate. Thus, even when an organic resin with high water permeability and low heat resistance or the like is used as a material of the flexible substrate, a flexible light-emitting panel with high reliability can be fabricated. 
     Structural Example 2 
       FIG. 13A  is a plan view of a light-emitting panel of one embodiment of the present invention, and  FIGS. 13B and 13C  are cross-sectional schematic views taken along the line X 3 -Y 3  in  FIG. 13A . Note that some components (e.g., a partition wall  1205 ) are not illustrated in  FIG. 13A  for simplicity. 
     The light-emitting panel illustrated in  FIGS. 13A to 13C  is different from the light-emitting panel described in Structural Example 1 in that openings are provided in part of the light-emitting panel. Here, different components are described in detail, and the description of Structural Example 2 can be referred to for the common components. 
     As illustrated in  FIGS. 13B and 13C , the light-emitting panel preferably includes a sealant  1226  in the opening to prevent an electrode or an EL layer from being exposed. Specifically, an opening is formed in the light-emitting panel, and then the sealant  1226  is formed to cover at least an exposed electrode and an exposed EL layer. The sealant  1226  may be the same material as or a different material from the sealant  1227 . 
       FIG. 13B  illustrates an example of an opening formed in a region where the partition wall  1205  is not provided.  FIG. 13C  illustrates an example of an opening formed in a region where the partition wall  1205  is provided. 
     Note that an outcoupling structure may be provided on a surface of the substrate. 
     Such a light-emitting panel is manufactured, and the opening is provided at the position overlapping with the optical device  112  and the hole  114  described in Embodiment 1, which can be used in the endoscope apparatus including the end portion  110  exemplified in  FIGS. 6A and 6B  and the like. Moreover, the shape or the like of the opening is varied, whereby the light-emitting device having a net-like shape as illustrated in  FIG. 4C  can be obtained. 
     Structural Example 3 
       FIG. 14A  is a cross-sectional view of a light-emitting panel described below. The light-emitting panel illustrated in  FIG. 14A  is a top-emission light-emitting panel. 
     The light-emitting panel illustrated in  FIG. 14A  includes a flexible substrate  420 , an adhesive layer  422 , an insulating film  424 , a conductive layer  408 , an insulating film  405 , an organic EL element  450  (a first electrode  401 , an EL layer  402 , and a second electrode  403 ), a conductive layer  410 , an adhesive layer  407 , a flexible substrate  428 , and an outcoupling structure  409 . The second electrode  403 , the adhesive layer  407 , the flexible substrate  428 , and the outcoupling structure  409  transmit visible light. 
     The organic EL element  450  is provided over the flexible substrate  420  with the bonding layer  422  and the insulating film  424  provided therebetween. The organic EL element  450  is sealed by the flexible substrate  420 , the adhesive layer  407 , and the flexible substrate  428 . The organic EL element  450  includes the first electrode  401 , the EL layer  402  over the first electrode  401 , and the second electrode  403  over the EL layer  402 . It is preferable that the first electrode  401  reflect visible light. The outcoupling structure  409  is attached to the surface of the flexible substrate  428 . 
     The end portions of the first electrode  401  and the conductive layer  410  are covered with the insulating film  405 . The conductive layer  410  can be formed using the same process and material as those of the first electrode  401  and is electrically connected to the second electrode  403 . 
     The conductive layer  408  over the insulating film  405  functions as an auxiliary wiring and is electrically connected to the second electrode  403 . Note that the conductive layer  408  may be provided over the second electrode  403 . Furthermore, in a manner similar to Structural Example 1, an auxiliary wiring which is electrically connected to the first electrode  401  may be provided. 
     Structural Example 4 
       FIG. 14B  is a cross-sectional view of a light-emitting panel described as an example below. The light-emitting panel illustrated in  FIG. 14B  is a dual-emission light-emitting panel. 
     The light-emitting panel in  FIG. 14B  is different from the above Structural Example 3 in that a conductive layer  419  is provided and the outcoupling structure  409  is also provided on the flexible substrate  420 . In addition, the first electrode  401 , the insulating film  424 , the adhesive layer  422 , and the flexible substrate  420  transmit visible light. 
     The conductive layer  419  is provided over the first electrode  401 . Moreover, the conductive layer  419  can be formed in the same process and using the same materials as those of the conductive layer  410 . The conductive layer  419  serves as an auxiliary wiring and is electrically connected to the first electrode  401 . As illustrated in  FIG. 14B , the conductive layer  419  is provided to overlap with the insulating film  405 , whereby a decrease in light-emitting area can be suppressed, which is preferable. 
     [Material of Light-emitting Panel] 
     Examples of materials that can be used for the light-emitting panel of one embodiment of the present invention are described below. 
     [Substrate] 
     The substrate on the side from which light from the light-emitting element is extracted is formed using a material that transmits the light. For example, a material such as glass, quartz, ceramics, sapphire, or an organic resin can be used. 
     The weight and thickness of the light-emitting panel can be decreased by using a thin substrate. Furthermore, a flexible light-emitting panel can be obtained by using a substrate that is thin enough to have flexibility. 
     Examples of glass include alkali-free glass, barium borosilicate glass, and aluminoborosilicate glass. 
     Examples of a material that has flexibility and transmits visible light include flexible glass, polyester resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), a polyacrylonitrile resin, a polyimide resin, a poly(methyl methacrylate) resin, a polycarbonate (PC) resin, a polyethersulfone (PES) resin, a polyamide resin, a cycloolefin resin, a polystyrene resin, a polyamide imide resin, and a polyvinyl chloride resin. Specifically, a material whose thermal expansion coefficient is low is preferably used and a polyamide imide resin, a polyimide resin, and polyethylene terephthalate (PET) can be favorably used, for example. A substrate in which a glass fiber is impregnated with an organic resin or a substrate whose thermal expansion coefficient is reduced by mixing an organic resin with an inorganic filler can also be used. A substrate using such a material is lightweight, and a light-emitting panel using this substrate can also be lightweight accordingly. 
     Since the substrate through which light emission is not extracted does not need to have a light-transmitting property, a metal substrate using a metal material or an alloy material or the like can be used in addition to the above-described substrates. A metal material and an alloy material, which have high thermal conductivity, are preferably used, in which case heat can be conducted to the whole sealing substrate, so that a local temperature rise in the light-emitting panel can be prevented. To obtain flexibility and bendability, the thickness of a metal substrate is preferably greater than or equal to 10 μm and less than or equal to 200 μm, more preferably greater than or equal to 20 μm and less than or equal to 50 μm. 
     Although there is no particular limitation on a material of the metal substrate, it is preferable to use, for example, aluminum, copper, nickel, a metal alloy such as an aluminum alloy and stainless steel. 
     It is preferable to use a substrate subjected to insulation treatment in such a manner that a surface of the conductive substrate is oxidized or an insulating film is formed on the surface. An insulating film may be formed by, for example, a coating method such as a spin-coating method or a dipping method, an electrodeposition method, an evaporation method, or a sputtering method. An oxide film may be formed on the substrate surface by exposure to or heating in an oxygen atmosphere or by an anodic oxidation method or the like. 
     The flexible substrate may have a stacked structure of a layer of any of the above-mentioned materials and a hard coat layer (e.g., a silicon nitride layer) that protects a surface of the light-emitting panel from damage or the like, a layer (e.g., an aramid resin layer) that can disperse pressure, or the like. Furthermore, to suppress a decrease in the lifetime of the light-emitting element due to moisture and the like, an insulating film with low water permeability may be provided. For example, a film containing nitrogen and silicon (e.g., a silicon nitride film, a silicon oxynitride film) or a film containing nitrogen and aluminum (e.g., an aluminum nitride film) may be provided. 
     The substrate may be formed by stacking a plurality of layers. When a glass layer is used, a barrier property against water and oxygen can be improved and thus a reliable light-emitting panel can be provided. 
     A substrate in which a glass layer, an adhesive layer, and an organic resin layer are stacked from the side closer to a light-emitting element can be used. The thickness of the glass layer is greater than or equal to 20 μm and less than or equal to 200 μm, preferably greater than or equal to 25 μm and less than or equal to 100 μm. With such a thickness, the glass layer can have both a high barrier property against water and oxygen and a high flexibility. The thickness of the organic resin layer is greater than or equal to 10 μm and less than or equal to 200 μm, preferably greater than or equal to 20 μm and less than or equal to 50 μm. With such an organic resin layer provided on an outer side of the glass layer, breakage or a crack of the glass layer can be inhibited, resulting in increased mechanical strength. With the substrate that includes such a composite material of a glass material and an organic resin, a highly reliable and flexible light-emitting panel can be provided. 
     [Insulating Film] 
     An insulating film may be provided between the support substrate and the light-emitting element. As the insulating film, an inorganic insulating film such as a silicon oxide film, a silicon nitride film, a silicon oxynitride film, and a silicon nitride oxide film can be used. In order to suppress the entrance of moisture or the like into the light-emitting element, an insulating film with low water permeability such as a silicon oxide film, a silicon nitride film, or an aluminum oxide film is particularly preferable. For a similar purpose and with a similar material, an insulating film covering the light-emitting element may be provided. 
     [Partition Wall] 
     For the partition wall, an organic resin or an inorganic insulating material can be used. As the organic resin, for example, a polyimide resin, a polyamide resin, an acrylic resin, a siloxane resin, an epoxy resin, or a phenol resin can be used. As the inorganic insulating material, silicon oxide, silicon oxynitride, or the like can be used. In particular, a photosensitive resin is preferably used for easy formation of the partition wall. 
     There is no particular limitation on the method for forming the partition wall. A photolithography method, a sputtering method, an evaporation method, a droplet discharging method (e.g., an inkjet method), a printing method (e.g., a screen printing method or an offset printing method), or the like can be used. 
     [Auxiliary Wiring] 
     The auxiliary wiring is not necessarily provided; however, the auxiliary wiring is preferably provided because voltage drop due to the resistance of an electrode can be prevented. 
     For the auxiliary wiring, a single layer or a stacked layer using a material selected from copper (Cu), titanium (Ti), tantalum (Ta), tungsten (W), molybdenum (Mo), chromium (Cr), neodymium (Nd), scandium (Sc), or nickel (Ni) or an alloy material including any of these materials as its main component is used. Aluminum can also be used as a material of the auxiliary wiring; in this case, in order to prevent corrosion, it is preferable that the auxiliary wiring have a stacked-layer structure and aluminum be used for a layer that is not in contact with ITO or the like. The thickness of the auxiliary wiring can be greater than or equal to 0.1 μm and less than or equal to 3 μm, preferably greater than or equal to 0.1 μm and less than or equal to 0.5 μM 
     [Sealant] 
     A method for sealing the light-emitting panel is not limited, and either solid sealing or hollow sealing can be employed. For example, a glass material such as a glass frit, or a resin material such as a resin that is curable at room temperature (e.g., a two-component-mixture-type resin), a light curable resin, or a heat-curable resin can be used. The light-emitting panel may be filled with an inert gas such as nitrogen or argon, or resin such as a polyvinyl chloride (PVC) resin, an acrylic resin, a polyimide resin, an epoxy resin, a silicone resin, a polyvinyl butyral (PVB) resin, or an ethylene vinyl acetate (EVA) resin. A drying agent may be contained in the resin. 
     The above is the description of the material of the light-emitting panel. 
     At least part of this embodiment can be implemented in combination with any of the embodiments described in this specification as appropriate. 
     Embodiment 3 
     In this embodiment, light-emitting elements that can be used in the light-emitting device of one embodiment of the present invention are described with reference to  FIGS. 15A to 15D . 
     Structural Example of Light-Emitting Element 
     A light-emitting element illustrated in  FIG. 15A  includes an EL layer  203  between a first electrode  201  and a second electrode  205 . In this embodiment, the first electrode  201  serves as the anode, and the second electrode  205  serves as the cathode. 
     When a voltage higher than the threshold voltage of the light-emitting element is applied between the first electrode  201  and the second electrode  205 , holes are injected to the EL layer  203  from the first electrode  201  side and electrons are injected to the EL layer  203  from the second electrode  205  side. The injected electrons and holes are recombined in the EL layer  203  and a light-emitting material contained in the EL layer  203  emits light. 
     The EL layer  203  includes at least a light-emitting layer  303  containing a light-emitting substance. 
     In addition to the light-emitting layer, the EL layer  203  may further include one or more layers containing any of a substance with a high hole-injection property, a substance with a high hole-transport property, a substance with a high electron-transport property, a substance with a high electron-injection property, a substance with a bipolar property (a substance with a high electron-transport property and a high hole-transport property), and the like. For the EL layer  203 , either a low molecular compound or a high molecular compound can be used, and an inorganic compound may also be used. 
     A light-emitting element illustrated in  FIG. 15B  includes the EL layer  203  between the first electrode  201  and the second electrode  205 , and in the EL layer  203 , a hole-injection layer  301 , a hole-transport layer  302 , the light-emitting layer  303 , an electron-transport layer  304 , and an electron-injection layer  305  are stacked in this order from the first electrode  201  side. 
     As in light-emitting elements illustrated in  FIGS. 15C and 15D , a plurality of EL layers may be stacked between the first electrode  201  and the second electrode  205 . In that case, an intermediate layer  207  is preferably provided between the stacked EL layers. The intermediate layer  207  includes at least a charge-generation region. 
     For example, the light-emitting element illustrated in  FIG. 15C  includes the intermediate layer  207  between a first EL layer  203   a  and a second EL layer  203   b . The light-emitting element illustrated in  FIG. 15D  includes n EL layers (n is a natural number of 2 or more), and the intermediate layers  207  between the EL layers. 
     The behaviors of electrons and holes in the intermediate layer  207  provided between the EL layer  203 ( m ) and the EL layer  203 ( m+ 1) are described below. When a voltage higher than the threshold voltage of the light-emitting element is applied between the first electrode  201  and the second electrode  205 , holes and electrons are generated in the intermediate layer  207 , and the holes move into the EL layer  203 ( m +1) provided on the second electrode  205  side and the electrons move into the EL layer  203 ( m ) provided on the first electrode  201  side. The holes injected into the EL layer  203 ( m +1) are recombined with the electrons injected from the second electrode  205  side, so that a light-emitting material contained in the EL layer  203 ( m +1) emits light. The electrons injected into the EL layer  203 ( m ) are recombined with the holes injected from the first electrode  201  side, so that a light-emitting material contained in the EL layer  203 ( m ) emits light. Thus, the holes and electrons generated in the intermediate layer  207  cause light emission in the respective EL layers. 
     Note that the EL layers can be provided in contact with each other with no intermediate layer therebetween when these EL layers allow the same structure as the intermediate layer to be formed therebetween. For example, when the charge-generation region is formed over one surface of an EL layer, another EL layer can be provided in contact with the surface. 
     When the EL layers have different emission colors, a desired emission color can be obtained from the whole light-emitting element. For example, in the light-emitting element having two EL layers, when an emission color of the first EL layer and an emission color of the second EL layer are made to be complementary colors, a light-emitting element emitting white light as a whole light-emitting element can also be obtained. This can be applied to a light-emitting element including three or more EL layers. 
     [Material of Light-Emitting Element] 
     Examples of materials that can be used for each layer are given below. Note that each layer is not limited to a single layer and may be a stack of two or more layers. 
     [Anode] 
     The electrode serving as the anode (the first electrode  201 ) can be formed using one or more kinds of conductive metals, alloys, conductive compounds, and the like. In particular, it is preferable to use a material with a high work function (4.0 eV or more). Examples include indium tin oxide (ITO), indium tin oxide containing silicon or silicon oxide, indium zinc oxide, indium oxide containing tungsten oxide and zinc oxide, graphene, gold, platinum, nickel, tungsten, chromium, molybdenum, iron, cobalt, copper, palladium, and a nitride of a metal material (e.g., titanium nitride). 
     When the anode is in contact with the charge-generation region, any of a variety of conductive materials can be used regardless of their work functions; for example, aluminum, silver, and an alloy containing aluminum can be used. 
     [Cathode] 
     The electrode serving as the cathode (the second electrode  205 ) can be formed using one or more kinds of conductive metals, alloys, conductive compounds, and the like. In particular, it is preferable to use a material with a low work function (3.8 eV or less). Examples include aluminum, silver, an element belonging to Group 1 or 2 of the periodic table (e.g., an alkali metal such as lithium and cesium, an alkaline earth metal such as calcium and strontium, and magnesium), an alloy containing any of these elements (e.g., Mg—Ag or Al—Li), a rare earth metal such as europium or ytterbium, and an alloy containing any of these rare earth metals. 
     Note that when the cathode is in contact with the charge-generation region, a variety of conductive materials can be used regardless of its work function. For example, ITO, indium tin oxide containing silicon or silicon oxide, or the like can be used. 
     The electrodes may be formed separately by a vacuum evaporation method or a sputtering method. Alternatively, when a silver paste or the like is used, a coating method or an inkjet method may be used. 
     [Hole-Injection Layer  301 ] 
     The hole-injection layer  301  contains a substance with a high hole-injection property. 
     Examples of the substance with a high hole-injection property include metal oxides such as molybdenum oxide, vanadium oxide, ruthenium oxide, tungsten oxide, and manganese oxide; and phthalocyanine-based compounds such as phthalocyanine (abbreviation: H 2 Pc) and copper(II) phthalocyanine (abbreviation: CuPc). 
     Other examples of the substance with a high hole-injection property include high molecular compounds such as poly(N-vinylcarbazole) (abbreviation: PVK), poly(4-vinyltriphenylamine) (abbreviation: PVTPA); and high molecular compounds to which acid is added such as poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonic acid) (PEDOT/PSS). 
     The hole-injection layer  301  may serve as the charge-generation region. When the hole-injection layer  301  in contact with the anode serves as the charge-generation region, a variety of conductive materials can be used for the anode regardless of their work functions. Materials contained in the charge-generation region are described below. 
     [Hole-Transport Layer  302 ] 
     The hole-transport layer  302  contains a substance with a high hole-transport property. 
     The substance with a high hole-transport property is preferably a substance with a property of transporting more holes than electrons, and is especially preferably a substance with a hole mobility of 10 −6  cm 2 /Vs or more. A variety of compounds can be used. For example, an aromatic amine compound such as 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB or α-NPD) or 4-phenyl-4′-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: BPAFLP); a carbazole derivative such as 4,4′-di(N-carbazolyl)biphenyl (abbreviation: CBP), 9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviation: CzPA), or 9-phenyl-3-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviation: PCzPA); an aromatic hydrocarbon compound such as 2-tert-butyl-9,10-di(2-naphthyl)anthracene (abbreviation: t-BuDNA), 9,10-di(2-naphthyl)anthracene (abbreviation: DNA), or 9,10-diphenylanthracene (abbreviation: DPAnth); a high molecular compound such as PVK or PVTPA. 
     [Light-Emitting Layer  303 ] 
     For the light-emitting layer  303 , a fluorescent compound that exhibits fluorescence or a phosphorescent compound that exhibits phosphorescence can be used. 
     Examples of the fluorescent compound that can be used for the light-emitting layer  303  include N,N-bis[4-(9H-carbazol-9-yl)phenyl]-N,N-diphenylstilbene-4,4′-diamine (abbreviation: YGA2S), N-(9,10-diphenyl-2-anthryl)-N, 9-diphenyl-9H-carbazol-3-amine (abbreviation: 2PCAPA), and rubrene. 
     Examples of the phosphorescent compound that can be used for the light-emitting layer  303  include organometallic complexes such as bis[2-(4′,6′-difluorophenyl)pyridinato-N,C 2′ ]iridium(III) picolinate (abbreviation: FIrpic), tris(2-phenylpyridinato-N,C 2′ )iridium(III) (abbreviation: Ir(ppy) 3 ), and (acetylacetonato)bis(3,5-dimethyl-2-phenylpyrazinato)iridium(III) (abbreviation: Ir(mppr-Me) 2 (acac)). 
     The light-emitting layer  303  may have a structure in which any of the above-described light-emitting organic compounds (a light-emitting substance or a guest material) is dispersed in another substance (a host material). As the host material, a variety of kinds of materials can be used, and it is preferable to use a substance that has a lowest unoccupied molecular orbital level (LUMO level) higher than that of the guest material and has a highest occupied molecular orbital level (HOMO level) lower than that of the guest material. 
     With the structure in which the guest material is dispersed in the host material, crystallization of the light-emitting layer  303  can be suppressed. In addition, concentration quenching due to high concentration of the guest material can be suppressed. 
     As the host material, the above-described substance with a high hole-transport property (e.g., an aromatic amine compound or a carbazole derivative) or a later-described substance with a high electron-transport property (e.g., a metal complex having a quinoline skeleton or a benzoquinoline skeleton or a metal complex having an oxazole-based or thiazole-based ligand) can be used. As the host material, specifically, a metal complex such as tris(8-quinolinolato)aluminum(III) (abbreviation: Alq) or bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum(III) (abbreviation: BAIq); a heterocyclic compound such as 3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole (abbreviation: TAZ), bathophenanthroline (abbreviation: BPhen), or bathocuproine (abbreviation: BCP); a condensed aromatic compound such as CzPA, DNA, t-BuDNA, and DPAnth; or an aromatic amine compound such as NPB can be used. 
     Alternatively, as the host material, a plurality of kinds of materials can be used. For example, in order to suppress crystallization, a substance such as rubrene that suppresses crystallization may be further added. In addition, NPB, Alq, or the like may be further added in order to transfer energy to the guest material more efficiently. 
     When a plurality of light-emitting layers are provided and emission colors of the layers are made different, light emission of a desired color can be obtained from the light-emitting element as a whole. For example, in a light-emitting element having two light-emitting layers, the emission colors of first and second light-emitting layers are complementary, so that the light-emitting element can emit white light as a whole. This can be applied to a light-emitting element including three or more light-emitting layers. 
     [Electron-Transport Layer  304 ] 
     The electron-transport layer  304  contains a substance with a high electron-transport property. 
     The substance with a high electron-transport property is preferably an organic compound having a property of transporting more electrons than holes, and is especially preferably a material with an electron mobility of 10 −6  cm 2 /Vs or more. 
     As the substance with a high electron-transport property, for example, a metal complex having a quinoline skeleton or a benzoquinoline skeleton, such as Alq or Balq, can be used. Alternatively, a metal complex having an oxazole-based ligand or a thiazole-based ligand, such as bis[2-(2-hydroxyphenyl)benzoxazolato]zinc (abbreviation: Zn(BOX) 2 ) and bis[2-(2-hydroxyphenyl)benzothiazolato]zinc (abbreviation: Zn(BTZ) 2 ) can be used. Alternatively, TAZ, BPhen, BCP, or the like can be used. 
     [Electron-Injection Layer  305 ] 
     The electron-injection layer  305  contains a substance with a high electron-injection property. 
     Examples of the substance with a high electron-injection property include alkali metals, alkaline earth metals, and compounds thereof, such as lithium, cesium, calcium, lithium fluoride, cesium fluoride, calcium fluoride, and lithium oxide. A rare earth metal compound such as erbium fluoride can also be used. Any of the above substances for the electron-transport layer  304  can also be used. 
     [Charge-Generation Region] 
     The charge-generation region may have either a structure in which an electron acceptor (acceptor) is added to an organic compound with a high hole-transport property or a structure in which an electron donor (donor) is added to an organic compound with a high electron-transport property. Alternatively, these structures may be stacked. 
     Examples of the organic compound with a high hole-transport property include the above materials that can be used for the hole-transport layer, and examples of the organic compound with a high electron-transport property include the above materials that can be used for the electron-transport layer. 
     As examples of the electron acceptor, 7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviation: F4-TCNQ), chloranil, and the like can be given. In addition, transition metal oxides can be given. Moreover, oxides of metals belonging to Groups 4 to 8 of the periodic table can be given. Specifically, it is preferable to use vanadium oxide, niobium oxide, tantalum oxide, chromium oxide, molybdenum oxide, tungsten oxide, manganese oxide, and rhenium oxide because of their high electron accepting properties. Among these, molybdenum oxide is especially preferable since it is stable in the air, has a low hygroscopic property, and is easy to handle. 
     As the electron donor, it is possible to use an alkali metal, an alkaline earth metal, a rare earth metal, a metal belonging to Group 13 of the periodic table, or an oxide or a carbonate thereof. Specifically, lithium, cesium, magnesium, calcium, ytterbium, indium, lithium oxide, cesium carbonate, or the like is preferably used. Alternatively, an organic compound such as tetrathianaphthacene may be used as the electron donor. 
     The above-described layers included in the EL layer  203  and the intermediate layer  207  can be formed by any of the following methods: an evaporation method (including a vacuum evaporation method), a transfer method, a printing method, an inkjet method, a coating method, and the like. 
     The above is the description of the material of the light-emitting element. 
     At least part of this embodiment can be implemented in combination with any of the embodiments described in this specification as appropriate. 
     Example 1 
     In this example, a light-emitting panel of one embodiment of the present invention was fabricated. 
       FIG. 16A  is a plan view of a light-emitting panel fabricated in this example, and  FIG. 17  is a cross-sectional view taken along the dashed-dotted line X 1 -Y 1  in  FIG. 16A . Note that some components of the light-emitting panel are omitted in  FIG. 16A . 
     In the light-emitting panel of this example, as illustrated in  FIG. 17 , the light-emitting element  1250  is provided over the support substrate  1229  having an outcoupling structure with the insulating film  1224  therebetween. The auxiliary wiring  1206  is provided over the insulating film  1224  and is electrically connected to the first electrode  1201 . The auxiliary wiring  1206  is partly exposed and functions as a terminal. The conductive layer  1210  is electrically connected to the second electrode  1203 . An end portion of the first electrode  1201  and an end portion of a conductive layer  1210  are covered with a partition wall  1205 . In addition, the partition wall  1205  is provided to cover the auxiliary wiring  1206  with the first electrode  1201  therebetween. The light-emitting element  1250  is sealed with the support substrate  1229 , the sealing substrate  1228 , and the sealant  1227 . 
     In the light-emitting panel of this example, a diffusion film of a polyester-based resin was used as the support substrate  1229 , and a substrate including a thin glass layer and a polyethylene terephthalate (PET) layer was used as the sealing substrate  1228 . These substrates are flexible, and the light-emitting panel of this example is a flexible light-emitting panel. The area of a light-emitting region of the light-emitting panel of this example is 56 mm×42 mm. 
     The light-emitting element  1250  is an organic EL element having a bottom-emission structure; specifically, the first electrode  1201  that transmits visible light is provided over the support substrate  1229 , the EL layer  1202  is provided over the first electrode  1201 , and the second electrode  1203  that reflects visible light is provided over the EL layer  1202 . 
     A method for fabricating the light-emitting panel of this example is described. 
     First, a base film, a separation layer (a tungsten film), and a layer to be separated were formed in this order over a glass substrate that was a formation substrate. In this example, the layer to be separated includes the insulating film  1224 , the auxiliary wiring  1206 , the first electrode  1201 , and the partition wall  1205 . 
     A total of seven auxiliary wirings  1206  were formed over the insulating film  1224 . At this time, the auxiliary wirings  1206  with a width L2 of 322 μm were formed at a pitch of 5.3 mm. As the first electrode  1201 , a film of indium tin oxide containing silicon oxide (ITSO) was formed. A total of seven partition walls  1205  covering the auxiliary wirings  1206  were formed to have a width L1 of 330 μm. 
     Then, a temporary support substrate and the first electrode  1201  were attached to each other with an adhesive for separation. Then, the layer to be separated was separated from the formation substrate along the separation layer. Thus, the separated layer was provided on the temporary support substrate side. 
     Next, the layer that was separated from the formation substrate and where the insulating film  1224  was exposed was attached to the support substrate  1229  using a UV curable adhesive. As the support substrate  1229 , a diffusion film of a polyester-based resin was used as described above. Then, the temporary support substrate was separated, whereby the first electrode  1201  was exposed over the support substrate  1229 . 
     Next, the EL layer  1202  and the second electrode  1203  were formed over the first electrode  1201 . As the EL layer  1202 , a first EL layer including a light-emitting layer containing a fluorescent compound emitting blue light, an intermediate layer, and a second EL layer including a light-emitting layer containing a phosphorescent compound emitting green light and a light-emitting layer containing a phosphorescent compound emitting red light were stacked in this order from the first electrode  1201  side. Silver was used for the second electrode  1203 . 
     Then, a photo-curable resin containing zeolite that serves as the sealant  1227  was applied and cured by UV light irradiation. Next, the support substrate  1229  and the substrate including the thin glass layer and the polyethylene terephthalate (PET) layer that was the sealing substrate  1228  were attached to each other with a UV curable adhesive. 
     Operation characteristics of the light-emitting panel obtained in the above-described manner were measured. Voltage-luminance characteristics of the light-emitting panel are shown in  FIG. 18  as indicated by “initial” in a legend. An emission spectrum of the light-emitting panel is shown in  FIG. 19 . It is found from  FIG. 19  that the light-emitting panel of this example shows an emission spectrum including light originating from the fluorescent compound emitting blue light, light originating from the phosphorescent compound emitting green light, and light originating from the phosphorescent compound emitting red light. 
     After that, a light-emitting device including the light-emitting panel was subjected to a reliability test. In the reliability test, the light-emitting panel was made to emit light 3000 times or 10000 times with intervals. For each time of light emission, a current of 2 A was passed through the light-emitting panel for 50 milliseconds (ms). The current density of the light-emitting element at this time was 90 mAkm 2 . The interval between light emissions (i.e., non-light-emitting period) was 10 seconds. 
       FIG. 18  shows voltage-luminance characteristics of the light-emitting panel after 3000 times of light emission and those after 10000 times of light emission. 
     It can be seen from  FIG. 18  that the voltage-luminance characteristics of the light-emitting panel even after 10000 times of light emission does not significantly differ from those before the reliability test and that the light-emitting panel does not deteriorate. This supports that the light-emitting panel of this example has high reliability. 
     Example 2 
     In this measurement, the amount of current that can be fed to an organic EL element emitting white light was measured. The area of a light-emitting region in the organic EL element that was used was 2 mm×2 mm. For each time of light emission, current was fed to the organic EL element for 50 milliseconds (ms). 
     The examination showed that a current of 60 mA was able to be fed to the organic EL element (i.e., the current density was 1500 mA/cm 2 ). However, when a current of 68 mA was fed to the organic EL element (i.e., the current density was 1700 mA/cm 2 ), the organic EL element was short-circuited. 
     The above-described results indicate that in a light-emitting device of one embodiment of the present invention that includes the organic EL element, the amount of light can be adjusted when the current density is lower than 1700 mA/cm 2 . Thus, a larger amount of current can be fed to the organic EL element than to a light-emitting diode or the like using an inorganic material. 
     Example 3 
     In this example, a light-emitting device of one embodiment of the present invention was fabricated. 
       FIG. 16B  is a plan view of a light-emitting panel fabricated in this example,  FIG. 20A  is a cross-sectional view taken along the dashed-dotted line X 2 -Y 2  in  FIG. 16B , and  FIG. 20B  is a cross-sectional view taken along the dashed-dotted line X 3 -Y 3  in  FIG. 16B . Note that some components of the light-emitting panel are omitted in  FIG. 16B . 
     In the light-emitting panel of this example, the light-emitting element  1250  is formed over the support substrate  1220  with the insulating film  1224  therebetween. The auxiliary wiring  1206  is provided over the insulating film  1224  and is electrically connected to the first electrode  1201 . The auxiliary wiring  1206  is partly exposed and functions as a terminal. An end portion of the first electrode  1201  and an end portion of the conductive layer  1210  are covered with the partition wall  1205 . In addition, the partition wall  1205  is provided to cover the auxiliary wiring  1206  with the first electrode  1201  therebetween. The light-emitting element  1250  is sealed with the support substrate  1220 , the sealing substrate  1228 , and the sealant  1227 . 
     In the light-emitting panel of this example, a diffusion film of a polyester-based resin was used as the support substrate  1220 , and a substrate including a thin glass layer and a polyethylene terephthalate (PET) layer was used as the sealing substrate  1228 . These substrates are flexible, and the light-emitting panel of this example is a flexible light-emitting panel. Note that it can be said that the support substrate  1220  of this example has an outcoupling structure. 
     A light-emitting region in the light-emitting panel of this example is obtained by excluding a circular non-light-emitting region with a diameter of 20 mm from an area of 50 mm×52.9 mm. The non-light-emitting region includes an opening of the light-emitting panel. The non-light-emitting region does not include the auxiliary wiring  1206  and the first electrode  1201  (see  FIG. 20A ). This structure can prevent the first electrode  1201  of the light-emitting element  1250  or the auxiliary wiring  1206  from being in contact with the second electrode  1203  and being short-circuited when an opening is formed. 
     The light-emitting element  1250  is an organic EL element having a bottom-emission structure; specifically, the first electrode  1201  transmitting visible light is provided over the support substrate  1220 , an EL layer  1202  is provided over the first electrode  1201 , and a second electrode  1203  reflecting visible light is provided over the EL layer  1202 . 
     A method for fabricating the light-emitting panel of this example is described. 
     First, a base film, a separation layer (a tungsten film), and a layer to be separated were formed in this order over a glass substrate that was a formation substrate. In this example, the layer to be separated includes the insulating film  1224 , the auxiliary wiring  1206 , the first electrode  1201 , and the partition wall  1205 . 
     A total of 125 auxiliary wirings  1206  were formed over the insulating film  1224 . At this time, the auxiliary wirings  1206  with a width L2 of 3 μm were formed at a pitch of 420 μm. As the first electrode  1201 , a film of indium tin oxide containing silicon oxide (ITSO) was formed. A total of 125 partition walls  1205  covering the auxiliary wirings  1206  were formed to have a width L1 of 6 μm. The auxiliary wirings in the light-emitting panel of this example have a width as narrow as 3 μm, and thus are less likely to be recognized when the light-emitting panel emits light. 
     Then, a temporary support substrate and the first electrode  1201  were attached to each other with an adhesive for separation. Then, the layer to be separated was separated from the formation substrate along the separation layer. Thus, the layer to be separated is provided on the temporary support substrate side. 
     Next, the layer that was separated from the formation substrate and where the insulating film  1224  was exposed was attached to the support substrate  1220  with a UV curable adhesive. As the support substrate  1220 , a diffusion film of a polyester-based resin was used as described above. Then, the temporary support substrate was separated, whereby the first electrode  1201  was exposed over the support substrate  1229 . 
     Next, the EL layer  1202  and the second electrode  1203  were formed over the first electrode  1201 . As the EL layer  1202 , a first EL layer including a light-emitting layer containing a fluorescent compound emitting blue light, an intermediate layer, and a second EL layer including a light-emitting layer containing a phosphorescent compound emitting green light and a light-emitting layer containing a phosphorescent compound emitting orange light were stacked in this order from the first electrode  1201  side. Silver was used for the second electrode  1203 . 
     Then, a UV curable resin containing zeolite that served as the sealant  1227  was applied and cured by UV light irradiation. Next, the support substrate  1220  and the substrate including the thin glass layer and the polyethylene terephthalate (PET) layer that was the sealing substrate  1228  were attached to each other with a UV curable adhesive. 
     Then, a circular opening was formed to overlap a non-light-emitting region surrounded by the light-emitting region. In this example, the opening is fainted in part of the light-emitting panel with laser light having a wavelength in the UV region (i.e., UV laser light). The opening can be formed with a punch or the like instead of laser light, in which case peeling of a film, especially the EL layer  1202  or the like, might occur because of pressure applied to the light-emitting panel. Laser light is preferably used to form the opening, in which case peeling of a film can be prevented and a highly reliable light-emitting panel can be fabricated. 
     Then, an end portion of the light-emitting panel that was exposed in the opening was covered with a UV curable adhesive, and the sealant  1226  was provided. 
     Operation characteristics of the light-emitting panel obtained in the above-described manner were measured. Voltage-luminance characteristics of the light-emitting panel are shown in  FIG. 21  as indicated by “initial” in a legend. An emission spectrum of the light-emitting panel is shown in  FIG. 22 . It is found from  FIG. 22  that the light-emitting panel of this example shows an emission spectrum including light originating from the fluorescent compound emitting blue light, light originating from the phosphorescent compound emitting green light, and light originating from the phosphorescent compound emitting orange light. 
     Note that the light-emitting panel emits light at a luminance of approximately 100000 cd/m 2  when supplied with a current of 2 A. 
     After that, a light-emitting device including the light-emitting panel was subjected to a reliability test. In the reliability test, the light-emitting panel was made to emit light 50000 times with intervals. For each time of light emission, a current of 2 A was fed to the light-emitting panel for 50 milliseconds (ms). The current density of the light-emitting element at this time was 87 mA/cm 2 . The interval between light emissions (non-light-emitting period) was 0.5 seconds (s). 
       FIG. 21  shows voltage-luminance characteristics of the light-emitting panel after 50000 times of light emission. 
     It can be seen from  FIG. 21  that the voltage-luminance characteristics of the light-emitting panel even after 50000 times of light emission does not significantly differ from those before the reliability test and that the light-emitting panel does not deteriorate. It is indicated that even when the light-emitting panel is made to blink for 50 milliseconds 50000 times at intervals of 0.5 seconds, heat generation due to light emission has little influence on the light-emitting panel because the actual lighting time of the light-emitting panel is only approximately 40 minutes. 
     At least part of this example can be implemented in combination with any of the embodiments described in this specification as appropriate. 
     This application is based on Japanese Patent Application serial no. 2013-188612 filed with Japan Patent Office on Sep. 11, 2013, the entire contents of which are hereby incorporated by reference.