Patent Publication Number: US-9843015-B2

Title: Light-emitting device

Description:
This application is a continuation of copending U.S. application Ser. No. 15/165,169 filed on May 26, 2016 which is a continuation of U.S. application Ser. No. 14/255,394 filed on Apr. 17, 2014 (now U.S. Pat. No. 9,368,517 issued Jun. 14, 2016) which is a continuation of U.S. application Ser. No. 13/683,593 filed on Nov. 21, 2012 (now U.S. Pat. No. 8,716,933 issued May 6, 2014) which is a continuation of U.S. application Ser. No. 13/284,031, filed on Oct. 28, 2011 (now U.S. Pat. No. 8,319,424 issued Nov. 27, 2012) which is a continuation of U.S. application Ser. No. 12/416,356, filed on Apr. 1, 2009 (now U.S. Pat. No. 8,049,419 issued Nov. 1, 2011) which is a continuation of U.S. application Ser. No. 11/484,195, filed on Jul. 11, 2006 (now U.S. Pat. No. 7,514,864 issued Apr. 7, 2009) which is a continuation of U.S. application Ser. No. 11/083,189, filed on Mar. 17, 2005 (now U.S. Pat. No. 7,145,289 issued Dec. 5, 2006) which is a continuation of U.S. application Ser. No. 09/732,049, filed on Dec. 7, 2000 (now U.S. Pat. No. 6,894,431 issued May 17, 2005), which are all incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a device having an element (hereinafter referred to as luminous element) that is comprised of a luminous material sandwiched between electrodes (the device will hereinafter be referred to as light-emitting device), and to a method of manufacturing the same. Specifically, the present invention relates to a light-emitting device using a luminous material that provides EL (Electro Luminescence) (hereinafter referred to as EL material). 
     2. Description of the Related Art 
     In recent years, development is proceeding in a light-emitting device (EL display device) using a luminous element that utilizes the EL phenomenon of a luminous material (hereinafter referred to as EL element). The EL display device is a display device that uses a luminous element which itself has a light-emitting ability, that is, self-emissive, and hence, unlike a liquid crystal display device, does not need a back light. In addition, the EL display device has merits such as a wide field of vision, light weight, and a low power consumption. 
     Such an El display device is constructed of a structure that has an EL element composed of an anode, a cathode, and an EL material sandwiched therebetween. By applying a voltage between the anode and the cathode to make a current flow in the EL material, carriers re-couple, whereby the EL element emits light. Such a driving method is called a current drive. However, in the EL display device which has the current drive, there is a problem of a phenomenon in which a voltage drop (also referred to as an IR drop) caused by a wiring resistance occurs. This phenomenon is that the voltage becomes lower as its distance from a power source becomes farther even if it is the voltage of the same wiring. This problem is particularly conspicuous when the wiring becomes long. Thus, it is a large obstacle in making the screen of the EL display device larger. 
     When the wiring is made of a material such as tantalum, tungsten, or silicon, the EL display device is susceptible to the influence of the wiring resistance, which may become the cause of immensely reducing the homogeneity of the quality of the image. In addition, in case of using a low resistant material such as aluminum or copper, when the draw-around distance is long, then the same thing can be observed, i.e., the aforementioned phenomenon will occur. 
     The above-mentioned problem will be explained here with reference to  FIG. 2 . Shown in  FIG. 2  is a portion of a pixel portion of an active matrix EL display device. An “n” number of pixels denoted by A 1 , A 2 , . . . A n  are arranged in the up and down direction (vertical direction) of the diagram. Reference symbol  201  denotes a gate wiring,  202  denotes a source wiring, and  203  denotes a current supply line. Furthermore, a switching TFT  204 , a storage capacitor  205 , a current control TFT  206 , and an EL element  207  are formed in a region that is surrounded by the gate wiring  201 , the source wiring  202 , and the current supply line  203 . 
     At this point, the voltage of the current supply line  203  drops as the current supply line  203  moves towards the bottom of the diagram due to the influence of the voltage drop. That is, a voltage V 1  that was in the upper part of the pixel portion becomes a voltage V 2  in the lower part of the pixel portion, becoming a relationship of V 1 &gt;V 2 . This influence becomes more conspicuous as the area of the pixel portion (image display region) is made larger. 
     As a result, in case of making the EL elements of each of the pixels emit light in the same brightness, the pixel denoted by A 1  and the pixel denoted by A 2  will emit light in about the same brightness. However, the brightness of the light emitted by the pixel denoted by A n  declines compared with the pixel denoted by A 1  and the pixel denoted by A 2 . The reason for this originates in that the voltage applied to the EL element of the pixel denoted by A n  has declined due to the voltage drop. 
     Further, the influence of such voltage drop is imparted not only to the current supply line  203  but also to the gate wiring  201  and the source wiring  202 . In other words, there is a concern that the gate wiring  201  may not be able to open a gate of the switching TFT  204  because of the voltage drop. In addition, the source wiring  202  becomes incapable of applying a desired voltage to a gate of the current control TFT  206  due to the voltage drop, leading to a fear that the brightness of the EL element will change or that the EL element will not emit light. 
     Thus, the transmission of a desired voltage becomes impossible because of the voltage drop which originates in the wiring resistance. Consequently, a drawback in which there is a considerable loss in the homogeneity of the quality of the image in the pixel portion occurs. Attempts such as contriving to apply a voltage to both ends of the wiring have been made in order to improve the above problem. However, because the wiring is drawn around longer, as a result, the influence of the voltage drop cannot be ignored. 
     In case of manufacturing a monolithic type light-emitting device in which a driver circuit portion (typically including a gate driver circuit and a source driver circuit) is integrated on the same substrate, the wiring resistance of a wiring that is drawn around between the driver circuit portion and an input terminal of an electric signal becomes a problem. The wiring resistance induces a delay of the electric signal, and therefore there is a concern that the operating speed of the gate driver circuit and the source driver circuit will be reduced. 
     Thus, drawbacks such as the considerable loss of the homogeneity of the quality of the image and the extreme decline in the operating speed of the driver circuit portion due to the voltage drop which originates in the wiring resistance and the delay of a signal occur. Such a problem becomes a particularly conspicuous problem in a light-emitting device having a large screen that is several tens inches in diagonal. 
     SUMMARY OF THE INVENTION 
     The present invention has been made in view of the above, and therefore has an object to provide a light-emitting device that has a homogenized quality of image by suppressing an influence of a voltage drop which originates in the above-mentioned wiring resistance. Further, another object of the present invention is to suppress a delay of a wiring which electrically connects a driver circuit portion and an input/output terminal to thereby enhance the operating speed of the driver circuit portion. 
     The light-emitting device of the present invention is constituted of a substrate having a luminous element formed thereon (hereinafter referred to as element-formed substrate or a first substrate) and a hardened large printed wiring board (PWB: Printed Wiring Board), which are electrically connected by a conductor (anisotropic conductive film or a bump), and is characterized in that the resistance of each of the wirings (first group of wirings) formed on the element-formed substrate is reduced. 
     It is to be noted that the hardened large printed wiring board (hereinafter referred to as printed wiring board or a second substrate) indicates a printed wiring board that has a level of hardness which does not bend or curve to some amount of impact. Typically, the hardened large printed wiring board refers to a printed wiring board that is formed of a material selected from a glass cloth epoxy, glass cloth heat-resistant epoxy, ceramic, alumina, paper-based phenol, or paper-based epoxy. In addition, it is also possible to use a transmissive glass substrate, a quartz substrate, or a plastic substrate. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects and features of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings: 
         FIGS. 1A and 1B  are diagrams showing a cross-sectional structure and a top structure of a light-emitting device, respectively; 
         FIG. 2  is a diagram illustrating the change in brightness of a pixel; 
         FIGS. 3A and 3B  are diagrams showing top structures of a light-emitting device, and  FIG. 3C  is a diagram showing a cross-sectional structure thereof; 
         FIGS. 4A and 4B  are diagrams showing a top structure and a cross-sectional structure of an EL display device, respectively; 
         FIGS. 5A and 5B  are diagrams showing a top structure and a cross-sectional structure of an EL display device, respectively; 
         FIG. 6  is a diagram showing a cross-sectional structure of an EL display device; 
         FIG. 7  is a diagram showing a cross-sectional structure of an EL display device; 
         FIGS. 8A to 8F  are views showing electric equipments of the present invention; and 
         FIGS. 9A and 9B  are views showing electric equipments of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The cross-sectional view of the light-emitting device of the present invention is shown in  FIG. 1A , and the top view thereof is shown in  FIG. 1B . Note that the cross-sectional view taken along the line A-A′ of  FIG. 1B  corresponds to  FIG. 1A . 
     In  FIG. 1A , reference symbol  101  denotes a substrate having a luminous element  102  (typically an EL element or a semiconductor diode element) formed thereon. Wirings  103  and  104  for transmitting an electric signal (hereinafter referred to as element side wiring) to the luminous element  102  are formed on the substrate  101 . These components correspond to the above-mentioned element-formed substrate. It is to be noted that a glass substrate, a quartz substrate, a plastic substrate, a silicon substrate, a ceramic substrate, or a metallic substrate may be used as the substrate  101 . 
     A printed wiring board  107  is electrically connected to the substrate  101  via conductors  105   a  and  105   b  that are provided on the wirings  103  and  104  of the element-formed substrate. It is to be noted that reference symbols  106   a  and  106   b  denote sealing agents for bonding the element-formed substrate  101  and the printed wiring board  107  together. 
     Furthermore, a group of wirings (second group of wirings) are formed on the front surface, the back surface or the interior of the printed wiring board  107 . When the wirings are formed in two or more different layers, it is referred to as a multi-layered wiring (or a lamination wiring) in the present specification. On the other hand, when one layer of wiring is formed in either the front surface, the back surface, or the interior, then it is referred to as a single-layered wiring in the present specification. In the present invention, the printed wiring board  107  may have either the multi-layered wiring or the single-layered wiring. 
     At this point, an anisotropic conductive film, a conductive paste or a bump can be used as the conductors  105   a  and  105   b . As the bump, typically, a solder bump, a metal bump, a nickel bump, or a copper bump can be used. In addition, resin having metallic particles such as silver and nickel dispersed therein can be used as the conductive paste. 
     An FPC (Flexible Printed Circuit)  108  is attached to a terminal portion of the printed wiring board  107 . Further, a wiring  110  for transmitting an electric signal, which was transmitted to an anisotropic conductive film  109 , to the conductors  105   a  and  105   b  is formed to a thickness of between 1 and 20 μm (hereinafter referred to as PWB side wiring or the second group of wirings). Typically, a pattern formed of a copper foil, a gold foil, a silver foil, a nickel foil, or an aluminum foil is used as the PWB side wiring  110 . Note that though the FPC is a printed wiring board in a broad sense, it is not included in the definition of the printed wiring board in the present invention. 
     In the light-emitting device of the present invention incorporating the above-mentioned structure, an electric signal transmitted to the FPC  108  is transmitted to the conductors  105   a  and  105   b  by the PWB side wiring  110 , and then the signal can be transmitted to the luminous element  102  via the element side wirings  103  and  104 . At this point, because the PWB side wiring  110  is made of an extremely low resistant wiring, the voltage drop which originates in the wiring resistance can be immensely suppressed, thereby making it possible to transmit nearly equivalent electric signals to the element side wirings  103  and  104 . Similarly, the wiring resistance of the PWB side wiring  110  is small, and therefore, the delay of a signal is largely suppressed. Consequently, it is possible to improve the drawback of the reduction in the operating speed of the driver circuit. 
     Further, a characteristic of the present invention is that a material selected from a glass cloth epoxy, glass cloth heat-resistant epoxy, ceramic, alumina, paper-based phenol, or paper-based epoxy is used as the material of the printed wiring board  107  so that the printed wiring board  107  has an impact-resistant property. As a result, it becomes possible to protect the luminous element from external impact, whereby a highly reliable light-emitting device can be attained. 
     A case of manufacturing an EL display device by employing the present invention will be explained in Embodiment Mode of the present invention. The top views of the EL display device manufactured by employing the present invention is shown in  FIGS. 3A and 3B . 
     Note that in Embodiment Mode, the top views of the EL display device are shown in  FIGS. 3A and 3B , and the cross-sectional view thereof is shown in  FIG. 3C .  FIG. 3C  is a cross-sectional view taken along the line A&amp;A′ in the top views of  FIGS. 3A and 3B . Further, a printed wiring board is formed from a two-layered structure in Embodiment Mode, and the respective layers are shown in  FIGS. 3A and 3B . 
     In  FIG. 3A , reference symbol  300  denotes a first printed wiring board, and a wiring  301  for aiding a current supply line (hereinafter referred to as current supply auxiliary line) is formed thereon. In the present specification, the current supply line is a wiring for supplying a current, which flows to an EL element, to each EL element, and the wiring for aiding the current supply line is a wiring that is connected in parallel to the current supply line in order to reduce the apparent wiring resistance of the current supply line. The wiring for aiding the current supply line can be made of a metallic film of copper, silver, gold, aluminum or nickel, or an alloy film containing as a main component a material selected from copper, silver, gold, aluminum, or nickel. Also, the wiring for aiding the current supply line can be formed into a layered structure made of a metallic film that is made of two or more different elements selected from copper, silver, gold, aluminum and nickel. 
     Further, a dotted line denoted by reference symbol  302  is a source driver circuit, dotted lines denoted by reference symbols  303   a  and  303   b  are gate driver circuits, and a dotted line denoted by reference symbol  304  is a pixel portion. These driver circuits and the pixel portion are formed on an element-formed substrate  330  (refer to  FIG. 3C ). In addition, a thick dotted line denoted by reference symbol  305  is a current supply line that is formed on the element-formed substrate  330 . In a contact portion  306  at this point, the current supply auxiliary line  301  is electrically connected to a conductor  307 , and further electrically connected to the current supply line  305  via the conductor  307 . 
     Thus, the current supply auxiliary line  301  that is made of a low resistant material such as a copper foil is formed on the first printed wiring board  300 . The current supply auxiliary line  301  is electrically connected to the current supply line  305 , that is formed on the element-formed substrate  330 , via the contact portion  306 . Accordingly, it is possible to make the electric potential equal in any position of the current supply line  305 , and therefore, the voltage drop of the current supply line  305  can be substantially suppressed. 
     In  FIG. 3B , reference symbol  310  denotes a second printed wiring board, and a wiring  311  for aiding a gate control wiring (hereinafter referred to as gate control auxiliary line) is formed thereon. In the present specification, the gate control wiring is a wiring for transmitting a power source signal of the gate driver circuit, a clock signal, or a start signal, and the wiring for aiding the gate control wiring is a wiring that is connected in parallel to the gate control wiring in order to reduce the apparent wiring resistance of the gate control wiring. 
     Further, the thick dotted line denoted by reference symbol  312  is a gate control wiring that is formed on the element-formed substrate. At this point, the gate control auxiliary line  311  is electrically connected to a conductor  314  via a contact portion  313 , and then further electrically connected to a gate control wiring  315  via the conductor  314 . 
     Thus, the gate control auxiliary line  311  that is made of a low resistant material such as a copper foil is formed on the second printed wiring board  310 . The gate control auxiliary line  311  is electrically connected to the gate control wiring  312  that is formed on the element-formed substrate  330  via the contact portion  313 . Accordingly, it is possible to make the electric potential equal in any position of the gate control wiring  312 , and therefore, the voltage drop of the gate control wiring  312  can be substantially suppressed. 
     In Embodiment Mode of the present invention, the first printed wiring board  300  and the second printed wiring board  310  are first adhered to each other (denoted as printed wiring board  320 ), and then the adhered boards are bonded with the element-formed substrate  330  by using a sealing agent  331 . Either the first printed wiring board  300  or the second printed wiring board  310  is electrically connected to the element-formed substrate  330  through the conductor  307  or  314 . It is to be noted that there is no limit to the position of providing the conductors  307  and  314 . 
     In Embodiment Mode, the gap between the printed wiring board  320  and the element-formed substrate  330  is prescribed by the height of the anisotropic conductive film, conductive paste or bump. It is desirable that the gap is formed between 5 μm and 1 mm (preferably between 10 and 100 μm). If the gap is too narrow, then the printed wiring board  320  and the luminous element may be in contact with each other. On the other hand, if the gap is too wide, then it becomes difficult for the anisotropic conductive film, conductive paste, or bump to secure the gap. Note that a spacer or a filler used in a liquid crystal may be used to secure the gap. 
     Furthermore, an inert gas (preferably argon gas, neon gas, nitrogen gas, or helium gas) or resin may be filled in an airtight space  321  between the element-formed substrate  330  and the printed wiring board  320 . As the resin, ultraviolet cured resin, thermosetting resin, silicone resin, epoxy resin, acrylic resin, polyimide resin, phenol resin, PVC (polyvinyl chloride), PVB (polyvinyl butylal), or EVA (ethylenevinyl acetate) may be used. 
     It is effective to provide a moisture absorbent material (typically barium oxide or cesium oxide) together with the inert gas or the resin in the interior of the airtight space  321 . 
     An important point in Embodiment Mode of the present invention is that a low resistant wiring pattern provided in the printed wiring board is electrically connected to the current supply line  305  and the gate control wiring  312  which readily become the wiring resistant problem. Thus, the occurrence of the voltage drop caused by the wiring resistance of the current supply line  305  and the gate control wiring  312  can be suppressed, whereby an EL display device that may perform a homogeneous image display can be manufactured. 
     Embodiment 1 
     In Embodiment 1, an explanation will be made with reference to  FIGS. 4A and 4B  on an active matrix EL display device that is manufactured by employing the present invention.  FIG. 4A  is a top view of an element-formed substrate (denoted by reference symbol  400  in  FIG. 4B ) having an EL element formed thereon. Indicated by the dotted lines, reference symbol  401  denotes a source driver circuit,  402  denotes a gate driver circuit, and  403  denotes a pixel portion. 
     Further, reference symbol  404  denotes a printed wiring board, and a PWB side wiring  405  is formed thereon. The dotted line indicated by reference symbol  406  denotes a first sealing member, and in the inner side surrounded by the first sealing member  406 , resin (denoted by reference symbol  407  in  FIG. 4B ) is provided between the printed wiring board  404  and the element-formed substrate  400 . It is to be noted that barium oxide (denoted by reference symbol  408  in  FIG. 4B ) is used as the moisture absorbent material doped into the resin  407 . 
     Reference symbol  409  denotes a contact portion which electrically connects the PWB side wiring  405  and connecting wirings  410   a  to  410   c  that are formed on the element-formed substrate  400 . An electric signal such as a video signal or a clock signal inputted from an FPC (Flexible Printed Circuit)  411 , which serves as a connecting terminal with an external device, is transmitted to the PWB side wiring  405 , and then is transmitted to the current supply line via the contact portion  409 . 
     A cross-sectional view corresponding to the cross-section taken along the line A-A′ of  FIG. 4A  is shown in  FIG. 4B . It is to be noted that in  FIGS. 4A and 4B , the same reference symbols are used to denote the same components. As shown in  FIG. 4B , the pixel portion  403  and the source side driver circuit  401  are formed on the substrate  400 . The pixel portion  403  is formed of a plurality of pixels each including a TFT  431  for controlling the current that flows to an EL element (hereinafter referred to as current control TFT) and a pixel electrode  432  electrically connected to the drain of the current control TFT  431 . Further, the source side driver circuit  401  is formed using a CMOS circuit in which an N channel TFT  433  and a P channel TFT  434  are combined complementarily. 
     The pixel electrode  432  is formed of a transparent conducting film (a film made of a compound of indium oxide and tin oxide in Embodiment 1) and functions as an anode of the EL element. An insulating film  435  is formed on both ends of the pixel electrode  432  where a light-emitting layer  436   a  luminescing red, a light-emitting layer  436   b  luminescing green, and a light-emitting layer luminescing blue (not shown in the drawing) are further formed. A light shielding conductive film (an alloy film of lithium and aluminum in Embodiment 1) is used to form a cathode  437  of the EL element that is further formed thereon. 
     Regarding the film deposition method of the light-emitting layers  436   a  and  436   b , any known method may be used, and an organic material or an inorganic material can be used as the material for forming the light-emitting layers. The structure of the light-emitting layer do not have to only be the light-emitting layer, but may be a lamination structure in which an electron injection layer, an electron transportation layer, a hole transportation layer, and a hole injection layer are combined. 
     In case of Embodiment 1, the cathode  437  also functions as a common wiring shared by all the pixels, and is electrically connected to the connecting wirings  410   a  to  410   c . The connecting wirings  410   a  to  410   c  are electrically connected to the PWB side wiring  405  by anisotropic conductive films  440   a  to  440   c . Furthermore, because the PWB side wiring  405  is electrically connected to the FPC  411 , as a result, the connecting wirings  410   a  to  410   c  become electrically connected to the FPC  411 . 
     Note that in Embodiment 1, the first sealing member  406  is formed by using a dispenser or the like, and a spacer (not shown) is sprayed to bond the first sealing member  406  to the printed wiring board  404 . The resin  407  is then filled into a space surrounded by the element-formed substrate  400 , the printed wiring board  404 , and the first sealing member  406 . Although resin doped with barium oxide as the moisture absorbent material is used in Embodiment 1, the barium oxide can be sealed inside the resin in massive distributions. In addition, as the material of the not shown spacer, a moisture absorbent material may be used. 
     Next, after curing the resin  407  by ultraviolet irradiation or heat application, an opening portion (not shown) formed in the first sealing member  406  is closed. Then, a second sealing member  412  is disposed so as to cover a portion of the first sealing member  406 , the printed wiring board  404 , and the FPC  411 . The second sealing member  412  may be formed of the same material as the first sealing member  406 . 
     By sealing the EL element within the resin  407  using the method as described above, the EL element is completely cut off from external environment, and the invasion by substances such as moisture and oxygen from the outside which accelerate the oxidation degradation of the organic material thus can be prevented. Accordingly, an EL display device with high reliability can be manufactured. 
     Further, the occurrence of the voltage drop caused by the wiring resistance of the current supply line and the gate control wiring provided on the element-formed substrate can be suppressed by employing the present invention, whereby an EL display device that may perform a homogeneous image display can be manufactured. 
     Embodiment 2 
     In Embodiment 2, an explanation will be made with reference to  FIGS. 5A and 5B  on a passive matrix EL display device that is manufactured by employing the present invention. It is to be noted that  FIG. 5A  is a top view thereof and  FIG. 5B  is a cross-sectional view thereof taken along the line A-A′ of  FIG. 5A . 
     In  FIG. 5B , reference symbol  501  denotes an element-formed substrate made of plastic, and reference symbol  502  denotes an anode made of a compound of indium oxide and zinc oxide. In Embodiment 2, the anode  502  is formed by the evaporation method. Though not shown in  FIGS. 5A and 5B , it is to be noted that a plurality of anodes are arranged in stripe shapes in a parallel direction in a defined space. 
     An insulating film  503  is formed such that it is orthogonal to the plurality of anodes  502  arranged in stripe shapes. In addition, the insulating film  503  is also provided in the gaps of the anodes  502  in order to insulate each of the anodes  502  separately. Therefore, the insulating film  503  is patterned into matrix when observed from the top. 
     Further, a bank  504  made of resin is formed on the insulating film  503 . The bank  504  is formed in a perpendicular direction in the space such that it is orthogonal to the anodes  502 . The shape of the bank  504  is processed into an inverted triangle (inverted taper shape). Note that the structure may be a two-layered structure where the upper layer having an eaves-shape is on the lower layer. 
     Thereafter, a light-emitting layer  505  and a cathode  506  made of an aluminum alloy are formed in succession. It is preferable to successively form both the light-emitting layer  505  and the cathode  506  under a vacuum or inert atmosphere because the light-emitting layer  505  is easily affected by moisture and oxygen. The light-emitting layer  505  may be formed of any known material. However, a polymer-based organic material is preferred from the viewpoint of an easy and simple film deposition. Also, it is preferable that the cathode  506  is formed by the evaporation method. The light-emitting layer  505  and the cathode  506  are both formed in the grooves which are formed by the bank  504 . Both are arranged in stripe shapes in a perpendicular direction in the defined space. 
     Though not shown in the figures, it is effective to provide a hole transportation layer or a hole injection layer as a buffer layer between the light-emitting layer  505  and the cathode  506 . Material such as copper pthalocyanine, polythiophene, or PEDOT can be used as the hole injection layer. 
     Thus, an EL element is formed on the element-formed substrate  501  by the above described method. Note that because the bottom electrode serves as a transmissive anode in Embodiment 2, the light generated in the light-emitting layer  505  is irradiated in a direction towards the bottom surface (in the direction towards the element-formed substrate  501 ) in the defined space. 
     The anodes  502  are electrically connected to a PWB side wiring  511  that is formed on a printed wiring board  510  by anisotropic conductive films  508   a  and  508   b  which are provided inside a first sealing member  507 . In Embodiment 2, the PWB side wiring  511  is a three-layered structure made up of a wiring  511   a  provided on the front surface of the printed wiring board  510 , a wiring  511   b  provided in the interior thereof, and a wiring  511   c  provided on the back surface thereof. The materials cited in the explanation of  FIG. 1  can be used as the material to form the printed wiring board  510 . 
     At this point, as shown in  FIG. 5A , the wiring  511   a  provided on the front surface of the printed wiring board  510  and the wiring  511   b  provided in the interior thereof are formed such that they are orthogonal to each other. The wiring  511   a  provided on the front surface of the printed wiring board  510  is electrically connected to the anodes  502 , and the wiring  511   c  provided on the back surface thereof is electrically connected to the cathode  506 . Further, the wiring  511   a  provided on the front surface of the printed wiring board  510  is electrically connected to an FPC  512  to thereby transmit a signal from an external equipment. 
     In Embodiment 2, the space between the element-formed substrate  501  and the printed wiring board  510  is provided with a resin  513  and a moisture absorbent material  514  that is doped into the resin  513  to thereby protect the EL element from moisture and oxygen. Of course, the space may be filled with inert gas instead of filling the space with the resin. In addition, a second sealing member  515  is provided so as to cover the entire printed wiring board  510  to thereby suppress the deterioration of the EL element. 
     By sealing the EL element within the resin  513  using the method as described above, the EL element is completely cut off from external environment, and the invasion by substances such as moisture and oxygen from the outside which accelerate the oxidation degradation of the organic material thus can be prevented. Accordingly, an EL display device with high reliability can be manufactured. 
     Further, the occurrence of the voltage drop caused by the wiring resistance of the anodes and cathodes provided on the element-formed substrate can be suppressed by employing the present invention, whereby an EL display device that may perform a homogeneous image display can be manufactured. 
     Embodiment 3 
     Shown in Embodiment 3 is a modified example of the structure of the EL display device described in Embodiment 1. The description thereof will be made with reference to  FIG. 6 . Structures of a TFT and an EL element formed on the element-formed substrate  400  are the same as those of  FIGS. 4A and 4B . Therefore, only different components will be denoted with reference symbols and explained. 
     Upon forming a structure similar to that of Embodiment 1 up to the formation of the cathode  437 , a passivation film  601  is further formed to a thickness of 50 to 500 nm (preferably between 300 and 400 nm) to cover the cathode  437 . As the passivation film  601 , a tantalum oxide film, a silicon nitride film, a silicon oxide film, a silicon oxide nitride film, or a lamination film of a combination thereof may be used. It is preferable that the film deposition thereof is performed at a temperature of 150° C. or less by vapor-phase deposition such that the EL element will not deteriorate. 
     The sealing of the EL element is completed by the passivation film  601  in Embodiment 3. That is, the EL element is protected from external substances such as moisture and oxygen by the passivation film  601 , and hence Embodiment 3 is characterized in that the reliability of the EL display device is enhanced. Accordingly, though the structure shown in  FIGS. 4A and 4B  is one in which the EL element is sealed by the resin  407  for protection from external substances, in Embodiment 3, there is no need to particularly perform such sealing. As a result, the structure of the EL display device can be simplified. 
     At this point, anisotropic conductive films  602   a  and  602   b  are not only electrically connected to the connecting wirings  410   a  to  410   c  and a PWB side wiring  604  that is formed on a printed wiring board  603 , but also carry the role of a spacer for determining the gap between the element-formed substrate  400  and the printed wiring board  603 . Of course, a separate spacer may be provided. 
     By sealing the EL element with the passivation film  601  using the method as described above, the EL element is completely cut off from external environment, and the invasion by substances such as moisture and oxygen from the outside which accelerate the oxidation degradation of the organic material thus can be prevented. Accordingly, an EL display device with high reliability can be manufactured. 
     Further, the occurrence of the voltage drop caused by the wiring resistance of the current supply line and the gate control wiring provided on the element-formed substrate can be suppressed by employing the present invention, whereby an EL display device that may perform a homogeneous image display can be manufactured. 
     Note that the constitution of Embodiment 3 may be combined with the constitution of Embodiment 1. 
     Embodiment 4 
     Shown in Embodiment 4 is a modified example of the structure of the EL display device described in Embodiment 1. The description thereof will be made with reference to  FIG. 7 . Structures of a TFT and an EL element formed on the element-formed substrate  400  are basically the same as those of  FIGS. 4A and 4B . Therefore, only different components will be denoted with reference symbols and explained. 
     In Embodiment 4, the structure of the EL element is a reversed one from that of  FIGS. 4A and 4B . A light shielding conductive film (an aluminum alloy film in Embodiment 4) is used as a pixel electrode (cathode)  701 , and a transparent conductive film (a compound film of indium oxide and zinc oxide in Embodiment 4) is used as an anode  702 . Thus, the direction of the light emitted is a direction towards the upper part of the diagram (direction indicated by an arrow). 
     Upon completion of the EL element, a covering member  704  is bonded by a first sealing member  703 , and the inside thereof is provided with a resin  706  that is doped with a moisture absorbent material  705 . A transmissive material can be used as the covering member  704 , and a resin film, a resin substrate, a plastic substrate, a glass substrate, or a quartz substrate may be used. 
     Next, a via hole is formed from the back surface of the element-formed substrate  400  to thereby form connecting wirings  707   a  and  707   b . The connecting wirings  707   a  and  707   b  are further electrically connected to a PWB side wiring  710  that is formed on a printed wiring board  709  via bumps  708   a  and  708   b  which are made of gold, solder, or nickel. The PWB side wiring  710  is electrically connected to an FPC  711 . It is to be noted that reference symbol  712  denotes a resin for bonding the element-formed substrate  400  and the printed wiring board  709 . However, it may be a structure without the provision of the resin  712 . 
     The occurrence of the voltage drop caused by the wiring resistance of the current supply line and the gate control wiring provided on the element-formed substrate can be suppressed by employing the structure of Embodiment 4, whereby an EL display device that may perform a homogeneous image display can be manufactured. 
     Embodiment 5 
     Examples of the light-emitting device employing the EL element were explained in Embodiments 1 through 4. However, the present invention may also be employed in an EC (Electro Chromic) display device, a field emission display (FED) or a light-emitting device having a light-emitting diode that employs a semiconductor. 
     Embodiment 6 
     The light-emitting device formed by implementing the present invention has superior visibility in bright locations in comparison to a liquid crystal display device because it is a self-emissive type device, and moreover its angle of vision is wide. Accordingly, it can be used as a display portion for various electronic equipment. For example, for appreciation of TV broadcasts by large screen, it is appropriate to use a display of the present invention incorporating the light-emitting device in its casing and having a diagonal equal to 20 to 60 inches. 
     Note that all displays for exhibiting information such as a personal computer display, a TV broadcast reception display, or an advertisement display are included as the display incorporating a light-emitting device in its casing. Further, the light emitting device of the present invention can be used as a display portion of the other various electronic equipment. 
     The following can be given as examples of such electronic equipment: a video camera; a digital camera; a goggle type display (head mounted display); a car navigation system; an audio reproducing device (such as a car audio system, an audio component system); a notebook personal computer; a game equipment; a portable information terminal (such as a mobile computer, a mobile telephone, a mobile game equipment or an electronic book); and an image playback device provided with a recording medium (specifically, a device which performs playback of a recording medium and is provided with a display which can display those images, such as a digital video disk (DVD)). In particular, because portable information terminals are often viewed from a diagonal direction, the wideness of the angle of vision is regarded as very important. Thus, it is preferable that the EL display device is employed. Examples of these electronic equipment are shown in  FIGS. 8 and 9 . 
       FIG. 8A  is a display incorporating a light-emitting device in its casing, containing a casing  2001 , a support stand  2002 , and a display portion  2003 . The present invention can be used in the display portion  2003 . Since the display is a self-emissive type device without the need of a backlight, its display portion can be made thinner than a liquid crystal display device. 
       FIG. 8B  is a video camera, containing a main body  2101 , a display portion  2102 , a voice input portion  2103 , operation switches  2104 , a battery  2105 , and an image receiving portion  2106 . The light emitting device of the present invention can be used in the display portion  2102 . 
       FIG. 8C  is a portion of a head fitting type EL display (right side), containing a main body  2201 , a signal cable  2202 , a head fixing band  2203 , a display portion  2204 , an optical system  2205 , and a light emitting device  2206 . The present invention can be used in the light emitting device  2206 . 
       FIG. 8D  is an image playback device (specifically, a DVD playback device) provided with a recording medium, containing a main body  2301 , a recording medium (such as a DVD)  2302 , operation switches  2303 , a display portion (a)  2304 , and a display portion (b)  2305 . The display portion (a) is mainly used for displaying image information, and the image portion (b) is mainly used for displaying character information, and the light emitting device of the present invention can be used in these image portions (a) and (b). Note that domestic game equipment is included as the image playback device provided with a recording medium. 
       FIG. 8E  is a mobile computer, containing a main body  2401 , a camera portion  2402 , an image receiving portion  2403 , operation switches  2404 , and a display portion  2405 . The light emitting device of the present invention can be used in the display portion  2405 . 
       FIG. 8F  is a personal computer, containing a main body  2501 , a casing  2502 , a display portion  2503 , and a keyboard  2504 . The light emitting device of the present invention can be used in the display portion  2503 . 
     Note that in the future if the emission luminance becomes higher, the projection of light including outputted images can be enlarged by lenses, optical fiber, or the like. Then it will become possible to use the light emitting device in a front type or a rear type projector. 
     The emitting portion of the light emitting device consumes power, and therefore it is preferable to display information so as to have the emitting portion become as small as possible. Therefore, when using the light emitting device in a display portion which mainly displays character information, such as a portable information terminal, in particular, a portable telephone and an audio reproducing device, it is preferable to drive it by setting non-emitting portions as background and forming character information in emitting portions. 
       FIG. 9A  is a portable telephone, containing a main body  2601 , a voice output portion  2602 , a voice input portion  2603 , a display portion  2604 , operation switches  2605 , and an antenna  2606 . The light emitting device of the present invention can be used in the display portion  2604 . Note that by displaying white characters in a black background in the display portion  2604 , the power consumption of the portable telephone can be reduced. 
       FIG. 9B  is an audio reproducing device, specifically a car audio system, containing a main body  2701 , a display portion  2702 , and operation switches  2703  and  2704 . The light emitting device of the present invention can be used in the display portion  2702 . Furthermore, an audio reproducing device for a car is shown in Embodiment 6, but it may also be used for a mobile type and a domestic type of audio reproducing device. Note that by displaying white characters in a black background in the display portion  2704 , the power consumption can be reduced. This is particularly effective in a mobile type audio reproducing device. 
     The range of applications of the present invention is thus extremely wide, and it is possible to apply the present invention to electronic equipment in all fields. Furthermore, any constitution of the light emitting device shown in Embodiments 1 to 6 may be employed in the electronic equipment of this embodiment. 
     Embodiment 7 
     In the case that an electric equipment having a light-emitting device according to the present invention as a display portion is used outdoors, of course the display portion is viewed sometimes when it is dark and sometimes when it is light. Though, when it is dark, what is displayed can be sufficiently recognized even if the luminance is not so high, when it is light, what is displayed may not be recognized if the luminance is not high. 
     With regard to a light-emitting device, since the luminance varies in proportion to the current or the voltage for operating the element, if the luminance is required to be higher, the power consumption has to be increased accordingly. However, if the level of the luminance of light emission is adjusted to be so high, when it is dark, the display is much brighter than needed with the power consumption being unnecessarily large. 
     In order to provide for such a case, it is effective to provide a light-emitting device according to the present invention with a function to sense with a sensor the brightness of the environment and to adjust the luminance of light emission according to the degree of the brightness. More specifically, the luminance of light emission is made high when it is light, while the luminance of light emission is made low when it is dark. As a result, a light-emitting device which can prevent the power consumption from increasing and which does not make the user feel fatigued can be realized. 
     It is to be noted that, as such a sensor for sensing the brightness of the environment, a CMOS sensor or a CCD (charge-coupled device) can be used. Such a CMOS sensor may be conventionally integrated on a substrate where a light emitting element is formed, or a semiconductor chip may be attached to the outside. Further, a semiconductor chip having such a CCD formed thereon may be attached to a substrate where a light emitting element is formed, or a part of the electric equipment having the light-emitting device as its display portion may be structured to be provided with the CCD or the CMOS sensor. 
     A control circuit for changing the current or the voltage for operating the light emitting element in response to a signal obtained by the sensor for sensing the brightness of the environment is provided, by which the luminance of light emission of the light-emitting element can be adjusted according to the brightness of the environment. It is to be noted that such adjustment may be made either automatically or manually. 
     It is to be noted that the structure of the present embodiment can be implemented in any electric equipment described in Embodiment 6. 
     In the active matrix type or the passive type of light-emitting device, the delay of a signal and the voltage drop due to a wiring resistance are reduced to thereby enhance the operating speed of the driver circuit portion and improve the homogeneity of the quality of the image in the pixel portion.