Abstract:
The present invention supplied a display apparatus using plastic substrate instead of glass substrate, which can solve such problems that the plastic substrate has a low heat conductivity and its heat release performance becomes bad so that it is difficult to obtain stable performance and reliability. In the display apparatus being formed by bonding semiconductor thin film element on a plastic substrate, a thin film metal layer is formed on surface of the semiconductor thin film element for promoting heat release.

Description:
This is a Divisional of U.S. application Ser. No. 12/071,943, filed on Feb. 28, 2008, and allowed on May 15, 2012, the subject matter of which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a display apparatus formed by bonding semiconductor thin film element on a plastic substrate. 
     2. Related Background Art 
     In recent years, display apparatuses are unceasingly making progress on development for lightening and thinning, and the demand for flexible display apparatuses represented by electronic paper is increasing continuously. In the past, a thin type display apparatus mainly adopted a rigid glass substrate, however, the glass substrate is weak with respect to impact, so that it easily incurs damage such as a break, crack, slit or the like. Further, because the glass substrate has a bigger specific gravity, a disadvantage is produced that the whole apparatus becomes heavy. Therefore, instead of the glass substrate, a plastic substrate is used so as to improve impact ability and to lighten the whole apparatus. 
     However, in the display apparatus using the plastic substrate instead of the glass substrate, because the heat conductivity of the plastic substrate is low so that the heat release performance of the plastic substrate is weak, it is difficult to obtain stable performance and reliability. 
     [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2006-269716 
     SUMMARY OF THE INVENTION 
     It is, therefore, an object of the invention to provide a display apparatus capable of solving the above problem. 
     According to the present invention, there is provided a display apparatus formed by bonding a semiconductor thin film element on a plastic substrate, comprising a thin film metal layer for promoting heat release that is formed on a surface of the semiconductor thin film element. 
     According to the display apparatus of the present invention, because the thin film metal layer formed on the surface of the semiconductor thin film element promotes heat release, it is possible to effectively release heat produced inside the semiconductor thin film element. As a result, it is possible to obtain such a display apparatus having long life, high output and high reliability. 
     The above and other objects and features of the present invention will become apparent from the following detailed description and the appended claims with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a plane drawing showing overall structure of a display apparatus in Embodiment 1. 
         FIG. 2  is a plane enlargement drawing showing a display apparatus in Embodiment 1. 
         FIG. 3  is a sectional enlargement drawing showing a display apparatus in Embodiment 1. 
         FIG. 4  is a plane enlargement drawing of Embodiment 2. 
         FIG. 5  is a sectional enlargement drawing showing a display apparatus in Embodiment 2. 
         FIG. 6  is a plane drawing showing overall structure of a display apparatus in Embodiment 3. 
         FIG. 7  is a plane enlargement drawing showing a display apparatus in Embodiment 3. 
         FIG. 8  is a first sectional enlargement drawing showing a display apparatus in Embodiment 3. 
         FIG. 9  is a second sectional enlargement drawing showing a display apparatus in Embodiment 3. 
         FIG. 10  is a plane drawing showing overall structure of a display apparatus in Embodiment 4. 
         FIG. 11  is a plane enlargement drawing showing a display apparatus in Embodiment 4. 
         FIG. 12  is a first sectional enlargement drawing showing a display apparatus in Embodiment 4. 
         FIG. 13  is a second sectional enlargement drawing a display apparatus in Embodiment 4. 
         FIG. 14  is a plane drawing showing overall structure of a display apparatus in Embodiment 5. 
         FIG. 15  is a sectional enlargement drawing showing a display apparatus in Embodiment 5. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Embodiments of the invention will be described in detail hereinbelow with reference to the drawings. 
     Embodiment 1 
       FIG. 1  is a plane drawing showing overall structure of a display apparatus in Embodiment 1. 
     As shown by  FIG. 1 , a display apparatus  1  of Embodiment 1 is formed by arranging a plurality of thin film LEDs  102  serving as semiconductor thin film elements on a plastic substrate  100  with a matrix manner. Further, anodes in the same queue of the thin film LEDs  102  are connected with a transverse wiring  104  having a connection use pad  108 , and cathodes in the same row of the thin film LEDs  102  are connected with a vertical wiring  103  having a connection use pad  108 . 
       FIG. 2  is a plane enlargement drawing showing a display apparatus in Embodiment 1; and  FIG. 3  is a sectional enlargement drawing showing a display apparatus in Embodiment 1. 
     The  FIG. 3  is an A-A sectional diagram including the thin film LED  102  in the  FIG. 2 . 
     Next is to explain the display apparatus  1  and the thin film LED  102  in detail through using the  FIG. 2  and the  FIG. 3 . 
     As shown by the  FIG. 2 , the display apparatus  1  comprises a plastic substrate  100 , thin film LED  102  serving as semiconductor thin film element, vertical distribution  103 , transverse wiring  104 , interlayer insulation film  105  and connection wiring (transverse)  106 . 
     The plastic substrate  100  is used for mounting the thin film LED  102 , and it is a thin plate made from organic material represented by polyethylene terephthalate (PET). Moreover, as the organic material, polyimide, polycarbonate, polyethylene naphthalate or aramid can also be adopted. The thin film LED  102  is a LED of M dots×N dots formed on the plastic substrate  100  in a thin film shape. The vertical wiring  103  is an electroconductive thin film to connect with a cathode of the thin film LED  102  formed on the plastic substrate  100 . The vertical wiring  103  is a metal wiring obtained through accumulating metal material such as gold or aluminum, or above-stated metal material with nickel, or titanium or the like onto the plastic substrate  100  in a thin film lamination, and it connects with cathodes of respective thin film LEDs  102 . In addition, the vertical wiring  103  and the inner surface electrode  107  are integrated in the present Embodiment. 
     The transverse wiring  104  is an electroconductive thin film to connect with an anode of the thin film LED  102  formed on the plastic substrate  100 . The transverse wiring  104  is a metal wiring obtained through accumulating metal material such as gold or aluminum, or above-stated metal material with nickel, or titanium or the like onto the plastic substrate  100  in a thin film lamination, and it connects with anodes of respective thin film LEDs  102 . 
     The interlayer insulation layer  105  is accumulated for obtaining an interlayer insulation between the vertical wiring  103  and the transverse wiring  104 , e.g. it is an insulation thin film such as oxidation silicon and etc. The connection wiring (transverse)  106  is metal wiring obtained through accumulating metal material such as gold or aluminum, or above-stated metal material with nickel, or titanium or the like used for connecting an upper contact layer  109  ( FIG. 3 ) described below and the transverse wiring  104  onto the plastic substrate  100  in a thin film lamination. 
     As shown by  FIG. 3 , an upper contact layer  109 , an upper clad layer  110 , an active layer  111 , a lower clad layer  112  and a lower contact layer  113  are accumulated. Inclined side surfaces of such layers are covered by the interlayer insulation film  105 , so that the thin film LED  102  is accumulated on the plastic substrate  100  via the inner surface electrode  107 . 
     The inner surface electrode  107  is an electrode for supplying electric field intensity with the upper contact layers  109  in order to make the thin film LED  102  emit light; in the present invention, the inner surface electrode  107  can also be used as a metal layer for effectively releasing heat produced when making the thin film LED  102  emit light. In the present Embodiment, the inner surface electrode  107  is integrated with the vertical wiring  103  ( FIG. 2 ). 
     That is, the thin film LED  102  is characterized in that: it is solidly bonded on the surface of the inner surface electrode  107  serving as a heat release layer, for example, a metal layer of Au, AuGeNi, Al, AlNd, Ti, Ni, Pt, Ag, Pd, Cu and etc.; or for example, a transparent electrode layer of ITO, ZnO2, In2O3 and etc., through intermolecular force of hydrogen bond. Moreover, such heat release layers is formed by well-known vapor deposition method and sputter method, and the heat conductivity is better above 50 W/mK. 
     As mentioned above, because the thin film LED  102  is solidly bonded with the inner surface electrode  107  formed as heat release layer through intermolecular force of hydrogen bond, the bonding surface of the thin film LED  102  and the bonded surface of the plastic substrate are controlled as the surface roughness, that is, the typical height difference between the concave peak or convex peak and valley is about 5 nm below. 
     In order to further strengthen bonding force, it is better to clean and activate these bonding surfaces by an energy wave (e.g. plasma apparatus and so on). Moreover, coating with an active agent is also a method for activating the bonding surface. 
     After LED thin film plurally and integratively generated in a rectangle shape is solidly bonded on the surface of the inner surface electrode  107  formed as a heat release layer by intermolecular force of hydrogen bond, the thin film LED  102  is formed by a photolithographic etching method. 
     The above-stated LED thin film is grown on a GaAs substrate, a sapphire substrate, an InP substrate, a glass substrate, a quartz substrate or a Si substrate via a sacrificial layer by well-known metal organic chemical vapor deposition method (MOVPE method), metal organic vapor phase epitaxy method (MOVPE method), molecular beam epitaxy method (MBE method) and etc. 
     Because the LED thin film (thin film LEDs  102 ) can be thinned to a thickness below e.g. 5 μm, the LED thin film is characterized in an extremely strong flexibility. Moreover, unlike liquid crystal and organic EL, the LED thin film (thin film LEDs  102 ) uses material made by semiconductor epitaxial growth method, material with a high quality and a high reliability. Therefore, it is possible to ensure high quality and high reliability. 
     The LED thin film is formed by epitaxial growth so as to furnish a sacrificial layer capable of performing a selective etching. Through selectively etching the sacrificial layer, a LED thin film is formed by using lift-off method. Moreover, in the case that it is compound semiconductor such as LED elements of GaN system and etc. so that it is difficult to selectively etch the sacrificial layer, as a means to thinning thin film, it is possible to use a treatment to grind the inner surface of substrate. In the case, the LED thin film may be thinned so that a thickness including an epitaxial growth layer needed for LED emitting element is about 50 μm below, the thinned LED thin film may be used as LED emitting element. The LED thin films formed on the flexible substrate can be arranged to form the thin film LED  102  by well-known photolithographic technology. 
     Through injecting current between the transverse wiring  104  and the vertical wiring  103  toward a bias voltage direction, the thin film LED  102  formed on the plastic substrate  100  emits light. Because the thin film LED  102  can be thinned to a thickness below e.g. 5 μm, it can have a flexibility. Even if it is formed on plastic substrate  100 , it can operate as an emitting element capable of ensuring high quality and high reliability. In addition, when thin film LED  102  operates, huge heat happens due to absorption of power that does not contribute to emitting light or emitted light. Here, according to the present invention, the heat can be effectively released toward the outside of the apparatus via the inner surface electrode  107  formed as a heat release layer. 
     Explanation of Effect 
     As mentioned above, through interposing the inner surface electrode  107  formed as heat release layer between the plastic substrate  100  and the thin film LED  102 , it is possible to effectively release heat produced inside the thin film LED  102 . As a result, it is possible to obtain such display apparatus having long life, high output and high reliability. 
     Embodiment 2 
       FIG. 4  is a plane enlargement drawing of Embodiment 2; and  FIG. 5  is a sectional enlargement drawing showing a display apparatus in Embodiment 2. 
     The  FIG. 5  is an A-A sectional diagram including the thin film LED  102  in the  FIG. 4 . 
     Next is to explain the display apparatus  2  and the thin film LED  102  in detail through using the  FIG. 4  and the  FIG. 5 . Moreover, regarding a plane drawing showing overall structure of a display apparatus in Embodiment 2, it is omitted because it is the same as  FIG. 1 . 
     As shown by the  FIG. 4 , the display apparatus  2  comprises a plastic substrate  100 , thin film LED  102  serving as semiconductor thin film element, vertical distribution  103 , transverse wiring  104 , interlayer insulation film  204  and connection wiring (transverse)  106 . The following is only to explain the components different from Embodiment 1, regarding the same components as Embodiment 1, they will be assigned to the same symbols and their explanations will be omitted. 
     The interlayer insulation layer  204  is accumulated for obtaining an interlayer insulation between the vertical wiring  103  and the transverse wiring  104 , e.g. it is an insulation thin film such as oxidation silicon and etc. Further, in the present Embodiment, the interlayer insulation layer  204  also is used as insulation thin film to cover a thick film heat conductive layer  203  ( FIG. 5 ). 
     As shown by  FIG. 5 , an upper contact layer  109 , an upper clad layer  110 , an active layer  111 , a lower clad layer  112  and a lower contact layer  113  are accumulated. Inclined side surfaces of such layers are covered by the interlayer insulation film  204 , so that the thin film LED  102  is accumulated on the plastic substrate  100  via the thick film heat conductive layer  203 . 
     The thick film heat conductive layer  203  is a metal heat release layer with a thickness of 5 μm to 10 μm and is arranged just under a heat region of the thin films LED  102 . As a thickening method, it may be electrolytic plating method; and it also may be a method to pattern as only thickening the heat region. Moreover, as electrolytic plating material, similar to Embodiment 1, many materials are available. However, such material having heat conductivity above 50 W/mK is desired. 
     Similar to Embodiment 1, through injecting current into between the transverse wiring  104  and the vertical wiring  103  toward a bias voltage direction, the thin film LED  102  formed on the plastic substrate  100  emits light. Further, similar to Embodiment 1, because the thin film LED  102  can be thinned to a thickness below e.g. 5 μm, it can have a flexibility. Even if while forming it on plastic substrate  100 , it can operate as emitting element capable of ensuring high quality and high reliability. 
     Then, in Embodiment 2, because the thickened thick film heat conductive layer  203  is furnished just under the heat region, in the region heat concentrates, it is possible to partially increase heat capacity. Therefore, comparing with Embodiment 1, it is possible to process abrupt temperature change and to release heat effectively. 
     Explanation of Effect 
     Through furnishing a thickened metal heat release layer (the thick film heat conductive layer  203 ) just under the heat region of the thin film LED  102 , heat capacity becomes big, so it is possible to process abrupt temperature change and to release heat effectively. 
     Embodiment 3 
       FIG. 6  is a plane drawing showing overall structure of a display apparatus in Embodiment 3. 
     As shown by the  FIG. 6 , in the display apparatus  3  in Embodiment 3, a heat conductive layer  310  and a smooth layer  301  are accumulated on a plastic substrate, and on which a plurality of thin film LEDs  102  are accumulated as semiconductor thin film elements in a matrix manner. Further, anodes in the same queue of the thin film LEDs  102  are connected with a transverse wiring  104  having connection use pad  108 , and cathodes in the same row of the thin film LEDs  102  are connected with a vertical wiring  103  having connection use pad  108 . Furthermore, on the four sides surrounding the display apparatus  3 , a metal frame  303  used for heat release is accumulated. Here, the metal frame  303  used for heat release is a heat release plate to absorb the heat of the thin film LED  102  via the heat conductive layer  310  and release the heat to the air. 
       FIG. 7  is a plane enlargement drawing showing a display apparatus in Embodiment 3; and  FIG. 8  is a first sectional enlargement drawing showing a display apparatus in Embodiment 3. 
     The  FIG. 8  is an A-A sectional diagram including the thin film LED  102  in the  FIG. 7 . 
     Next is to explain the display apparatus  3  and the thin film LED  102  in detail through using the  FIG. 7  and the  FIG. 8 . 
     As shown in  FIG. 7 , a display apparatus  3  comprises a thin film LED  102  accumulated on the heat conductive layer  310  ( FIG. 8 ) and the smooth layer  301  placed on the plastic substrate  100  in a matrix form, as semiconductor thin film element; a vertical wiring  305 , a transverse wiring  104 , an interlayer insulation film  105 , a connection wiring (transverse)  106  and a connection wiring (vertical)  308 . The following is only to explain the components different from Embodiment 1, regarding the same components as Embodiment 1, they will be assigned to the same symbols and their explanations will be omitted. 
     The heat conductive layer  310  ( FIG. 8 ) is a metal layer accumulated on the plastic substrate  100  for releasing heat the thin film LED  102  produced; and made of, for example, Au, AuGeNi, Al, AlNd, Ti, Ni, Pt, Ag, Pd, Cu and etc. It is formed by well-known vapor deposition method and sputter method. And the heat conductivity of the heat conductive layer  310  is better above 50 W/mK. 
     The smooth layer  301  is a smooth coating layer accumulated for controlling the surface roughness, that is, the typical height difference between the concave peak or convex peak and valley below about 5 nm. In order to increase heat conductivity between the thin film LED  102  and the heat conductive layer  310  without shutting off, the smooth layer  301  is set below 2 μm. Generally, the smooth layer  301  better adopts organic compound materials, oxide materials or nitride material and is formed by well-known chemical vapor deposition method (CVD method), spin coating method, slit coating method, solution-soaking coating method and spray coating method. 
     The vertical wiring  305  is an electroconductive thin film to connect with cathode of the thin film LED  102  formed on the plastic substrate  100 . The vertical wiring  305  is a metal wiring obtained through accumulating metal material such as gold or aluminum, or above-stated metal material with nickel, or titanium or the like onto the plastic substrate  100  in a thin film lamination, and it electrically connects with cathodes of respective thin film LEDs  102 . In present Embodiment, the vertical wiring  305  is not directly connected with cathode of the thin film LED  102 , but is connected with the cathode of the thin film LED  102  via the connection wiring (vertical)  308 . 
     As shown by  FIG. 8 , the upper contact layer  109 , the upper clad layer  110 , the active layer  111 , the lower clad layer  112  and the lower contact layer  113  are accumulated. The thin film LED  102  whose inclined side surface is covered by the interlayer insulation film  105  is accumulated on the heat conductive layer  302  and the smooth layer  301  accumulated on the plastic substrate  100 . In present Embodiment, the vertical wiring  305  is not directly connected with the lower contact layer  113  of the thin film LED  102 , but is connected with the lower contact layer  113  via the connection wiring (vertical)  308 . 
     In Embodiment, similar to Embodiments 1 and 2, through injecting current into wiring, cathode and anode toward a bias voltage direction, the thin film LED  102  formed on the plastic substrate  100  emits light. Further, because the thin film LED  102  can be thinned to a thickness below e.g. 5 μm, it can have a flexibility. Even if forming it on plastic substrate  100 , it can operate as emitting element capable of ensuring high quality and high reliability. 
     Moreover, similar to Embodiment 1 and Embodiment 2, because formed the heat conductive layer  310  on the inner surface of the thin film LED  102 , it is possible to effectively release heat produced by action of the thin films LED  102 . In the present Embodiment, through coating the smooth layer  301  on the heat conductive layer  310 , not only the functions in Embodiment 1 and Embodiment 2 can be obtained, but also it is possible to improve surface smoothness and obtain more solid bonding. 
     Explanation of Effect 
     In Embodiment 1 and Embodiment 2, through directly bonding the thin films LED  102  on the heat release layer (the inner surface electrode  107 ) and the thickened metal layer (the thick film heat conductive layer  203 ), the heat produced by the thin films LED  102  can be effectively released via these layers. However, in order to adjust surface roughness of such layers to below the 5 nm, enough attention must be paid with respect to film forming condition and film forming apparatus etc. And quality requirements for such films are also extremely strict. According to Embodiment, through coating the smooth layer  301  on the inner surface electrode  107 , it is possible to easily adjust surface roughness to below 5 nm except the effect achieved in Embodiment 1. Therefore, it is possible to solidly bond the thin film LED  102  on the heat conductive layer  310 . 
     The following explains expansion example of Embodiment. 
       FIG. 9  is a second sectional enlargement drawing showing a display apparatus in Embodiment 3. 
     In the display apparatus  3  of Embodiment 3, a smooth layer is furnished between the inner surface electrode  107  ( FIG. 3 ) and the thin films LED  102  ( FIG. 3 ) of the display apparatus  1  in Embodiment 1. However, in the present expansion example, the smooth layer is furnished between the thick film heat conductive layer  203  ( FIG. 5 ) and the thin films LED  102  ( FIG. 5 ) of the display apparatus in Embodiment 2. In the case, through coating the surface of the thick film heat conductive layer  203  ( FIG. 5 ), it is possible to easily adjust the surface roughness to below 5 nm. As a result, it is possible to solidly bond the thin film LED  102  ( FIG. 5 ) on the thick film heat conductive layer  203  ( FIG. 5 ). 
     Embodiment 4 
       FIG. 10  is a plane drawing showing overall structure of a display apparatus in Embodiment 4. 
     As shown by the  FIG. 10 , in the display apparatus  4  in Embodiment 4, a plurality of thin film LEDs  402  are arranged as semiconductor thin film elements in a matrix manner. Further, anodes in the same queue of the thin film LEDs  402  are connected with a transverse wiring  104  having connection use pad  108 , and cathodes in the same row of the thin film LEDs  402  are connected with a vertical wiring  403  having connection use pad  108 . 
       FIG. 11  is a plane enlargement drawing showing a display apparatus in Embodiment 4. 
     As shown in  FIG. 11 , a display apparatus  4  comprises a plastic substrate  100 , a thin film LED  402  serving as semiconductor thin film element; a vertical wiring  403 , a transverse wiring  104 , an interlayer insulation film  105 , and a connection wiring (transverse)  106 . 
       FIG. 12  is a first sectional enlargement drawing showing a display apparatus in Embodiment 4. 
     The  FIG. 12  is an A-A sectional diagram including the thin film LED  402  in the  FIG. 12 . 
     Next is to explain the display apparatus  4  and the thin film LED  402  in detail through using the  FIG. 11  and the  FIG. 12 . 
     As shown in  FIG. 11 , a display apparatus  4  comprises a plastic substrate  100 , a thin film LED  402  serving as semiconductor thin film element; a vertical wiring  403 , a transverse wiring  104 , an interlayer insulation film  105 , and a connection wiring (transverse)  106 . The following is only to explain the components different from Embodiments 1 to 3, regarding the same components as Embodiments 1 to 3, they will be assigned to the same symbols and their explanations will be omitted. 
     The vertical wiring  403  is an electroconductive thin film to connect with cathode of the thin film LED  402  formed on the plastic substrate  100 . The vertical wiring  403  is a metal wiring obtained through accumulating metal material such as gold or aluminum, or above-stated metal material with nickel, or titanium or the like onto the plastic substrate  100  in a thin film lamination, and it electrically connects with cathodes of respective thin film LEDs  402 . In the present Embodiment, the vertical wiring  403  is not directly connected with the cathode of the thin film LED  402 , but is connected with the cathode of the thin film LED  402  via a heat conductive layer and connection wiring  408  ( FIG. 12 ). 
     As shown by  FIG. 12 , an upper contact layer  109 , an upper clad layer  110 , an active layer  111 , a lower clad layer  112  and a lower contact layer  113  are accumulated. The thin film LED  402  whose inclined side surface is covered by the interlayer insulation film  105  and the heat conductive layer and connection wiring  408  is accumulated on the plastic substrate  100 . 
     The heat conductive layer and connection wiring  408  is a thin film metal layer to cover the whole thin film LED  402  from the surface side. The thin film metal layer can be formed by a lengthy pattern of anode or cathode, also can be formed from a pattern completely separated from two poles. Moreover, the thin film metal layer can be formed by well-known vapor deposition method or sputter method; and it can be formed simultaneously with formation of anode or cathode. Considering the heat release performance of the thin film metal layer, the heat conductivity of the thin film metal layer is better above 50 W/mK. 
     In Embodiments 1 to 3, through improving the heat release performance from surface side of the thin film LED  402 , as the element structure of the thin film LED  402  according to Embodiments 1 to 3, without furnishing a heat release layer between the thin film LED  402  and the plastic substrate  100 , the heat release performance can be improved. Further, as explained in Embodiments 1 to 3, through furnishing a multiple heat release layer between the thin film LED  402  and the plastic substrate  100 , the heat release performance can be more improved. 
     In Embodiment, similar to Embodiments 1 to 3, through injecting current into wiring, cathode and anode toward a bias voltage direction, the thin film LED  402  formed on the plastic substrate  100  emits light. Further, because the LED thin film (thin film LED  402 ) can be thinned to a thickness below e.g. 5 μm, it can have a flexibility. Even if forming it on plastic substrate  100 , it can operate as emitting element capable of ensuring high quality and high reliability. 
     Explanation of Effect 
     As explained above, according to the present Embodiment, the heat produced by action of the thin film LED  402  can be effectively released via the heat conductive layer and connection wiring  408  furnished on the element surface side. Moreover, not only the heat conductive layer and connection wiring  408  can be formed as a lengthy pattern of anode or cathode, but also the heat conductive layer and connection wiring  408  can be formed as a pattern completely separated from two poles. Therefore, while forming the anode or the cathode, it is possible to simultaneously form the two poles to obtain such effect. Moreover, differently from Embodiments 1, 2 and 3, because the heat conductive layer and connection wiring  408  is formed on element surface of the thin film LED  402 , it is possible to perform a material selection without considering a bonding strength with the plastic substrate  100 . Furthermore, because the modes described with respect to Embodiments 1, 2 and 3 can be used in multiple, it is possible to further obtain an improved heat release performance. 
     The following explains expansion example of Embodiment. 
       FIG. 13  is a second sectional enlargement drawing a display apparatus in Embodiment 4. 
     In the display apparatus  4  of Embodiment 4, the heat conductive layer and connection wiring  408  is accumulated on the element surface side of the thin film LED  102  ( FIG. 8 ) of the display apparatus  3  of Embodiment 3. However, in the expansion example, it is to accumulate a heat conductive layer  415  on the element surface side of the thin film LED  102  ( FIG. 3 ) of the display apparatus  1  in Embodiment 1. In the case, the same effects as Embodiment 4 can be obtained. 
     Embodiment 5 
       FIG. 14  is a plane drawing showing overall structure of a display apparatus in Embodiment 5. 
     As shown by the  FIG. 14 , in a display apparatus  5  of Embodiment 5, a plurality of thin film LEDs  502  are accumulated as semiconductor thin film elements on the plastic substrate  100 . Subsequently, on which a passivation film  503  (as described below) and a heat conductive layer  501  are accumulated as covering the whole display apparatus  5 . The following is only to explain the components different from Embodiments 1 to 4, regarding the same components as Embodiments 1 to 4, they will be assigned to the same symbols and their explanations will be omitted. 
       FIG. 15  is a sectional enlargement drawing showing a display apparatus in Embodiment 5. 
     As shown by  FIG. 15 , an upper contact layer  109 , an upper clad layer  110 , an active layer  111 , a lower clad layer  112  and a lower contact layer  113  are accumulated. The thin film LED  502  whose inclined side surface is covered by an interlayer insulation film  105 , the passivation film  503  and the heat conductive layer  501  is accumulated on the plastic substrate  100 . 
     The passivation film  503  is an insulation layer composed of a transparent oxide film or a transparent nitride film formed on element surface. The passivation film  503  must not shut off a heat conduction toward the heat conductive layer  501  with high heat conductivity placed on passivation film  503 . Therefore, the passivation film  503  is better to have a film thickness above 500 nm. Moreover, the oxide film and nitride film can be formed by well-known plasma CVD method or sputter method. 
     The heat conductive layer  501  is a film with high heat conductivity accumulated on the passivation film  503 . The heat conductive layer  501  is composed of a transparent conductive film such as ITO, ZnO 2 , In 2 O 3  and other, or an organic compound material with conductivity. Further, the heat conductive layer  501  can use metal material such as Au, Al and other to form film below e.g. 10 nm. Such films can be formed by well-known sputter method, vapor deposition method, spin coating method, slit coating method, solution-soaking coating method and spray coating method. 
     In Embodiment, similar to Embodiments 1 to 4, through injecting current into among wiring, cathode and anode toward a bias voltage direction, the thin film LED  502  formed on the plastic substrate  100  emits light. Further, like Embodiment 1, because the LED thin film (thin film LED  502 ) can be thinned to a thickness below e.g. 5 μm, it can have a flexibility. Even if while forming it on plastic substrate  100 , it can operate as emitting element capable of ensuring high quality and high reliability. 
     In the element structure of the present Embodiment, because a layer for releasing heat as covering a whole surface of the element is furnished, the heat produced by action of the thin film LED  502  can be released via a layer (heat conductive layer  501 ) with high heat conductivity. Moreover, through using element structures of Embodiments 1 to 4 in multiple, it is possible to further effectively release heat from the surface side and the inner surface side of the thin film LED  502 . 
     Explanation of Effect 
     As explained above, according to the present Embodiment, because the heat produced by action of the thin film LED  402  can be effectively released via the heat conductive layer  501  with high heat conductivity for releasing heat, furnished on the element surface side, so heat release efficiency can be improved. Moreover, according to the present Embodiment, the heat conductive layer  501  is furnished on the thin film LED  502  via the passivation film  503 , it is possible to form the heat conductive layer  501  as covering the whole element of the thin film LED  502  without patterning. Therefore, a simple manufacturing method can be supplied. 
     In the above stated Embodiments, it only explained that the present invention is applied to display apparatuses adopting a thin film LED. However, the present invention is not limited to the case, i.e. the present invention also can be applied to any display apparatuses comprising a semiconductive element capable of being accumulated on a plastic substrate. 
     The present invention is not limited to the foregoing Embodiments but many modifications and variations are possible within the spirit and scope of the appended claims of the invention.