Abstract:
A light emitting device is provided that can effectively dissipate heat generated by high power operation and has superior workability in mounting and less positional displacement. The light emitting device includes a planar base substrate made of a metal, a package member bonded to a main surface side of the base substrate, and an insulating member and a conductive member which are provided at least partially between the base substrate and the package member, wherein the package member has opening portions where the insulating member and the conductive member are exposed at bottom parts thereof, and the opening portions include a first opening portion in which a light emitting element is mounted and a second opening portion located separate from the first opening portion and also opening from a side surface of the package member.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a light emitting device and a lighting device using a semiconductor light emitting element. 
   2. Description of the Related Art 
   There has been a line light source and the like employing a light emitting device, which comprises a discharge tube such as a fluorescent lamp or a semiconductor light emitting element, as a lighting device of a document reader in an information processor such as a facsimile, copier, and image scanner. In recent years, downsizing of devices have been carried forward and a line light source using semiconductor light emitting elements has become mainstream. Such line light sources include a direct lighting type in which a plurality of light emitting devices are arranged in line so that light from each of the light emitting devices is projected directly onto a document etc. and a light guide type in which one or more light emitting devices are arranged at an end portion of a transparent light guide having a bar shape or a plate shape so as to introduce light thereto and then the light is projected onto a document etc. from the light guide (for example, see Japanese Laid-open Patent Application Nos. 2003-23525 and 2005-217644). 
   A conventional lighting device using a light guide is shown in  FIG. 4 . In a lighting device  500 , a light emitting device  400  is arranged at an end surface of a light guide  412  so as to introduce light from the light emitting device to the end surface of the light guide  412 . The light guide  412  is set to a white light guide casing  411  such that the emitting surface of the light guide  412  is exposed. Incident light to the light guide  412  is transmitted through the light guide  412  in the longitudinal direction while reflected by the inner surfaces thereof. Then, light is emitted from the emitting surface of the light guide  412  provided along the longitudinal direction so that light can be projected to a document etc. As described above, light is projected not as a point light source but as a surface light source, and thus, the lighting device  500  can emit uniform light. While the direct lighting type described above needs to mount the light emitting devices densely in order to reduce nonuniform emission, the light guide type using a light guide has an advantage in which nonuniform emission can be reduced even with fewer light sources (light emitting devices). Moreover, because the lighting device using a light guide has a simple structure in which a light emitting device is arranged only at the end surface of the light guide, it has an advantage that a complex circuit is not needed and the lighting device can be made thin. 
   In the light emitting device used in the lighting device described above, as shown in  FIG. 3 , an opening portion  300 A for mounting a light emitting device is provided in a resin package  301  which is provided with a plurality of lead frames  310 . The lead frames  310  protrude from a side surface of the package  301  as external connecting terminals. Then, the lead frames  310  are engaged with the circuit substrate of the lighting device and electrically connected thereto so that light can be emitted. The through holes  300 D are used for fixing the light emitting device to the light guide casing when assembling a line lighting device. 
   In the information processors, while downsizing, various performance thereof have been improved year after year, and further improvements in performance have been required. For example, improvements in characteristics such as multifunctionality and operationality enable various processings and also allow users to make effective use, so that the range of usage has been expanding. Also, enhancement of processing capability, that is, capability of high-speed processing is one of the important characteristics. For high-speed processing, high-speed reading of images is necessary. There are several effective ways to achieve this, and among them, increasing the brightness of light illuminating the reading surface of a document is effective, and processing time can be reduced by increasing the quantity of light for reading data. 
   The amount of light can be increased by increasing the number of light emitting devices that are used as the light source. That is, in the above-described direct lighting type in which a plurality of light emitting devices are arranged in line, it can be achieved by densely mounting the light emitting devices. However, in this case, the size of the lighting device becomes larger so that the image reading device inevitably becomes larger. Moreover, there are negative effects in which the densely mounted light emitting devices produce a large amount of heat, the power consumption is also increased, and deterioration of various electronic components is accelerated, and therefore, it is undesirable to densely mount the light emitting devices. 
   In the light guide type in which the light emitting devices are mounted at an end surface of the light guide, the area of the end surface is limited. In this case, high power output can be realized by increasing the number of the light emitting elements incorporated in a light emitting device. However, this case is similar to the case described above in that a plurality of light emitting elements, which generate heat, are used. Therefore, problems caused by the generated heat from the light emitting elements occur. 
   To solve the problems caused by heat generation, in aforementioned Japanese Laid-open Patent Application No. 2003-23525, a material having high heat conductivity is used for the lead frame and thereby improving heat dissipation. In Japanese Laid-open Patent Application No. 2005-217644, heat dissipation is improved by providing an extended portion to the lead frame. 
   However, even if a material having high heat conductivity is used as described above, a portion of lead frame which is used as a pathway for heat dissipation is narrowed, so that it is difficult to dissipate heat. Therefore, sufficient heat dissipation cannot be obtained. 
   Also, mounting the light emitting device to the lighting device may be difficult because a plurality of lead frames protrude from the light emitting device. That is, in mounting, the lead frames are inserted in corresponding holes provided in the circuit and the like. Thus, workability may deteriorate when the number of the lead frames increases. In another case, the light emitting device inclines and that may cause deviation of the distance and degree between the light emitting device and the end surface of the light guide from desirable values. If this occurs, output from the light guide decreases. In addition, a part of the exposed lead frame may be bent during the manufacturing process etc., which makes inserting the lead frame into the corresponding hole more difficult. 
   Accordingly, the present invention is devised to provide a light emitting device capable of effectively dissipating heat generated by high power operation and has superior workability in mounting and less positional displacement. 
   SUMMARY OF THE INVENTION 
   To achieve the object described above, a light emitting device according to the present invention comprises a planar base substrate made of a metal, a package member bonded to a main surface side of the substrate, and an insulating member and a conductive member which are provided at least partially between the base substrate and the package member, wherein the package member has opening portions where the insulating member and the conductive member are exposed at bottom parts thereof, and the opening portions include a first opening portion in which a light emitting element is mounted and a second opening portion located separate from the first opening portion and also opens to a side surface of the package member. With this configuration, heat generated from a semiconductor element can be dissipated quickly to outside through the metallic base substrate, so that degradation due to heat can be prevented. Because the conductive member does not protrude to outside, mounting can be carried out without bending or damaging the conductive member and workability can be improved. Also, because a smaller region of the conductive member is exposed to outside, deterioration thereof can be controlled. 
   Moreover, a part of the base substrate preferably penetrates the insulating member and is exposed at the bottom part of one of the first and second opening portions. With this construction, heat from the light emitting element can be more efficiently dissipated to outside. 
   The package member preferably has a third opening portion in which the protective element is mounted. With this construction, a light emitting device having excellent electrostatic breakdown strength can be obtained. 
   Also, a lighting device of the present invention comprises a light emitting device, a light guide introducing emission from the first opening portion from an end surface and an external electrode connected with a conductive member exposed at a bottom part of the second opening portion. With this construction, a lead frame can be electrically bonded without protruding from the light emitting device. Also, because the package member is not provided on the rear surface of the light emitting device, the thickness of the light emitting device when it is laced at an end surface of the light guide member can be further reduced, so that downsizing of the lighting device can be achieved. 
   In the light emitting device and lighting device according to the present invention, heat can be transferred effectively from the light emitting element to outside, therefore, a light emitting device and lighting device with excellent lifetime performance can be obtained without lowering the light emitting efficiency. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1A  is a front elevational view of a light emitting device according to one embodiment of the present invention. 
       FIG. 1B  is a schematic perspective view of the light emitting device illustrated in  FIG. 1A . 
       FIG. 1C  is a partially enlarged view of the light emitting device illustrated in  FIG. 1A . 
       FIG. 1D  is a partial cross sectional view of the light emitting device taken along a section line X-X′ of  FIG. 1C . 
       FIG. 1E  is a partially enlarged view of  FIG. 2A . 
       FIG. 2A  is a front elevational view of a modified light emitting device according to the embodiment of the present invention. 
       FIG. 2B  is a partially enlarged view of the light emitting device illustrated in  FIG. 2A . 
       FIG. 3  is a front elevational view showing a conventional light emitting device. 
       FIG. 4  is a perspective view illustrating a lighting device using a conventional light emitting device. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. Herein, the forms of the following embodiments are intended as examples of a light emitting device and a lighting device according to the present invention. Thus, the following descriptions of the embodiments according to the present invention are provided for illustration only, and not for the purpose of limiting the invention as defined by the appended claims and their equivalents. 
   In addition, the present specification will by no means limit the members described in claims to the members described in the embodiments. Unless otherwise specified, the dimensions, materials, shapes, relative layouts and so fourth of the constituent members described in the preferred embodiments are for illustration only, and do not intend to limit the invention therein. The sizes, positional relationships, and so forth of the members shown in the drawings may be exaggerated in order to clarify the description. Furthermore, in the description below, identical members or members of the same quality are assigned the same names and reference numerals and detailed description thereof will be arbitrarily omitted. In addition, the elements that make up the present invention may be such that a plurality of elements are constituted by a single member so that a single member can serve as multiple elements, or conversely, function of a single element may be shared by a plurality of members. The light emitting device and the lighting device according to the present embodiment will be described below with reference to the accompanying drawings. 
     FIG. 1  shows a light emitting device  100  of the present embodiment.  FIG. 1A  is an elevational view from the front and  FIG. 1B  is a perspective view.  FIG. 1C  is an enlarged view of a first opening portion  100 A and  FIG. 1D  is a cross-sectional view taken along a section line X-X′ of  FIG. 1C .  FIG. 1E  is an enlarged view of a second opening portion  100 B. 
   In  FIGS. 1A and 1B , a package member  101  is bonded to one surface of a planar base substrate  102  made of metal. An insulating member  104  and a plurality of conductive members  103   a ,  103   b ,  103   c , and  103   d  are provided between the base substrate  102  and the package member  101 . Further, the first opening portion  100 A and the second opening portions  100 B 1  and  100 B 2 , in which the insulating member and the conductive members are exposed at the bottom surfaces thereof, are formed. In other words, the first opening portion  100 A and the second opening portions  100 B 1  and  100 B 2  are formed in the package member  101  so that the base substrate  102  and/or the conductive members  103   a  to  103   d  are not covered by the package member  101  at the first opening portion  100 A and the second opening portions  100 B 1  and  100 B 2 . The second opening portions  100 B 1  and  100 B 2  also open to a side surface of the package member  101 . The conductive materials  103   a  to  103   d  extend continuously from the first opening portion  100 A to the second opening portions  100 B 1  and  100 B 2 , and connected to external electrodes at the second opening portions  100 B 1  and  100 B 2  so that current can be supplied to light emitting elements  105   a  to  105   c.    
   Each constituent of the light emitting device  100  of the present invention will now be described below. 
   (Base Substrate) 
   In the present invention, the base substrate  102  is made of metal, and especially, a metal having good thermal conductivity is preferably used. Specific examples of such materials include, but not limited to, copper (thermal conductivity of 390 W/m·K), iron (thermal conductivity of 84 W/m·K), aluminum (thermal conductivity of 236 W/m·K), and the like, and copper and aluminum are preferable. Such metals can be used not only singly but also as an alloy. Such metals may be multi-layered. The thickness of the base substrate  102  can be arbitrarily set according to the size and so forth of the light emitting device  100 . 
   The shape of the base substrate  102  is preferably generally planar, and a metal plate having a desired thickness and so forth can be used as the base substrate  102 . A generally planar structure can be easily processed, so that the package member  101  can be easily bonded to the base substrate  102  in a manufacturing process. However, it is acceptable to apply a process such as forming fine irregularity on the surface of the base substrate  102 . In other words, smoothness of the surface is not specifically limited to be perfectly flat as long as the surface of the base substrate  102  is generally planar. Heat is released to outside from the surface (rear surface) of the base substrate  102  to which the package member  101  or the like is not bonded. Therefore, by applying a processing such as forming irregularity to the surface of the base substrate  102  to increase the surface area, the light emitting device  100  with further excellent heat dissipation can be obtained. 
   The shape viewed from the front surface side of the base substrate  102  (the side on which the package member  101  is provided) is preferably substantially rectangular, and the specific shape of the base substrate  102  can be arbitrarily selected according to purpose and usage of the light emitting device  100 . For example, the shape may be a horizontally long rectangle as shown in  FIG. 1A , or a vertically long rectangle as shown in  FIG. 2 .  FIG. 2  shows a modified light emitting device  200  in accordance with the present invention. 
   As described above, the base substrate  102  is preferably generally planar, but a protruding portion or portions may be provided on the base substrate  102 . For example, as shown in  FIG. 1D , at the bottom surface of the first opening portion  100 A (i.e., the portion of the base substrate  102  corresponding to the first opening portion  100 A of the package member  101 ), a part of the base substrate  102  may have a protruding portion  102 A which penetrates through the insulating member  104  and is exposed at the bottom surface of the first opening portion  100 A. When the light emitting element  105   b  is mounted on the upper surface of the protruding portion  102 A, heat generated from the light emitting element  105   b  is directly transferred to the base substrate  102 , so that efficient heat dissipation can be obtained. Especially, when a gallium nitride based semiconductor is used as the light emitting element  105   b , the amount of generated heat is greater than the amount of generated heat when a gallium arsenide based semiconductor etc. is used. Therefore, by bonding the light emitting element  105   b  directly to the base substrate  102 , heat dissipation can be improved and deterioration of the light emitting element  105   b  can be prevented. 
   Furthermore, a through hole can be formed in the light emitting device. The light emitting device of the present invention may be mounted in a lighting device (e.g., a lighting device including the light guide  412  and the light guide case  411  as shown in  FIG. 4 ) and, with a light guide and other components of the lighting device, incorporated into an information processor such as a printer and the like. In such case, the through hole formed in the light emitting device can be used for position adjustment or the like. For example, as the through holes  200 D shown in  FIG. 2  and the like, the through hole openings that penetrate through the base substrate and the package member may be provided in regions that would not affect the operations and characteristics of the light emitting device either optically or electrically. Then, the base substrate can be fitted with a light guide and other components of the lighting device, so that positioning and fixing can be carried out easier. 
   (Package Member) 
   In the present invention, the package member  101  of the light emitting device  100  has at least the first opening portion  100 A formed in a position corresponding to a portion of the base substrate  102  in which the light emitting elements  15   b  are mounted. The package member  101  further includes the second opening portions  100 B 1  and  100 B 2  which are spaced from the first opening portion  100 A and also open to a side surface of the package member  101 . The conductive members  103   a  to  103   d  which extend from the first opening portion  100 A are exposed at the bottom surface of the second opening portions  100 B 1  and  100 B 2  in order to establish an electric connection with the external electrodes (not shown). The insulating member  104  and the conductive members  103   a  to  103   d  are interposed at least a part between the package member  101  and the substrate  102 . The substrate  102  and the package member  101  may be bonded by a bonding member such as an epoxy resin, a conductive adhesive material, an adhesive sheet, and the like. 
   The package member  101  preferably has a shape generally planar, in a similar way as the base substrate  102 . When viewed from the front, the outermost shape of the package member  101  is preferably substantially the same as that of the base substrate  102 . For example, as shown in  FIG. 1A  and  FIG. 2A , a rectangular shape of the package member  101  is preferable in conformity with the rectangular base substrate  102 . In this case, the substrate  102  and the package  101  can be made substantially the same size by, for example in a post-process, after bonding the package member  101  on the substrate  102 , carrying out cutting at desired positions to obtain the individual light emitting device. However, it is not limited thereto and the size of the substrate  102  and the package member  101  may be different. Furthermore, it is necessary to arrange the substrate  102  so as to be able to form the bottom surfaces where the conductive members  103   a  to  103   d  are exposed, in the regions for the first opening portion  100 A and the second opening portions  100 B 1  and  100 B 2 . 
   As the material for the package member  101 , an insulating member or a member which does not transmit light from the light emitting elements  105   a  to  105   c  and external light easily are preferable. In addition, a material having a certain degree of strength is preferable to be used as the material for the package member  101 . Specific examples of the materials include, but not limited to, phenol resins, glass epoxy resins, BT resins, ceramics (aluminum nitride and alumina), and PPA. The package member  101  may be obtained by forming such materials in generally planar shape and bonding to the base substrate  102  with an above-mentioned adhesive member and the like. 
   (First Opening Portion) 
   In the first opening portion  100 A, the conductive members  103   a  to  103   d  are exposed at the bottom surface so as to electrically connect the conductive members  103   a  to  103   d  with the light emitting elements  105   a  to  105   c . The location for forming the first opening portion  100 A is arranged in  FIG. 1A  at a generally center portion in the longitudinal direction; and in the shorter direction, at a position with a longer distance from the side surface where the second opening portions  100 B 1  and  100 B 2  are formed (i.e., a position closer to the side surface where the second opening portions  100 B 1  and  100 B 2  are not formed than the side surface where the second opening portions  100 B 1  and  100 B 2  are formed). However, the arrangement of the first opening portion  100 A is not limited thereto and suitably designed according to the shape or the like of the lighting device in which the light emitting device  100  is incorporated, and other components. For example, the first opening portion  100 A may be arranged at a position offset from the center in the longitudinal direction. 
   As the shape of the opening of the first opening portion  100 A, a rectangle with rounded corners is shown in  FIG. 1A  as an example, but the shape is not limited thereto. For example, the shape of the opening may be square, circular, oval, diamond, or trapezoidal. Also, the number of the first opening portion  100 A is not limited to one as shown in  FIG. 1A , but a plurality of the first opening portions  100 A may be provided in the package member  101 . In addition, a shape which is a combination of various shapes can be employed. For example, a shape formed by connecting two openings of circular opening portions can be employed. Also, in the case where the shape of the first opening portions  100 A is generally rectangular as shown in  FIG. 1A , a side surface of the package member  101  and the side surface of first the opening portion  100 A may be arranged substantially in parallel (as shown in  FIG. 1A ) or at an angle. 
   The side surface of the first opening portion  100 A is illustrated as being substantially perpendicular to the bottom surface in  FIG. 1D . However, the shape or angle of the side surface of the first opening portion  100 A is not limited thereto, and the side surface may be inclined. In this instance, light irradiated to the side surface can be reflected in the opening direction by inclining the side surface toward the opening direction of the first opening portion  100 A, so that light extraction efficiency can be improved. 
   The light emitting elements  105   a  to  105   c  provided in the first opening portion  100 A may be mounted on one or more of the conductive members  103   a  to  103   d , the insulating member  104 , or the protruding portions  102 A of the base substrate  102  as described above, or may be mounted via another member such as a submount. As the light emitting elements  105   a  to  105   c , semiconductor light emitting elements capable of respectively emitting light of blue, green, and red, are used. The size and number etc. of the light emitting elements  105   a  to  105   c  can be arbitrarily selected. For example, as shown in  FIG. 1 , a blue light emitting element, a green light emitting element and three red light emitting elements may be mounted. Therefore, the first opening portion  100 A is needed to have an area for mounting the light emitting elements  105   a  to  105   c  and a size that is capable of exposing the conductive members  103   a  to  103   d  for establishing an electrical connection and also is capable of wire bonding. 
   The light emitting elements  105   a  to  105   c  or the like is arranged in the first opening portion  100 A, therefore, the first opening portion  100 A is preferably filled with a sealing member to cover them. For example, as shown in  FIG. 1D , an insulating member  106 , which covers the light emitting elements  105   a  to  105   c  (only the light emitting element  105   b  is shown in  FIG. 1D ) and the conductive wires  107 , is filled in the first opening portion  100 A. The insulating member  106  is adjusted to approximately the same height as the upper surface of the package member  101  defining the first opening portion  100 A. As the sealing member, a light transmitting resin capable of transmitting light from the light emitting elements  105   a  to  105   c  is preferable, specifically, a rein having excellent weather resistance, such as an epoxy resin, a silicone resin, an urea resin, and a polyamide, is preferable. Especially, a silicone resin is preferable because it also has excellent thermal resistance. The sealing member may include a diffusion member capable of diffusing light from the light emitting elements  105   a  to  105   c , and a color converting member such as a fluorescent material which absorbs light from the light emitting element and convert to light having a different wavelength than that of the light from the light emitting elements  105   a  to  105   c.    
   (Second Opening Portion) 
   The second opening portions  100 B 1  and  100 B 2  open, in the same manner as in the first opening portion  100 A, to the upper surface of the package member  101 , and further, to the side surface of the light emitting device  100  (side surface of the package member  101 ). In the bottom surface or the bottom portion in the second opening portions  100 B 1  and  100 B 2 , the conductive members  103   a  to  103   d  continuous from the first opening portion  100 A is exposed for establishing an electrical connection with the external electrodes (not shown). The second opening portions  100 B 1  and  100 B 2  are arranged to expose the conductive members  103   a  to  103   d  at the side surface of the package member  101 , which allows the structure to be easily mounted when the light emitting device is incorporated in the lighting device. Also, the lead frame does not protrude from the side surface etc. of the package member  101 , so that damage does not occur easily. 
   Further, most part of the conductive members  103   a  to  103   d  is enclosed between the package member  101  and the base substrate  102 , so that only the portions of the conductive members  103   a  to  103   d  at the bottom portions of the second opening portions  100 B 1  and  100 B 2  are exposed. Therefore, the conductive members  103   a  to  103   d  can be prevented from accidentally touching the other members or the like and receiving electric stress, and also from being deteriorated due to oxidation, discoloring, or the like. 
   The shape of the second opening portions  100 B 1  and  100 B 2  is preferably a shape in which, as shown in  FIG. 1 , a generally rectangular bottom surface is exposed, but it is not limited thereto. In a similar manner as the first opening portion  100 A, the shape of the second opening portions  100 B 1  and  100 B 2  may be square, circle, oval, diamond, trapezoid, and the like, which is arbitrarily selected according to the shape of the external electrodes or the like. 
   In addition, one or more of the second opening portions may be formed. For example, in  FIG. 1 , two second opening portions  100 B 1  and  100 B 2  are provided, in which the conductive members  103   a  and  103   b  are arranged so as to be exposed in the second opening portion  100 B 1  and the conductive members  103   c  and  103   d  are arranged so as to be exposed in the second opening portion  100 B 2 . As described above, by providing a plurality of second opening portions, positioning of the light emitting device  100  with other members can be facilitated. The anodes and cathodes may be respectively exposed at the different second openings, or a second opening portion may be provided for each conductive member. 
   The conductive members  103   a  to  103   d  exposed at the bottom surface of the second opening portions  100 B 1  and  100 B 2  may be covered with a protective member except for an area which is connected to the external electrodes. For example, as shown in  FIG. 1E , a protective member  108  can be arranged along a side wall of the second opening portion  100 B 1  so that the center portion of the conductive members  103   a  and  103   b  are exposed without being covered with the protective member  108 . With this configuration, the area of the conductive members  103   a  and  103   b  exposed to ambient air can be limited to an area necessary for electrical connection, so that degradation and the like can be prevented. As the protective member, an insulating member is preferable, and specifically, a thermosetting resin such as an epoxy resin is preferable. 
   (Insulating Member) 
   The insulating member  104  is interposed to insulate the conductive members  103   a  to  103   d  arranged on the insulating member  104  and the metal base substrate  102 . Therefore, the insulating member  104  is not necessarily provided on the area where the conductive members  103   a  to  103   d  are not arranged. As the material of the insulating member  104 , thermosetting resins such as epoxy resins are preferable and provided on the base substrate  102  by way of printing, attaching, coating or the like. These materials may be used singly or in combination of two or more kinds. When two or more kinds of materials are used to form the insulating member  104 , they may be stacked or mixed. 
   A thickness sufficient to maintain the insulation is needed for the insulating member  104  and a thickness of at least 5 μm is preferable, and a thickness between 15 μm to 30 μm is more preferable. Also, in view of thermal expansion coefficient etc. of the package member  101  and the base substrate  102 , a filler may be mixed into the insulating member  104 . 
   (Conductive Member) 
   The conductive members  103   a  to  103   d  are provided electrically continuously from the first opening portion  100 A to one of the second opening portion  100 B 1  or  100 B 2 , for electrically connecting with the light emitting elements  105   a  to  105   c , a protective element, and the like. As the material of the conductive members  103   a  to  103   d , copper, tungsten, molybdenum and the like, having excellent conductivity are preferable, and specifically, copper is preferable. The conductive members  103   a  to  103   d  need to have a sufficient thickness which does not cause an excessive electric resistance. The thickness of the conductive members  103   a  to  103   d  is preferably about 10 to 50 μm, more preferably about 15 to 40 μm. The conductive members  103   a  to  103   d  are disposed so that an area necessary for establishing an electric connection is at least exposed in the first opening portions  100 A. The light emitting elements  105   a  to  105   c  are preferably mounted individually so that each of the light emitting elements  105   a  to  105   c  functions independently. 
   (Light Emitting Element) 
   The light emitting elements  105   a  to  105   c  of the present invention comprises a semiconductor light emitting element and is capable of emitting at least visible light. For color scanner or the like, light emitting elements capable of emitting at least three primary colors of light (i.e., red, blue, and green) are preferably used. Specifically, for constructing blue and green light emitting elements, ZnSe and nitride semiconductor (In X Al Y Ga 1-X-Y N, 0≦X, 0≦Y, X+Y≦1) may be used. For constructing red light emitting elements, GaAs, InP, and the like may be used. Moreover, light emitting elements comprising materials other than that described above may be used. Also, light emitting elements capable of emitting light other than three primary colors of light may also be used. Composition, emitting color, size, and number of the light emitting elements can be selected arbitrarily according to purpose. These light emitting elements  105   a  to  105   c  are arranged in the first opening portion  100 A. In the case where the light emitting elements  105   a  to  105   c  comprise a semiconductor layer grown on an insulating substrate, such as a light emitting element comprising a nitride semiconductor layer grown on a sapphire substrate, and the substrate side is the mounting surface, one or more of the light emitting elements  105   a  to  105   c  may be mounted either on the insulating member  104  at the bottom surface of the first opening portion  100 A or on the conductive members  103   a  to  103   d . Also, as described above and shown in  FIG. 1D , the light emitting elements  105   a  to  105   c  may be mounted on the protruding portion  102 A of the base substrate  102 . With this configuration, heat generated from the light emitting elements  105   a  to  105   c  can be transferred very efficiently to the base substrate  102 , so that excellent heat dissipation can be obtained. The conductive members  103   a  to  103   d  and the light emitting elements  105   a  to  105   c  can be electrically connected by connecting the electrode provided on the light emitting elements  105   a  to  105   c  and the conductive members  103   a  to  103   d  using a wire (such as the wire  107  shown in  FIG. 1D ) made of gold, and the like. In the case where not the insulating substrate side but the semiconductor layer side which is grown on the insulating substrate is the mounting surface, that is, when the electrode disposed on the semiconductor layer is bonded to a conductive member by using an adhering member, the light emitting elements  105   a  to  105   c  may be mounted on the corresponding conductive members  103   a  to  103   d.    
   In the case where the light emitting elements  105   a  to  105   c  is a semiconductor layer grown on a conductive substrate, for example, a light emitting element made of a nitride semiconductor layer grown on a SiC substrate or a light emitting element made of a GaAs semiconductor layer grown on a GaAs substrate, electrical connection is needed to be established through the back surface of the light emitting elements  105   a  to  105   c . Therefore, the light emitting elements  105   a  to  105   c  are preferably mounted on the corresponding conductive members  103   a  to  103   d  which are exposed at the bottom surface of the first opening portion  100 A. In this case, an adhering member of conductive material is used. 
   The mounting position of each color of the light emitting elements  105   a  to  105   c  is not specifically limited and arbitrarily selected in view of the mounting position of the conductive members  103   a  to  103   d  and optical characteristics or the like. The light emitting elements  105   a  to  105   c  can also be mounted at the bottom surface of the first opening portion  100 A via a submount etc. 
   (Third Opening Portion) 
   In addition to a semiconductor light emitting element (e.g., the light emitting elements  105   a  to  105   c ), a semiconductor photodetector, and further, a protective element (e.g. a Zener diode and a condenser) that protects such semiconductor elements from damage caused by overvoltage, or combination of two or more thereof may be mounted in the light emitting device. In this case, it is preferable to provide a third opening portion separately from the first and second opening portions so as to mount the additional element therein. For example, as shown in  FIGS. 2A and 2B , a third opening portion  200 C is provided at a position spaced from the first opening portion  200 A. The protective elements  209  are mounted in the third opening portion  200 C and electrically connected by using wires or the like, then, covered with a sealing member and the like. The conductive member exposed at the third opening portion  200 C is continuously provided so that the conductive member is also exposed at the first and second opening portions  200 A and  200 B. For the sealing member herein, a similar member (e.g., the sealing member  106  illustrated in  FIG. 1D ) as described above applied to the first opening portion  100 A can be used. Further, the sealing member in the third opening portion  200 C does not have to be light transmissive, so that an opaque member can be used. 
   The light emitting device shown in  FIG. 2A  comprises a plurality of through holes  200 D in addition to the first to third opening portions  200 A to  200 C. The through holes  200 D pass through from the upper surface of the package member  201  to the rear surface of the base substrate, and thus, position adjustment can be easily realized. Single or multiple through holes can be provided in a region where the electric conduction is not affected. For example, as shown in  FIG. 2A , the through holes  200 D may be provided at four positions. Size and shape of the through holes  200 D can also be arbitrarily selected, for instance, as shown in  FIG. 2A , two sets of columnar through holes  200 D with different diameters are provided. Such through holes  200 D are more effective as the size of the light emitting device increases. Especially, when the light emitting device is used in application likely associated with vibration or shock, adversely affect on optical characteristics can be avoided while maintaining electric conductivity. 
   (Lighting Device) 
   In the lighting device of the present invention, a light emitting device is arranged at an end surface of a light guide (such as the light guide  412  illustrated in  FIG. 4 ) having a bar shape or a plate shape and, for example, the lighting device may be designed as such device used for a line lighting in a scanner or other information processor. Specifically, a light guide is housed in a light guide case (such as the light guide case  411  illustrated in  FIG. 4 ) so as to expose the emission surface, and the light emitting device (e.g., the light emitting device  100  or  200 ) is arranged at an end surface of the light guide case so as to introduce incident light. Especially, in the present invention, the first opening portion (e.g., the first opening portion  100 A or  200 A) in which the light emitting element is arranged and the end surface of the light guide are arranged in face-to-face relation. Examples of the material for the light guide include light transmitting members such as glass and acrylic resin. In order to make uniform line light source, a light scattering pattern may be formed on the surface of the light guide by applying embossing treatment or light-scattering material or the like. 
   In addition to the light guide for transmitting light, the external electrodes are provided in the lighting device. The conducting portions of the external electrodes and the conductive members (e.g., the conducting members  103   a  to  103   d ) exposed at the bottom surface of the second opening portions (e.g., the second opening portions  100 B or  200 B) of the light emitting device are electrically connected. The connection between the external electrodes and the conductive members can be established by using a conductive wire etc. which is bonded with a bonding material such as a solder, or an electric bonding may be established by using an external electrode having a shape which fits with the second opening portions without using a bonding material. For example, the external electrodes are formed with shapes that fit to the second opening portions of the light emitting device, and a conductive portion may be provided on the surface of the external electrode corresponding to the conductive member of the second opening portion. With this arrangement, positioning can be achieved only by fitting them together and the electrical connection can also be established. With the construction described above, the light emitting device can be detached easily. 
   INDUSTRIAL APPLICABILITY 
   The light emitting device of the present invention can be utilized not only for lighting device used in an image reading apparatus such as a facsimile, copier machine, image scanner, but also for an indoor lighting apparatus, industrial lighting apparatus or the like. 
   It is to be understood that although the present invention has been described with regard to preferred embodiments thereof, various other embodiments and variants may occur to those skilled in the art, which are within the scope and spirit of the invention, and such other embodiments and variants are intended to be covered by the following claims. 
   This application is based on Japanese Patent Application No. 2006-128144 filed in Japan on May 2, 2006, the contents of which are incorporated hereinto by reference.