JP2004079750A - Light emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the occurrence of luminance unevenness and illumination unevenness in a light emitting device constituted by bonding a light reflecting case provided with a reflection mirror to the surface of a substrate on which a light emitting diode is fixed by aligning the light reflecting case with the substrate with high accuracy. <P>SOLUTION: Light emitting diodes 12 are fixed on an aluminum substrate 11 on which p-side lead-out wiring 15, n-side lead-out wiring 16, and alignment marks 19 are provided. Then the light reflecting case 25 provided with a silicon substrate 21 through which first holes 22 having reflection mirrors composed of aluminum films 20 on their side faces and second holes 23 for visually confirming the alignment marks 19 and a glass plate 24 coated with a nonreflective coating is bonded with solder to the surface of the aluminum substrate 11 by aligning the second holes 23 of the silicon substrate 21 with the alignment marks 19 of the substrate 11. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a light emitting device in which a plurality of light emitting elements are arranged two-dimensionally.
[0002]
[Prior art]
A light emitting diode is used as a light source for a display device or a printer arranged two-dimensionally because of its large contrast and viewing angle and long life. For example, at least first to third thermosensitive coloring layers having different colors to be developed are laminated, and the lower thermosensitive coloring layer has a lower thermosensitivity, and the uppermost first thermosensitive coloring layer on the surface side and the lower layer. For the second heat-sensitive color developing layer, there is a color heat-sensitive printer using a color heat-sensitive recording paper to which fixing property by ultraviolet rays in a specific wavelength range is imparted so that a full-color print can be obtained. In this color thermal printer, while the color thermal recording paper is reciprocally conveyed, the thermal head is pressed against each other to perform thermal recording on each thermal coloring layer, and after the thermal recording on each thermal coloring layer, the light emitting diodes are arranged in a matrix. The light emitting device provided is irradiated with ultraviolet rays using a fixing device that is used as a light source, and is fixed so that the upper thermal coloring layer does not develop color during thermal recording on the lower thermal coloring layer.
[0003]
Blue to ultraviolet light emitting diodes used in printers as described above have low luminous efficiency (light output / current) and energy conversion efficiency (light output / input power). As a result, there is a problem that the element temperature rises and the light emission efficiency further decreases. For this reason, how to output the emitted light in a desired direction, that is, whether to improve the utilization efficiency of the emitted light from the light emitting diode, is also a general purpose for display or This is also an important issue for light-emitting diodes for illumination.
[0004]
In order to solve such a problem, many light emitting diodes having a reflecting mirror around the chip or display devices using such light emitting diodes have been proposed. For example, a light emitting diode is bonded together on a substrate on which a large number of concave mirrors and electrical lead-out wirings are formed to complete the connection with the lower electrode, and then the electrical derivation to the upper electrode of the light emitting diode is performed. A light emitting diode type display device has been proposed in which wiring is completed in a lump and manufactured with high accuracy. (For example, see Patent Document 1)
In addition, a light emitting diode having a structure in which a light reflecting case having a chip hole and a wire hole is fixed to a substrate on which the light emitting diode chip is installed has been proposed, and the distance between the light emitting diode chip and the reflecting surface of the light reflecting case is proposed. It is described that the luminance can be reduced and the luminance density can be improved. (For example, see Patent Document 2)
In addition, through holes corresponding to the light-emitting diode chips are formed on the upper surface of the flexible substrate in which the light-emitting diode chips are arranged in a matrix, and a white pigment is included to improve light reflection. There has been proposed a light-emitting diode display device in which an insulating frame made of silicon rubber is joined and the through hole is filled with translucent silicon rubber. (For example, see Patent Document 3)
[0005]
[Patent Document 1]
JP-A-7-287535 [0006]
[Patent Document 2]
JP-A-8-32118
[Patent Document 3]
JP-A-6-301342
[Problems to be solved by the invention]
In the light-emitting device having the above-described reflecting mirror, the substrate and the reflecting mirror are different from each other because required characteristics are different between the substrate to be improved in heat dissipation and the reflecting mirror portion that is desired to be formed with a material that can be easily molded with higher accuracy. When the structure is separated, the light-emitting / reflecting pattern is deformed due to the deviation between the substrate and the reflecting mirror, resulting in luminance unevenness or illuminance unevenness. In addition, when mounted on a general printed circuit board at high density and emits light with high brightness, heat generated from the light emitting diode is large, and heat cannot be dissipated to the module substrate, leading to an increase in chip temperature and a decrease in heat generation efficiency. As a result, there arises a problem that luminance as a module is lowered.
[0009]
In view of the above circumstances, an object of the present invention is to provide a highly reliable light-emitting device with reduced luminance unevenness or illumination unevenness.
[0010]
[Means for Solving the Problems]
In the light emitting device of the present invention, a plurality of light emitting elements connected to the wiring are fixedly provided on a substrate on which an electrical lead-out wiring is formed,
A reflecting mirror that includes a plurality of first holes for extracting light from the light emitting element, and a side surface of the first hole reflects light emitted from the light emitting element to the periphery of the light emitting element in a light extraction direction of the light emitting element The light reflecting case is a light emitting device that is bonded on a substrate so that one of the light emitting elements faces one of the first holes,
The substrate and the light reflecting case are provided with alignment marks for aligning the substrate and the light reflecting case.
[0011]
The alignment mark provided on the substrate is desirably formed simultaneously with the same material as the wiring in the step of forming the electrical lead-out wiring.
[0012]
When the light reflecting case is made of an opaque material, the alignment mark formed on the light reflecting case can be viewed from above the alignment mark formed on the substrate when the light reflecting case is placed on the substrate. A rectangular second hole, and an alignment mark formed on the substrate is provided at a position facing the second hole at the time of alignment, and the four sides of the second hole are located inside the second hole. It is desirable to have a shape having four sides that are parallel to each other.
[0013]
It is desirable that a window for extracting light from the light emitting element is provided on the light reflecting case so as to close at least the first hole. As the window, glass, sapphire, or quartz having an anti-reflection coating on the upper and lower surfaces of the wavelength of emitted light is desirable.
[0014]
The light-emitting device described above may be used as a light source of a fixing unit that fixes recording data by irradiating fixing light onto a thermal recording paper on which thermal recording has been performed.
[0015]
【The invention's effect】
According to the light-emitting device of the present invention, a plurality of light-emitting elements connected to the wiring are fixed on a substrate on which an electrical lead-out wiring is formed, and a plurality of first holes for taking out light from the light-emitting elements are provided. A light reflecting case in which a side surface of the first hole is a reflecting mirror that reflects light emitted from the light emitting element to the periphery of the light emitting element in a light extraction direction of the light emitting element is formed on the substrate. A light-emitting device in which one of the light-emitting elements is bonded to one of the holes, and an alignment mark for aligning the substrate and the light reflecting case is provided on the substrate and the light reflecting case. As a result, the substrate on which the light emitting element is fixed and the light reflecting case are aligned with high accuracy, and the emitted light from the light emitting element can be efficiently reflected in the light extraction direction. To improve efficiency Kill. Thereby, luminance unevenness or illuminance unevenness can be eliminated in the light emitting device.
[0016]
Since the alignment mark provided on the substrate is formed simultaneously with the same material as the wiring in the step of forming the electrical lead-out wiring, there is no need to provide a separate step of forming the alignment mark. The positional deviation between the target lead-out wiring and the alignment mark can be prevented.
[0017]
When the light reflecting case is made of an opaque material, the alignment mark formed on the light reflecting case can be viewed from above the alignment mark formed on the substrate when the light reflecting case is placed on the substrate. A second hole having a rectangular shape, and an alignment mark formed on the substrate is provided at a position desired for the second hole at the time of alignment, and the four sides of the second hole are formed inside the second hole. Can be easily aligned by having a shape with four sides parallel to each other.
[0018]
By providing a window for extracting light from the light emitting element so as to close at least the first hole on the light reflecting case, it is possible to obtain good reliability over time. In particular, when the emitted light is in a short wavelength region, it is possible to prevent a deterioration in quality due to deterioration of the resin that occurs when a resin or the like is filled instead of the window.
[0019]
By using the above light emitting device as a light source of a fixing device for fixing recording data by irradiating fixing light to heat-sensitive recording paper on which thermal recording has been performed, a light source having good luminous efficiency and good luminance and illuminance It can be.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0021]
A light emitting device in which light emitting diodes are two-dimensionally arranged according to an embodiment of the present invention will be described. FIG. 1 shows a perspective view of the substrate and the light reflecting case on which the light emitting diode is fixed, of the light emitting device. A sectional view of one light emitting diode in a state where the substrate and the light reflection case are bonded is shown in FIG. 2A, and a partially enlarged view of FIG. 2B is shown in FIG.
[0022]
As shown in FIG. 1, the light emitting device according to the present embodiment has a 380 nm band on an aluminum substrate 11 provided with alternately formed p-side lead wires 15, n-side lead wires 16, and alignment marks 19. The surface of the light emitting diode 12 on which the p-side electrode 13 and the n-side electrode 14 are formed faces upward, the p-side electrode 13 is connected to the p-side lead-out wiring 15 by the wire 17, and the n-side electrode 14 Are connected to the n-side lead-out wiring 16 by a wire 18 and fixed in a matrix shape. On the aluminum substrate 11 provided with the light emitting diode 12, the first hole 22 facing the light emitting diode 12 and the substrate 11 are provided. A light reflecting case 25 comprising a glass plate 24 on a silicon substrate 21 provided with a second hole 23 facing the alignment mark 19 provided on the first is provided in the first reflection case 25. Emitting diode 12 to one of the holes 22 is made is bonded so as to face one. A non-reflective coating is applied to the upper and lower surfaces of the glass plate 24 with respect to the wavelength of light emitted from the light emitting diode. The side surface of the first hole 22 is provided with an aluminum film 20, and the side surface of the first hole 22 is a reflecting mirror that reflects light emitted from the periphery of the light emitting diode 12 in the light extraction direction. .
[0023]
The light-emitting diode 12 is a light-emitting diode that emits UV light of 380 nm, is formed by laminating a GaN-based semiconductor on a sapphire substrate, and has a p-side electrode and an n-side electrode formed on the upper surface in the stacking direction. The light emitting diodes 12 are arranged so that the positions of the electrodes are symmetrical with respect to the lead-out wiring, and adjacent light-emitting diodes across the lead-out wiring share one lead-out wiring on the n side and the p side. Yes. For this reason, the light emitting device according to the present embodiment is subjected to ON / EFF control for each vertical row.
[0024]
Next, details of one light emitting region will be described.
As shown in FIG. 2A, an insulating layer 26 is provided on the aluminum substrate 11, and a p-side lead-out wiring 15 and an n-side lead-out wiring 16 are formed thereon. The light emitting diode 12 is bonded to the aluminum substrate 11 by solder 27, and the light reflecting case 25 is bonded by solder 28.
[0025]
FIG. 2B shows an enlarged view of the region 30 in FIG. As shown in FIG. 2B, Ni30 is plated on the light emitting diode bonding surface of the aluminum substrate 11. The thickness of the plated Ni 30 is preferably as thin as possible because it has a lower thermal conductivity than aluminum. However, if it is too thin, a solder metal used for bonding, for example, tin lead, passes through Ni plated at the time of bonding and diffuses into the substrate 11, so about 1 to 2 μm, for example, is desirable. Even when cream solder is used, it is better to perform plating from the viewpoint of preventing defects such as chip peeling over time.
[0026]
Further, as shown in FIG. 2B, the p-side lead-out wiring 15 is a Ni film 34 (thickness of about 0.5 to 5 μm) for improving adhesion through an insulating layer 26 on the aluminum substrate 11. Copper 33 (thickness of about 0.05 to 2 μm), Ni film 32 (thickness of about 0.5 to 5 μm) for facilitating adhesion with a wire, and Au film 31 are laminated in this order. is there.
[0027]
Instead of the aluminum substrate 11, a ceramic substrate such as alumina or aluminum nitride, or a metal substrate such as an MC (metal core) substrate, a metal core substrate made of high heat-resistant copper, or an aluminum substrate can be used.
[0028]
Ni 35 and Au 36 are formed in this order on the bottom surface of the sapphire substrate 1 of the light emitting diode in order to reflect the emitted light upward. The high reflectivity film is not limited to the above metal film, and a high reflection layer made of a dielectric multilayer film may be formed. As the high reflection metal film, for example, chromium, nickel, titanium or tantalum is 0.005 to 1 μm. In addition, it is desirable to laminate about 0.05 to 3 μm of gold, silver or platinum in this order. The metal used for the uppermost layer is preferably selected in consideration of the wettability of the solder used for bonding the aluminum substrate 11 and the light emitting diode 12, the bonding strength, etc., but the heat generated from the element is made uniform over the entire bottom surface of the element. For this purpose, a metal having better thermal conductivity than the sapphire substrate, such as gold, is preferable.
[0029]
The alignment mark 19 formed on the aluminum substrate 11 is made of the same material as the p-side lead-out wiring 15 and the n-side lead-out wiring 16, and is a lithography in which the p-side lead-out wiring 15 and the n-side lead-out wiring 16 are formed. It is formed at the same time in the process. As a result, positional deviation between the lead-out wiring and the alignment mark can be prevented, and the alignment mark manufacturing process can be omitted.
[0030]
Next, a method for producing the light reflecting case 25 will be described.
[0031]
A first hole 22 serving as a reflecting mirror and a second hole 23 for alignment are formed on the surface of the silicon single crystal substrate 11 by a photolithography process. The resist alone reduces the adhesion between the silicon and the resist, and the etching solution that has entered the gaps unevenly forms a slope with vertical streaks, so a metal mask with a sufficient selectivity to the etching solution is required. It is better to use it. In this case, a metal mask such as tantalum or chromium is formed on the silicon substrate, and a window of a desired resist shape is opened by a photolithography process. Using this resist as a mask, the metal film is etched away by anisotropic dry etching such as chlorine-based or fluorine-based reactive ion etching. Next, an inclined reflecting mirror surface is formed by wet etching or dry etching with an aqueous solution of KOH having anisotropy in silicon. When (100) silicon is used, the angle of the reflecting surface with respect to the substrate is automatically 54.74. Thereafter, Si is thinned from the back by polishing or sandblasting to form the first hole 22 and the second hole 23.
[0032]
Next, a metal film having a high reflectivity with respect to light of 380 nm, for example, aluminum, gold, silver, or the like is formed from the reflecting mirror surface side by sputtering or the like. Further, a glass plate 24 on which an antireflective coating is applied so as to have a low reflectance in a range of at least ± 10 nm centered on 380 nm is bonded to the silicon substrate 21. Not only the glass plate but also sapphire or quartz can be used. In this embodiment, since silicon is used as the substrate of the light reflecting case, a certain surface appears automatically by anisotropic etching, and a reflecting surface can be easily produced.
[0033]
As a window material of a normal light emitting element, when the wavelength of light is 400 nm or more, an epoxy resin is potted in the first hole 22 and thermally cured is used. On the other hand, at a wavelength shorter than 400 nm, the epoxy resin is deteriorated by irradiation with UV light, and therefore a silicone resin is used. However, the silicone resin has a problem that it takes time to cure and productivity is lowered. In the present embodiment, light is efficiently extracted to the outside by the reflecting mirror made of the aluminum film 20 and the non-reflective coated glass plate 24, so that the light output due to the deterioration of the window material made of the resin as described above. It is possible to drastically suppress the decrease.
[0034]
Next, a method for mounting the light emitting device will be described with reference to FIGS.
FIG. 3 shows the alignment mark 19 formed on the aluminum substrate 11 when viewed from above the second hole 23 of the light reflecting case 25 when the light reflecting diode 25 is bonded to the aluminum substrate 11 on which the light emitting diode 12 is fixed. FIG.
[0035]
As shown in FIG. 1, the light emitting diode 12 is bonded to the substrate 11 on which the p-side lead-out wiring 15, the n-side lead-out wiring 16, and the alignment mark 19 are formed by solder. The light emitting diode 12 is fixed at a predetermined position on the aluminum substrate 11 by causing the alignment device to recognize the distance from the shape of the p-side electrode 13 and the n-side electrode 14 to the p-side lead-out wiring 15 and the n-side lead-out wiring 16. . Next, the p-side electrode 13 is connected to the p-side lead wire 15 by the wire 17, and the n-side electrode 14 is connected to the n-side lead wire 16 by the wire 18.
[0036]
Next, the light reflecting case 25 is placed on the aluminum substrate 11 on which the light emitting diodes 12 are fixed, and alignment is performed by looking through the alignment holes 19 formed on the substrate 11 from the second holes 23. At this time, as shown in FIG. 3, the alignment mark 19 formed on the aluminum substrate 11 is a cross, and the second hole 23 formed in the light reflecting case 25 is a regular square. These four sides and the four sides of the cross are parallel and the gaps a, b, c and d are equal to each other, and the substrate 11 and the light reflecting case 25 are aligned and bonded by solder. Thereby, deviations in the x, y direction and the rotation direction can be prevented, and alignment is performed with high accuracy. Therefore, a highly reliable light emitting device in which luminance unevenness and illuminance unevenness of emitted light is suppressed is obtained. Can do.
[0037]
Next, a light emitting device according to a second embodiment of the invention will be described. A cross-sectional view thereof is shown in FIG. In the figure, only a sectional view of one light emitting region is shown.
[0038]
In the light emitting device according to the present embodiment, the p-side electrode 43 and the n-side electrode 44 of the light-emitting diode 42 are bonded to the p-side lead-out wiring 15 and the n-side lead-out wiring 16 by solder 27, respectively. This aspect is the same as that of the first embodiment. The same elements as those in the above embodiment are denoted by the same reference numerals, and description thereof is omitted. The light emitting diode 42 has a p-side electrode 43 formed on the entire contact layer. Further, a gold plating 37 is applied between the n-side electrode 44 and the solder 27 in order to eliminate an electrode step.
[0039]
In the light emitting device according to the present embodiment, since the electrode side, that is, the side close to the light emitting layer is bonded to the aluminum substrate 11, heat can be efficiently radiated. Further, as shown in FIG. 5, by providing a heat sink 39 on the aluminum substrate 11 by using a heat conductive adhesive 38 such as silicon grease, it is possible to further improve heat dissipation, and to provide high reliability and electrical characteristics. Can be obtained.
[0040]
In the light reflecting case of the light emitting device according to the first and second embodiments, the substrate 21 is made of silicon, but it may be made of a transparent material such as plastic. In that case, the alignment mark provided on the light reflection case may be the second hole as in the above embodiment, or the surface of the light reflection case that is bonded to the substrate on which the light emitting diode is fixed is etched. May be provided. An example of the alignment mark provided by the etching or the like is shown in FIG. As shown in FIG. 6, a cross alignment mark 45 enlarged by a cross alignment mark 19 formed on the aluminum substrate 11 on which the light emitting diode 12 is fixed is provided on the substrate 21 of the light reflecting case 25 by etching. Then, alignment is performed so that the gaps a, b, c, and d between the alignment marks 19 and 45 are equal, and the two sides are parallel in the eight gaps e. It is possible to align.
[0041]
Moreover, about the shape of the reflecting mirror formed in the light reflecting case 25, since silicon was used for the substrate 21, a specific surface appeared by anisotropic etching to form a rectangular hole, but other materials were used. In this case, the hole is not limited to a rectangular shape but may be a circular or elliptical hole.
[0042]
In addition, for bonding the light emitting diode 12 to the aluminum substrate 11, it is desirable to seal with solder in consideration of deterioration due to light emitted from the light emitting diode 12, but the bonding position of the light emitted from the light emitting diode is preferable. Since it is not on the optical path, an organic adhesive may be used. Moreover, when bonding the silicon substrate 21 and the glass plate 24 in the light reflection case 25, an organic adhesive may be used for the same reason.
[0043]
Next, an embodiment in which the light emitting device of the present invention is used as a light source of a fixing device of a color thermal printer will be described. A schematic plan view of the light emitting device is shown in FIG.
[0044]
As shown in FIG. 7, the plurality of light emitting diodes 12 are connected in series in the main scanning direction X across the width of the paper, and the p-side electrode 13 and the n-side electrode 14 are connected in series to the electrical lead-out wiring 55 by a wire 56. This is a plurality of rows arranged to obtain a necessary light amount in the sub-scanning direction Y. On top of these light emitting diodes, a light reflecting case (not shown) having a hole serving as a reflecting mirror as described above is bonded.
[0045]
Using the fixing device having such a light source, the recording data is fixed by irradiating light onto the thermal recording paper 51 on which the thermal recording moving in the sub-scanning direction Y is performed. After irradiating light to the writing area once in three rows in the main scanning direction, light emission is stopped, the thermal paper is moved in the sub-scanning direction Y, and light is irradiated to the next writing area. In the past, when a fluorescent tube was used as the light source for the fixing device, a shutter or the like was installed so as not to irradiate light in conjunction with the thermal recording paper so as not to fix the next writing area. If a light emitting device using a light emitting diode having a small spot diameter is used as a fixing light source of a printer device as in the present invention, a clear image can be obtained, the device can be miniaturized, and mechanical It is possible to avoid a decrease in reliability due to a failure of the drive part.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a light emitting device according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view showing a light emitting region of the light emitting device. FIG. 4 is a cross-sectional view showing one light emitting region of the light emitting device according to the second embodiment of the present invention. FIG. 5 is a cross sectional view of the light emitting device according to the second embodiment provided with a heat sink. 6 is a plan view showing another form of alignment mark. FIG. 7 is a plan view showing an embodiment in which the light emitting device of the present invention is used as a light source of a fixing device.
11 Aluminum substrate 12 Light-emitting diode 13 p-side electrode 14 n-side electrode 15 p-side lead-out wiring 16 n-side lead-out wiring 17, 18 wire 19 alignment mark 20 aluminum film 21 silicon substrate 22 first hole 23 second hole 24 glass plate 25 Light reflection case

Claims (5)

A plurality of light-emitting elements connected to the wiring are fixed on the substrate on which the electrical lead-out wiring is formed,
A plurality of first holes for extracting light from the light emitting element are provided, and a side surface of the first hole reflects light emitted from the light emitting element to the periphery of the light emitting element in a light extraction direction of the light emitting element. A light reflecting case, which is a reflecting mirror, is a light emitting device in which one of the light emitting elements is adhered to one of the first holes on the substrate,
An alignment mark for aligning the substrate and the light reflecting case is provided on the substrate and the light reflecting case. 2. The light emitting device according to claim 1, wherein the alignment mark provided on the substrate is formed simultaneously with the same material as the wiring in the step of forming the electrical lead-out wiring. The light reflecting case is made of an opaque material, and the alignment mark formed on the light reflecting case is visible from above the alignment mark formed on the substrate when the light reflecting case is placed on the substrate. A rectangular second hole that enables
An alignment mark formed on the substrate is provided at a position facing the second hole during alignment, and has four sides parallel to the four sides of the second hole inside the second hole. The light-emitting device according to claim 1, wherein the light-emitting device has a different shape. 4. The light emitting device according to claim 1, wherein a window for extracting light from the light emitting element is provided on the light reflecting case so as to close at least the first hole. 5. The light emitting device according to claim 1, wherein the light emitting device is used as a light source of a fixing device for fixing recording data by irradiating fixing light onto heat-sensitive recording paper on which thermal recording has been performed.

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