Abstract:
Disclosed is a method for sealing a light-emitting device wherein formation of air bubbles in a light-emitting device module can be prevented by performing no gelation after fitting of a cover member. This method also enables to seal a light-emitting device by using a gel sealing material composed of a gel precursor which uses a solvent. Also disclosed is a light-emitting module formed by such a sealing method. In this method for sealing a light-emitting device, gelation of the gel precursor of a gel sealing material is performed before placing the precursor on the light-emitting device, and thus no gelation is necessary after fitting of a cover member. Consequently, a gel precursor having high viscosity that is difficult to be used in an injection method can be used in this method. Furthermore, a substance which requires use of a solvent can be used as a gel precursor of a gel sealing material. A light-emitting device module with high luminance wherein no air bubbles are included can be obtained by this method.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is a national stage of International Application No. PCT/JP2006/304589 filed on Mar. 9, 2006 and claims priority to Japanese Patent Application No. 2005-214842 filed on Jul. 25, 2005, the disclosures of which are incorporated herein by reference. 
     BACKGROUND 
     The present invention relates to a method for sealing a light emitting element using a gel sealant made by causing a gel precursor to gel to lose liquidity, and further relates to a light emitting element module formed by this method. 
     The light emitting element module, such as a light emitting diode (LED) or the like, has properties such as having low power consumption, being miniature, being lightweight, and the like, and is used as a light source of a printer head, a light source of a liquid crystal backlight, a light source of various types of meters, and the like. 
     As an example of such a light emitting element module, as shown in  FIG. 7 , there is a light emitting element module containing a light emitting element  90 , a base  91  having a concave portion in which the light emitting element  90  is stored, a lid  92  covering the light emitting element  90 , and a silicone gel  93 , for sealing the light emitting element  90 , disposed between the base  91  and the lid  92 . 
     The silicone gel  93  for sealing the light emitting element  90  gels by mixing two types of liquids and applying heat thereto. The gelling reaction of the two types of liquids is achieved by applying heat of 80 degrees Celsius to 150 degrees Celsius, thereby forming the silicone gel  93 . 
     One method for sealing the light emitting element involves placing the light emitting element  90  on the base  91 , thereafter unifying the lid  92  and the base  91 , and, as shown in  FIG. 7 , mixing and injecting the two types of liquids making up the silicone gel  93  into between the lid  92  and the base  91  using an injector  94 , and then heating the liquids. At this time, the mixture of the two types of liquids is injected until overflowing, so that air bubbles causing a decrease in light output or the like are not mixed in. 
     Furthermore, there is another method for sealing the light emitting element upon storing the light emitting element in the concave portion of the base, injecting the soft material thereon, placing on the soft material the lid protruding in a direction of the light emitting element, and thereafter applying heat thereto to unify the lid, the soft material, and the base (see, e.g., Patent Document 1). The soft material is injected through potting, and thus is fluidic, but the heat applied after the lid is placed causes the soft material to gel.
         Patent Document 1: Japanese Unexamined Patent Application Publication No. 2003-318448       

     Through the method for mixing two types of liquids while injecting the mixture with the injector  94 , however, the liquid must be injected until overflowing to prevent air bubbles between the base  91  and the lid  92 . In other words, the overflowing liquid is wasted. The method raises another problem that it is difficult to align a tip of the injector  94  with injection entrance for injecting the two types of liquids between the base  91  and the lid  92 . 
     Furthermore, heating is necessary for the two types of liquid that become the silicone gel  93  to gel. In other words, it is necessary to use a material for the base  91 , the lid  92 , and the like that can withstand the heat required to cause the two types of liquids to gel, thereby limiting the material that can be used. Furthermore, through such a method, a substance using a solvent cannot be used as the gel precursor of the gel because such a solvent causes air bubbles when evaporated, thereby decreasing the light output. 
     On the other hand, in the method for sealing the light emitting element of Patent Document 1, by placing the lid that protrudes in a direction of the light emitting element, air bubbles can be prevented from arising in the fluidic soft material. Determining a location at a time when the viscous soft material is injected thereby becomes relatively easy. The method of Patent Document 1, however, requires heat to cause the soft material to gel and does not allow the use of a solvent for the gel precursor of the soft material, thus leaving unsolved problems. 
     SUMMARY 
     It is an object of the present invention, in consideration of the aforementioned situation, to provide a method for sealing a light emitting element without executing gelling after the lid is affixed, which can seal the light emitting element with a gel sealant made from a gel precursor using a solvent while preventing formation of air bubbles in a light emitting element module, and further, to provide a light emitting element module formed through the aforementioned sealing method. 
     A method for sealing a light emitting element according to the present invention is a method for sealing a light emitting element with a gel sealant that has lost fluidity by gelling of a gel precursor, and contains the steps of causing the gel precursor to gel to form the gel sealant, placing the formed gel sealant on the light emitting element, placing a lid on the gel sealant to sandwich the gel sealant between the lid and the light emitting element, and pressing the lid toward the light emitting element. 
     Through the method for sealing the light emitting element of the present invention, the gel precursor of the gel sealant gels and loses fluidity before the lid is placed on the light emitting element, so that gelling is unnecessary after the lid is affixed. Therefore, a highly viscous gel precursor, which would be difficult to be handled in an injection method, can be used. Furthermore, a substance using a solvent can be used as the gel precursor of the gel sealant. 
     In the method for sealing the light emitting element of the present invention, the gel sealant is pressed against the light emitting element before the lid is placed on the gel sealant to prevent air bubbles from being mixed in between the light emitting element and the gel sealant. 
     In the method for sealing the light emitting element of the present invention, at the step where the lid is pushed toward the light emitting element, the lid is pressed with a pressing section under reduced pressure. By lowering the ambient pressure around the light emitting element, air bubbles are prevented from being mixed in between the light emitting element and the gel sealant and between the gel sealant and the lid. 
     In the method for sealing the light emitting element of the present invention, at the step where the gel sealant is pushed against the light emitting element, the gel sealant, having a position aligned with that of the LED element, is pressed continuously from one end thereof to the other end thereof. Therefore, because the gel is pressed in a manner to push out air bubbles from between the gel sealant and the light emitting element, air bubbles are prevented from being mixed in between the light emitting element and the gel sealant. 
     In the method for sealing the light emitting element of the present invention, at the step where the gel sealant is formed by causing the gel precursor to gel, the gel precursor is formed on a prescribed separating sheet in a film shape or in a shape corresponding to a shape of the lid, after which, the gel precursor is caused to gel to form the gel sealant and the formed gel sealant is removed from the separating sheet. Therefore, the formed gel sealant can be easily handled. 
     In the method for sealing the light emitting element of the present invention, the gel sealant has a ratio (tan δ=G″/G′) of a storage elastic modulus (G′) and a loss elastic modulus (G″), determined according to a viscoelastic measurement, less than or equal to 1. For example, where sine wave torsional strain is applied to the gel precursor and the dynamic stress of the gel precursor is measured with a rotating rheometer while the temperature of the gel precursor is gradually increased, the tan δ value of the gel precursor quickly decreases to be less than or equal to 1 at around a gelling temperature. In other words, in a case where the tan δ derived by the viscoelastic measurement is less than or equal to 1, it is certain that the gel precursor has gelled to became a non-fluidic gel. Accordingly, by using the gel sealant having a tan δ value less than or equal to 1, it is not necessary to execute gelling after the lid is placed, so that the substance using the solvent can be used as the gel precursor. 
     In the method for sealing the light emitting element of the present invention, the gel sealant is a compound of polyvinylidene-fluoride resin dissolved into a medium. The refractive index of the compound of polyvinylidene-fluoride resin dissolved into the medium is greater than the refractive index of silicone, which is often used as the gel sealant. Therefore, even in a case where a lid having a relatively high refractive index is used, by using such a substance having a high refractive index as the gel sealant, the difference between the refractive index of the gel sealant and the refractive index of the lid is decreased, thereby increasing brightness of the light emitted from the sealed light emitting element. 
     Furthermore, the light emitting element module of the present invention contains the light emitting element, the gel sealant that has lost fluidity by gelling of the gel precursor, and the lid sandwiching the gel sealant between the lid and the light emitting element. In the light emitting element module of the present invention, the formed gel sealant is placed on the light emitting element, the lid is placed on the gel sealant, and the light emitting element is sealed by pressing the lid toward the light emitting element. 
     Through the light emitting element module of the present invention, the gel precursor of the gel sealant gels and loses fluidity before the gel sealant is placed on the light emitting element, so that gel sealant need not be subjected to a gelling step such as heating after the light emitting element is sealed. Therefore, a highly viscous gel precursor, which would be difficult to be handled in an injection method, can be used. Furthermore, a substance using a solvent can be used as the gel precursor of the gel sealant. In such a manner, the light emitting element module having a high degree of brightness and in which air bubbles are not mixed in is provided. 
     In the light emitting element module of the present invention, the gel sealant has a ratio (tan δ=G″/G′) of a storage elastic modulus (G′) and a loss elastic modulus (G″), determined according to a viscoelastic measurement, less than or equal to 1. By using the gel sealant with a tan δ value less than or equal to 1, it is not necessary to execute gelling after the lid is placed. In other words, the light emitting element module in which air bubbles are not mixed in is provided. 
     In the light emitting element module of the present invention, the gel sealant is a compound of polyvinylidene-fluoride resin dissolved into a medium. The refractive index of the compound of polyvinylidene-fluoride resin dissolved into the medium is greater than the refractive index of silicone, which is often used as the gel sealant. Therefore, even in a case where a lid having a relatively high refractive index is used, by using such a substance having a high refractive index as the gel sealant, the difference between the refractive index of the gel sealant and the refractive index of the lid is decreased, thereby providing the light emitting element module having a high degree of brightness. 
     In the method for sealing the light emitting element according to the present invention as described above, the gel precursor of the gel sealant gels and loses fluidity before the gel sealant is placed on the light emitting element, so that the gel sealant need not be caused to gel after the lid is affixed. Therefore, a highly viscous gel precursor, which would be difficult to be handled in an injection method, can be used. Furthermore, a substance using a solvent can be used as the gel precursor of the gel sealant. 
     Furthermore, through the light emitting element module of the present invention as described above, the gel precursor of the gel sealant gels and loses fluidity before the gel sealant is placed on the light emitting element, so that the gel sealant need not be subjected to a gelling step such as heating after the light emitting element is sealed. Therefore, a highly viscous gel precursor, which would be difficult to be handled in an injection method, can be used. Furthermore, a substance using a solvent can be used as the gel precursor of the gel sealant. In such a manner, the light emitting element module having a high degree of brightness and in which air bubbles are not mixed in is provided. 
     Additional features and advantages of the present invention are described in, and will be apparent from, the following Detailed Description and the Figures. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  is a diagram showing an example of a light emitting element module containing a light emitting element sealed by the method for sealing a light emitting element according to the present invention; 
         FIG. 2  is a diagram describing a method for forming a gel sealant used in the method for sealing the light emitting element according to the present invention; 
         FIG. 3  is a diagram describing a step of placing the gel sealant on the light emitting element in the method for sealing the light emitting element according to the present invention; 
         FIG. 4  is a diagram describing a step of pressing a translucent lens toward the light emitting element in the method for sealing the light emitting element according to the present invention; 
         FIG. 5  is a diagram describing an example of the step of pressing a translucent lens toward the light emitting element in the method for sealing the light emitting element according to the present invention; 
         FIG. 6  is a diagram describing another example of the step of pressing a translucent lens toward the light emitting element in the method for sealing the light emitting element according to the present invention; and 
         FIG. 7  is a diagram describing a step of injecting a gel precursor of the gel sealant according to a conventional method for sealing the light emitting element. 
     
    
    
     DETAILED DESCRIPTION 
     The following is a description of the light emitting element module and method for sealing a light emitting element according to the present invention using a light emitting diode (LED) as an example of the light emitting element. The present invention is not limited to the following description, and may be arbitrarily altered without deviating from the general scope of the invention. 
     The sealing method of the present invention includes causing a gel precursor to gel to form a gel sealant, placing the formed gel sealant on the LED element, placing the lid on the gel sealant, and pressing the lid toward the LED element. 
       FIG. 1  is a diagram showing an LED element module including the LED element sealed according to the sealing method of the present invention. An LED element module  1  contains an LED element  10  serving as the light emitting element, a base  20  storing the LED element  10 , a gel sealant  30  for sealing the LED element  10 , and a translucent lens  40  serving as the lid placed on the gel sealant  30 . 
     The LED element  10  is a chip-shaped light emitting element stored in a concave portion  21  of the base  20 . The LED element  10  contains electrodes, not shown, on a surface thereof. A location of the electrodes is not particularly limited, but, for example, may be a pair of positive and negative electrodes on an upper surface of the LED element  10 . In such a case, as shown in  FIG. 1 , the pair of electrodes are connected to lead wires  22  of the base  20  by wires  11 . Accordingly, by connecting the lead wires  22  of the base  20  to a substrate, not shown, the LED element  10  is energized and can emit light. A method of wiring is not particularly limited. The wires  11  are not particularly limited and, for example, may use material having a low electrical resistance such as gold or copper, and an outer surface of the wires  11  may be coated with a resin or the like to increase mechanical strength of the wires  11 . 
     The LED element  10  is formed by laminating n-type and p-type semiconductors to form a p-n junction. Then, by applying voltage to the p-n junction via the n-type electrode and p-type electrode formed on the surface of the LED element  10 , light having a prescribed wavelength is emitted from the p-n junction. Semiconductors such as GaP, GaAs, GaAsP, GaAlAs, GaN, SiC, or the like are exemplified as the semiconductors of the LED element  10 . 
     The base  20 , as described above, contains a concave portion for storing the LED element  10 . In an internal portion of the concave portion, the lead wires  22 , which are connected to the pair of electrodes of the LED element  10  via the wires  11 , are formed in a protruding manner. Furthermore, a heat sink  23  is disposed in a lower portion of the LED element  10  to externally release heat generated by the light emission of the LED element  10 . A shape of the base  20  is different depending on the translucent lens  40 , but the shape is not particularly limited as long as the shape is such that the lid  20 , together with the translucent lens  40 , can sandwich and enclose the gel sealant  30  and the LED element  10 . For example, in a case where the translucent lens  40  is a dome shape, a base  20  having a flat board shape may be used. 
     The gel sealant  30  is translucent and is a sealant for sealing the LED element  10 . The gel sealant  30  has an appropriate amount of softness to protect the LED element  10  and the wire  11  from wetness, shock, or the like. Furthermore, the gel sealant  30  makes it difficult to transmit to the translucent lens  40  the heat generated by the emission of light from the LED element  10 , so that degradation of the translucent lens  40  by heat can be prevented. 
     The gel precursor gels and loses fluidity to become the gel sealant  30  before being placed on the LED element  10 . The present invention allows the use of a gel precursor including a solvent because formation of the gel sealant  30  from the gel precursor is executed before placement on the LED element  10 , whereas conventional method does not allow the use of such a gel precursor including a solvent because the solvent results in air bubbles. 
     The gel precursor is a composition that forms the gel sealant  30  by gelling, but this composition is not particularly limited. The gel precursor is usually a reactive composition made by mixing one or more of a polymer, an oligomer, or a monomer having polymerizable group with a catalyst, a polymerization initiator, a hardening agent, a polymerization inhibitor, a medium, a particle having high refractive index, or the like. For example, in a case where a silicone resin is used as the gel sealant  30 , the silicone resin is obtained by mixing a siloxane compound having a vinyl group with a siloxane compound having an SiH group, adding a catalyst such as platinum or the like thereto, and applying heat thereto. An oligomer or polymer such as a dimethyl siloxane, a methylphenyl siloxane, a diphenyl siloxane, or the like is used as the siloxane compound. Furthermore, such oligomer or polymer may be homopolymer or copolymer. Yet further, the compound may be a compound that exhibits sol-gel transformation through heating, such as a compound made by dissolving into a medium a polymer having a physical cross-linking property. At high temperatures, such a compound becomes a solution and can be treated as the gel precursor, and at low temperatures, can be treated as the gel sealant. For example, the compound can be polyvinylidene-fluoride resin or polyhexafluoropropylene resin dissolved into a medium. The above medium means a liquid into which polyvinylidene-fluoride or polyhexafluoropropylene resin is dissolved, and includes a solvent having a relatively low boiling point such as toluene, methyl ethyl ketone, methyl isobutyl ketone, acetone, cyclohexane, cyclohexanone, or a liquid having a relatively high boiling point such as polyethyleneglycol or silicone oil. The compound made by dissolving the polyvinylidene-fluoride resin or polyhexafluoropropylene resin into the medium has a refractive index greater than that of silicone conventionally used as the gel sealant. Accordingly, even where the translucent lens  40  having a high refractive index is used, a difference between the gel sealant  30  and the translucent lens  40  is decreased by using such a material having a high refractive index as the gel sealant  30 , so that brightness of the light emitting element is increased. 
     The gel sealant  30  may be formed by mixing into the gel precursor a substance altering a refractive index, altering a color of the light emitted from the LED element  10 , or the like. For example, by mixing compound powder including sulfur atoms, nanoscale oxidized titanium particles, or the like into the gel precursor, the refractive index of the thusly formed gel sealant  30  can be adjusted. To mix in the compound powder containing the sulfur atoms, it is necessary to dissolve the gel precursor and the compound powder containing the sulfur atoms into the solvent. According to the sealing method of the present invention, the solvent is removed at a time when the gel sealant  30  is formed, that is, before being placement on the LED element  10 . Accordingly, the solvent used in the gel precursor of the gel sealant  30  is not a source of air bubbles. Furthermore, viscosity of the gel precursor is increased where the oxidized titanium particles are used, but the increased viscosity is not a problem because the gel precursor is not injected after the lens is affixed, unlike the conventional method, and instead the gel sealant  30  is placed on the LED element  10  after the gel sealant  30  is formed into the prescribed shape. 
     The gel sealant  30  is not particularly limited as long as it is a translucent and flexible gel sealant. For example, a gel made from conventionally used silicone resin may be used as the gel sealant  30 . The silicone resin gels and loses fluidity to become a gel before the gel precursor of the gel sealant  30  made from the silicone resin is placed on the LED element  10 . Accordingly, it is not necessary to execute gelling by heat or the like after the translucent lens  40  is placed on the gel sealant  30 . Furthermore, even where the substance to alter the refractive index of the gel sealant  30  is mixed into the gel precursor and increases the viscosity of the gel precursor, the increased viscosity does not raise a problem. 
     Furthermore, a gel made from a compound of polyvinylidene-fluoride resin dissolved in the medium is exemplified as a material other than the silicone resin. Thereby, even in a case where the translucent lens  40  having a relatively high refractive index is used, by using such material having a very high refractive index as the gel sealant  30 , the difference between the refractive index of the gel sealant  30  and the refractive index of the translucent lens  40  is decreased, so that the brightness of the formed light emitting element module can be increased. The material of the gel sealant can be arbitrarily selected depending on the relation between the refractive index of the gel sealant  30  and the refractive index of the translucent lens  40 , the flexibility of the gel sealant  30 , and the like. 
     It is desirable that the solvent used in the gel precursor evaporates when heated, but the solvent is not particularly limited thereto, and any solvent necessary to form the gel sealant  30  can be used. For example, toluene, methyl ethyl ketone, methyl isobutyl ketone, acetone, cyclohexane, cyclohexanone, or the like can be used. The solvent can be evaporated at a time when the gel sealant  30  is formed, that is, at a time of gelling of the gel precursor. Furthermore, even where the solvent is not completely evaporated at a time when the gel precursor is gelled, the solvent can be evaporated before the gel sealant  30  is placed on the LED element  10 . 
     The gel precursor is made to lose fluidity, for example, by being heated to form the gel sealant  30  that has gelled. At this time, it is desirable that the gel sealant  30  have a ratio (tan δ=G″/G′) of a storage elastic modulus (G′) and a loss elastic modulus (G″), determined according to a viscoelastic measurement, less than or equal to 1. The storage elastic modulus (G′) and the loss elastic modulus (G″) can be determined according to a viscoelastic measurement and the ratio tan δ can be calculated by tan δ=G″/G′. A tan δ value greater than 1 represents that the gel precursor still possesses fluidity, and has therefore not yet become the gel sealant  30 . Where the material having a tan δ value greater than 1 is placed on the LED element, it is necessary to execute reheating or the like to gel the material after the translucent lens  40  is pressed toward the LED element  10 . In other words, such a gel precursor using the solvent cannot be used in this case. On the other hand, a tan δ value less than or equal to 1 represents that the gel precursor does not possess fluidity, and has therefore become the gel sealant  30  of the present invention. Accordingly, it is not necessary to execute gelling after the translucent lens  40  is pressed toward the LED element  10 . Therefore, such a substance using the solvent can be used as the gel precursor. 
     In addition, it is desirable that the gel sealant  30  has approximately the same refractive index as the translucent lens  40 . The gel sealant  30 , sealing the LED element, having approximately the same refractive index as the translucent lens  40  reduces the reflection of the light emitted from the LED element  10  at the interface between the gel sealant  30  and the translucent lens  40 . In other words, an amount of light put out from the LED element module  1  is increased, thereby increasing the brightness. For example, in a case where the refractive index of the used translucent lens is 1.7, the refractive index of the sealant  30  can be adjusted to be near the refractive index of the translucent lens  40 , which is 1.7, by mixing in a material of the gel sealant  30  or a prescribed substance, so that the brightness of the thusly formed LED element module  1  is increased. 
     The translucent lens  40  serving as the lid has mechanical strength and translucency and is placed on the gel sealant  30  to sandwich the gel sealant  30  together with the LED element  10 . The translucent lens  40  directs the light emitted from the LED element  10  in a direction of an upper surface, a direction of a side surface, or the like in relation to the LED element  10 , and can thereby output the light in a prescribed direction. 
     The translucent lens  40 , together with the base  20 , sandwiches and encloses the LED element  10  and the gel sealant  30 , thereby uniting the LED element  10 , the base  20 , the gel sealant  30 , and the translucent lens  40 . For example, the translucent lens  40  may be engaged with the base  20  to form the unified body. Furthermore, in a case where the gel sealant  30  is adhesive, the LED element  10 , the base  20 , the gel sealant  30 , and the translucent lens  40  may be united by the gel sealant  30 . The LED element  10  can thereby be sealed by the gel sealant  30  to form the LED element module  1 . The shape of the translucent lens  40  may be in any shape as long as the light can be put out in a prescribed direction, as described above. For example, a dome shape shown in  FIG. 1  or a convex lens shape may be used. The material forming the translucent lens  40  can be, for example, a glass, a transparent resin, or the like having superior weather resistance, such as an epoxy resin, an acrylic resin, a silicone resin, a polycarbonate resin, or a cycloolefin resin. 
     First, in the method for sealing the light emitting element according to the present invention, gelling of the gel precursor of the gel sealant  30  is executed. Conditions of gelling can be arbitrarily changed according to the formed gel sealant  30  and the gel precursor thereof. For example, in a case where silicone resin is used, the gel precursor is hardened by heat of 150 degrees Celsius, which may vary depending on the gel precursor, thereby forming the gel made up of the silicone resin. 
     To seal the LED element  10 , the thusly formed gel sealant  30  has a prescribed shape corresponding to the shape of the base  20 , the shape of the translucent lens  40 , and the like. A method for processing the gel sealant  30  into the prescribed shape involves executing gelling after the gel precursor of the gel sealant  30  is formed in the prescribed shape with a dispenser, screen printing, or the like. There also exists a method for forming the gel sealant  30  into the prescribed shape after gelling of the gel precursor, and the method is not particularly limited as long as the gel sealant  30  can be formed in the prescribed shape. 
     A method for processing the gel sealant  30  into the prescribed shape after gelling involves, as shown in  FIG. 2 , for example, spreading the gel precursor  35  of the gel sealant  30  into a film and executing gradual heating of the gel precursor  35  film, through a heating section such as a heater  39 , to form the gel sealant  30  film by moving the heater  39 . The thusly formed gel sealant  30  film is then die-cut or the like in the shape necessary to seal the LED element  10 . Therefore, the gel sealant  30  having the same shape as the base  20  or the translucent lens  40  can easily be formed. 
     During gelling, the gel precursor may be formed in the shape described above on a separating sheet, after which the gel precursor may then be gelled by heating and the formed gel sealant  30  may then be removed from the separating sheet. Therefore, when the formed gel sealant  30  is removed, the gel sealant  30  does not break and a portion thereof does not remain on the sheet. Furthermore, the gel sealant  30  can be removed from the separating sheet after being placed on the LED element  10  with the separating sheet still attached. Therefore, the gel sealant  30  can be placed on the LED element  10  without being damaged or dirtied. In other words, the gel sealant  30  can be easily handled. 
     Next, as shown in  FIG. 3 , the gel sealant  30  formed in the manner described above is placed on the LED element  10 , which is stored in the concave portion of the base  20  and connected to the lead wires  22  by the wires  11 . At this time the wires  11  may be coated with a resin or the like to prevent disconnection and to increase mechanical strength. Furthermore, the wires  11  may be laid along the concave portion of the base  20 . 
     After the gel sealant  30  is placed on the LED element  10 , the translucent lens  40  is placed on the gel sealant  30 . As shown in  FIG. 4 , the translucent lens  40  is then pressed toward the LED element  10  to sandwich the gel sealant  30  between the LED element  10  and the translucent lens  40 , thereby sealing the LED element  10  with the gel sealant  30 . The base  20 , the translucent lens  40 , the LED element  10 , and the gel sealant  30  are then unified to form the LED element module  1 . 
     The gel sealant  30  sealing the LED element  10  is caused to gel before being placed on the LED element  10 . Accordingly, even where the gel precursor using the solvent is used, the LED element  10  can be sealed without mixing in air bubbles caused by the solvent because the solvent is evaporated before the gel sealant  30  is placed on the LED element  10 . In other words, substance using solvent can be used as the gel precursor of the gel sealant  30 . 
     A method for pressing the translucent lens  40  toward the LED element  10  is not particularly limited. For example, as shown in  FIG. 5 , multiple as of yet unformed LED element modules are arranged in a condition where the translucent lens  40  is placed on the gel sealant  30 , and an area surrounding the elements is depressurized by a pump or the like. Each translucent lens  40  is then pressed from above each LED element  10  by a pressing section such as a bonder  2  having appropriate softness at a portion thereof contacting the translucent lens  40 . By depressurizing the surrounding area during pressing of the translucent lens  40 , gas trapped between the translucent lens  40  and the gel sealant  30 , between the gel sealant  30  and the LED element  10 , and the like can be reduced. In other words, the LED element  10  can be sealed by the gel sealant  30  without mixing in air bubbles that cause degradation of the light output or the like. Furthermore, pressing of the translucent lens  40  by the bonder  2  is not limited to an arrangement of multiple unformed LED element modules, and may be performed on a single unformed LED element module as well. The bonder  2  used here is not particularly limited as long as the bonder  2  is relatively soft, and may be, for example, rubber, gelled resin, or the like. 
     In the sealing method of the present invention, the gel sealant  30  may be pressed against the LED element  10  before the translucent lens  40  is placed on the gel sealant  30 . By this pressing, the air bubbles are pressed outward from between the LED element  10  and the gel sealant  30 , so that an amount of mixed in air bubbles is decreased. For example, in the method shown in  FIG. 6 , the gel sealant  30  may be pressed against the LED element  10 . 
     Such a process involves, as shown in  FIG. 6 , aligning a position of the gel sealant  30  formed in a shape on the separating sheet through the method described above with a position of the base storing the LED element  10  in a prescribed location detachably affixed to the film or the like at roughly the same interval as the gel sealant  30 . Therefore, the position of the gel sealant  30  can be aligned with the position of the LED element  10 . The gel sealants  30  and the LED elements  10  having aligned positions are held in place and moved on rollers  3  having a space therebetween to sufficiently press the gel sealant  30  against the LED element  10 . In other words, the gel sealants  30  and the LED elements  10  having aligned positions are sandwiched by the rollers  3  such that the gel sealant is continuously pressed from one end to the other end against the LED element  10 . By sandwiching the gel sealant  30  and the LED element  10  between the rollers  3 , the gel sealant  30  can be pressed against the LED element  10 . At the same time as the pressing, the gel sealant  30  can be removed from the separating sheet. Through such a method the air bubbles mixed in between the gel sealant  30  and the LED element  10  can be moved in a direction from one end of the gel sealant  30  to the other end and then pushed out externally. Accordingly, mixing in of the air bubbles between the gel sealant  30  and the LED element  10  can be prevented. In addition to the aforementioned method, other methods, such as moving the rollers to press the gel sealant  30  against the LED element  10 , for example, may be used. 
     After the gel sealant  30  has been pressed against the LED element through the aforementioned method, the translucent lens  40  can be placed on the gel sealant  30  and then pressed toward the LED element  10  to seal the LED element  10 , in the manner described above. Because the gel sealant  30  has lost fluidity, it is not necessary to subject the gel sealant  30  to the gelling process such as heating or the like after the LED element  10  is sealed. 
     The light emitting element module of the present invention can be formed according to the method for sealing the light emitting element as described above. Therefore, the mixing of air bubbles into the light emitting element module can be prevented, so that the light emitting element module does not have decreased light output caused by air bubbles. Furthermore, because the gel precursor including the solvent can be used, the refractive index of the gel sealant can be adjusted to match the refractive index of the translucent lens by arbitrarily changing the material of the gel sealant or the substance mixed into the sealant, so that the light emitting element module having increased brightness can be formed. 
     EXAMPLES 
     First Example 
     5 g of bis (4-methacryloyl-thiophenyl)sulfide (product of Sumitomo Seika Chemicals Co., Ltd.), 5 g of urethane acrylate EB230 (product of Daicel), and 0.1 g of polymeric initiator Perhexyl O (product of NOF corporation) were mixed into a mixed solution in which toluene and methyl ethyl ketone were mixed at a 1:1 ratio. A drop of the mixed solution, having a circular shape with a diameter of 3 mm and a thickness of 0.75 mm after the gel is formed, was then dripped onto the separating sheet using a dispenser. Thereafter, heat of 100 degrees Celsius was applied to the mixed solution to evaporate the solvent and cause the mixed solution to gel, thereby forming the gel sealant to be placed on the LED element. The refractive index of this gel sealant was 1.61. 
     The LED element was stored in the concave portion of the base, and the electrodes of the LED element were connected to the lead wires of the base by gold wires. The gel sealant formed in the first example was then grasped by tweezers and placed on the LED element  10 . The translucent lens was then placed on the gel sealant. The refractive index of the translucent lens was 1.61. Multiple as of yet unformed LED element modules, which were made up of the LED element, the gel sealant placed on the LED element, and the translucent lens placed on the gel sealant, were arranged in a space that can be depressurized. The area in which the as of yet unformed LED element modules were arranged was then depressurized to 0.5 Torr, after which the bonder formed of silicone rubber was used to press the translucent lens from above toward the LED element, thereby sealing the LED element. At this time, the pressure was set to 10000 Pa. 
     Through the aforementioned method, even where a solution is used in which the gel precursor of the gel sealant is dissolved in the solvent, the LED element can be sealed by the gel sealant without mixing in air bubbles. Furthermore, through the aforementioned method, the LED element module can be formed without air bubbles. Yet further, the refractive index of the translucent lens and the refractive index of the gel sealant can be made substantially the same, thereby increasing the brightness of the formed LED element module. 
     Second Example 
     A dispersion liquid, containing 4 g of oxidized titanium nanoparticles having an average particle diameter of 12 nm dispersed in a methyl ethyl ketone, was mixed with 10 g of silicone 3062 A liquid (product of GE Toshiba Silicone Co., Ltd.) used for potting. Next, a mixture formed in the same manner by mixing 10 g of silicone 3062 B liquid (product of GE Toshiba Silicone Co., Ltd.) used for potting into the A liquid having the dispersion liquid mixed therein was stretched to coat the separating sheet to form a film having a thickness of 1.25 mm. Heat of 150 degrees Celsius was applied by a heater to the mixture stretched into a film to evaporate the solvent and harden the mixture, thereby forming the gel film. 
     The LED element was stored in the concave portion of the base, and the electrodes of the LED element were connected to the lead wires of the base by gold wires. The multiple bases storing the LED elements  10  were then detachably affixed to a base film at prescribed intervals. 
     Next, the formed gel film was die-cut, without cutting the separating sheet, in accordance with the intervals of the multiple bases, affixed to the base film, storing the LED elements. At this time, the gel film was die-cut to form the gel sealant having the diameter of 4 mm and the thickness of 1.25 mm. 
     The position of the bases storing the LED elements on the base film was aligned with the position of the gel sealant formed on the separating sheet, and the roller pushed the gel sealant onto the base to laminate the base and gel sealant while the base film and the separating sheet were moved from one end of the gel sealant to the other end thereof. In other words, the gel sealant and the LED element was moved from one end of the gel sealant to the other end thereof while the gel sealant was pressed against the LED element, thereby preventing the mixing in of air bubbles between the gel sealant and the LED element. 
     After the pressing, the separating sheet was removed, the translucent lens was placed on the gel sealant, and the LED element was sealed by the gel sealant through the method according to the first example. Therefore, even where a solution is used in which the gel precursor of the gel sealant is dissolved in the solvent, the LED element can be sealed by the gel sealant without mixing in air bubbles. Furthermore, through the aforementioned method, the LED element module can be formed without air bubbles. 
     Third Example 
     Instead of the dispersion liquid of oxidized titanium nanoparticles dispersed in methyl ethyl ketone and mixed with the liquid A as shown in the second example, only the methyl ethyl ketone, serving as the solvent, was mixed with the liquid A to form the silicone gel, and the LED element was then sealed in the same manner as described in the second example. Therefore, even where a solution is used in which the gel precursor of the gel sealant is dissolved in the solvent, the LED element can be sealed by the gel sealant without mixing in air bubbles. Furthermore, through the aforementioned method, the LED element module can be formed without air bubbles. 
     Fourth Example 
     The viscoelastic measurement was executed using a dynamic viscoelastic measurement device (DMS-6100 (product of SII NanoTechnology Inc.)). The gel sealants formed in the first example and the third example were measured in a manner such that the resin compound having a diameter of 12.5 mm was sandwiched between parallel plates, the bottom plate was moved alternately left and right under a strain of 10%, an angular speed was changed within a range of 0.1 rad/s to 400 rad/s, and the storage elastic modulus (G′), the loss elastic modulus (G″), and the tan δ were measured. A result of the measurement was that the gel sealant formed according to the first example has a storage elastic modulus (G′) of 0.12 MPa, a loss elastic modulus (G″) of 1.5 kPa, and a tan δ of 0.0125, which is less than or equal to 1. The gel sealant formed according to the third example has a storage elastic modulus (G′) of 17 kPa, a loss elastic modulus (G″) of 750 Pa, and a tan δ of 0.0441, which is less than or equal to 1. Therefore, it is understood the gel sealants formed according to the first example and the third example has no fluidity. 
     It should be understood that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the present invention and without diminishing its intended advantages. It is therefore intended that such changes and modifications be covered by the appended claims.