JP3384479B2 - Integrated light emitting device for contact type optical printer - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applied to a light source of an optical printer, a copying machine, a writing light source of a projector using an optical writing type spatial light modulator, and a light source of a sensor. In particular, the present invention relates to a light-emitting element that can be miniaturized, has high external extraction efficiency, and has excellent directivity. 2. Description of the Related Art Today, with the progress of office automation, various information terminal devices have become widespread. Among them, information terminal devices using light emitting elements occupy an important position as optical printers and the like. Such a printer is
Since there is no noise and the printing speed is fast, It is attracting attention as such head for an optical printer to a tower Works in A equipment.
A device using an LED as a light emitting element is as follows. Since the response speed is nanoseconds and parallelization is possible, high-speed driving is possible. 2. Light emission can be controlled simply by inputting and outputting electric signals, so that driving can be performed at a wide range of speeds. 3. There is no start-up time for driving and no waiting time. 4. It has a compact and simple structure, and is excellent in miniaturization and adjustment and maintenance of the device. 5. Solid type, no moving parts, no noise and high reliability
It has excellent properties such as stiffness and has been developed in various ways. FIGS. 6 and 8 show an example of an image forming process of an electrophotographic printer and a schematic cross-sectional view of a light emitting element utilizing the characteristics of the light emitting element. The light emitting elements 803 are fixedly arranged in a line along the support substrate. The light-emitting element is provided with a pair of positive and negative electrodes for supplying power, and each electrode uses a pattern wiring or a driving IC and a conductive wire such as a metal wire 802 arranged on a supporting substrate for high resolution. The three-dimensional electrical connection is made. Further, 801 is provided as a light shielding member for narrowing down the light source via the transparent resin 804. When the LED array device using the light emitting element formed in this way is used in the electrophotographic printer shown in FIG. 6, the light emitting element of the LED array device 601 emits light by turning on and off the power from the drive circuit, A desired electrostatic latent image is formed on the photosensitive drum 603 previously charged in the charging chamber 604 via the lens 602. The formed image is printed out after development with toner from the toner supply chamber 605, transfer to the paper supplied from the paper supply chamber 606, and fixing. In order to realize a high-resolution image by using a printer head, it is necessary to reduce the size of the light emitting elements and to mount the light emitting elements in a small and high density. Therefore, the wiring of the light emitting element and the driving IC chip, etc.
An electrode, a conductive wire, and the like are intruded around the light emitting element. As a result, the light emitted from the light-emitting element is reflected by a reflective body such as the electrode or the conductive wire, and the reflected light becomes uneven in light emission. . Therefore, Japanese Patent Application Laid-Open No. 62-19 / 1987
In Japanese Patent Application Laid-Open No. 9073 and Japanese Patent Application Laid-Open No. Hei 7-22651, unevenness in density is eliminated by covering the reflective body with a black mask or forming a resin and a slit as a sealing member having high transmittance. . On the other hand, recently, as a semiconductor device capable of emitting short-wavelength light with high output, a nitride-based compound semiconductor (I
_{n X Al Y Ga 1-XY} N, 0 ≦ X ≦ 1,0 ≦ Y ≦ 1, 0 ≦
X + Y ≦ 1 ) has been developed. However, it is difficult for a light emitting device using a nitride-based compound semiconductor to grow a single crystal, and a semiconductor is formed on an insulating substrate such as a sapphire substrate in order to form a relatively good semiconductor film. It is. Such a nitride-based compound semiconductor needs to take out each of the positive and negative electrodes from the semiconductor surface side and has relatively high resistance, so that the mounting portion for taking out the electrodes becomes more complicated. Therefore, even if the above-described method is simply applied to a light-emitting device using a nitride-based compound semiconductor, it is not possible to sufficiently eliminate uneven light emission. In particular, as the density is increased for higher resolution and the size of the device itself is reduced, the influence of the mounting of the light emitting element is not only increased, but also the light emission unevenness is sufficiently eliminated unless the light spread of the light emitting element itself is narrowed. Can not. In the case of applying the above-mentioned LED array device, a wire for extracting an electrode is provided on the surface of the light-emitting element and is connected to a printed circuit board or the like. A mask must be formed on top of the wire. Therefore, the light is attenuated by the gap between the light emitting surface and the light shielding mask, and the light extraction efficiency as viewed from above the slit is deteriorated. Therefore, even if the density of the light emitting elements is simply increased in order to obtain a high resolution, there is a problem that the light intensity distribution is averaged and a sufficiently high resolution cannot be obtained due to uneven light emission and a decrease in light extraction efficiency. Further, when a mask as a light shielding member is formed on the upper portion of the wire, unnecessary light is suppressed to some extent, but a certain distance between the slit portion and the light emitting portion is required, which is not suitable for miniaturization. Therefore, a better light emitting element is required. The present invention solves the above-mentioned problems, and there is a need for a light-emitting element that has high directivity even when the density is increased and the size is reduced, and that has excellent light extraction efficiency without uneven light emission. [0008] The present invention provides a light-transmitting insulating material.
A first nitride-based compound half having a first conductivity type on a substrate
Conductor and first conductivity type on first nitride-based compound semiconductor
2nd conductivity type different from the above and separated into multiple for each light emitting part
Nitride semiconductor and first nitride-based compound
And a common electrode (403) formed on the semiconductor.
It is an integrated light emitting device. In addition, nitrogen is transmitted through a transparent insulating substrate.
Nitride-based compound semiconductor on the surface facing the nitride-based compound semiconductor
Part of the emitted light transmitted through the translucent insulating substrate from the conductor is shielded
It is also an integrated light emitting element having a light shielding member. Further
The light-shielding member is made of a conductive material and is connected to the ground.
It is an integrated light emitting device. [0009] Integration is possible by adopting the structure of the present invention.
The distance between the light emitting surface and the upper portion of the mask can be reduced to the thickness of the mask, and the size can be reduced. Also,
Since there is no unnecessary reflector or the like and the distance to the light emitting surface is short, light extraction efficiency is improved. Also, an arbitrary spot shape can be obtained by changing the mask shape. By adopting the structure of the present invention, a light emitting element free from destruction of a nitride compound semiconductor due to static electricity can be obtained. According to the structure of the present invention , the light reflected by the light-shielding member is reflected again by the electrode formed on the nitride semiconductor, so that a light-emitting element having a higher light emission rate can be obtained. . DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As a result of various experiments, the present invention has been developed to reduce unevenness in light emission and decrease in luminance caused when a nitride-based compound semiconductor light-emitting element is miniaturized. It is arranged via a light-transmitting insulating substrate, which is a support for a semiconductor light-emitting element, and is prevented by extracting light through the light-transmitting insulating substrate, thereby improving directional characteristics of light emission, increasing light extraction efficiency, and reducing size. The inventors have found that a light-emitting element can be used, and have accomplished the present invention. That is, the distance between the light emitting surface and the upper portion of the mask can be reduced to the thickness of the mask, and there is no need to arrange a mounting for electrical connection between the light shielding member and the nitride compound semiconductor. Accordingly, there is no uneven light emission due to the reflected light reflected by the mounting or light absorption by the mounting, so that light from the nitride-based compound semiconductor can be extracted as spot light and the light extraction efficiency can be improved. Further, a wire for electrical extraction to the semiconductor light emitting element can be blown from above the semiconductor light emitting surface, so that the light emitting portion can be downsized. Even if a wire is used for mounting, the emitted light emitted from the semiconductor light emitting device directly reaches the light shielding member through the transparent insulating substrate, so that the influence on the conductive wires arranged around the light emitting device is extremely small. Even if high-density mounting is performed, the influence of uneven light emission due to reflection from a conductive wire or the like is extremely small. When a nitride-based compound semiconductor is used as a light-emitting element, it is possible to use a short-wavelength semiconductor whose emission wavelength is close to ultraviolet light, which is suitable for high-density and high-brightness of the candela class. It is possible to emit light from ultraviolet light to red. Hereinafter, the configuration of the present invention will be specifically described in detail. [0015] (light blocking member 101) and the light blocking member 101 used in the present invention, intended for sealed anti scatter desired outside light caused to emit light emitted from the nitride-based compound semiconductor into a desired shape It is. Further, it is preferable that the light-shielding member does not have a risk of being deteriorated by ultraviolet light included from the emission wavelength of the nitride semiconductor and the spread of the wavelength. Therefore, as the light shielding member, a colored metal oxide film, various metals, and the like can be given. In particular, it is preferable to use a metal film from the viewpoint of ease of fine processing. When a metal film is used as the light-blocking member, heat released from the nitride-based compound semiconductor can be released to the outside via the translucent support. In addition, when the light-emitting element is driven at a high frequency, electromagnetic waves emitted from the nitride-based compound semiconductor can be absorbed, so that malfunction of the electronic device can be prevented. Furthermore, since the semiconductor has a light-transmitting property with respect to the emission wavelength of the light emitted by the semiconductor itself, a confinement effect by multiple reflection of light is generated by the electrode of the light-emitting element and the light shielding member, so that light extracted from the spot light can be improved. Specific examples of such a metal film include Ag, Au, Cu, Al, and alloys thereof. These metal films can be formed over a light-transmitting insulating substrate by a sputtering method, a vacuum evaporation method, or the like. The formed metal film has a desired shape, for example, a perfect circle,
After forming a resist film of a desired shape to form a hole such as an ellipse, square, rectangle, etc., it can be formed by etching, or a mask can be formed so that undesired portions are not deposited during sputtering or vacuum evaporation. good. After forming the metal film, a desired hole can be formed by etching. Further, it can be used for fixing a light emitting element in which a light shielding member is formed using a metal member having a hole to a substrate. Further, a contact type in which the light emitting element is printed in close contact with an optical recording medium 702 to which microcapsules containing a dye-based photopolymerization initiator, a monomer or a prepolymer and a dye precursor are added, or a photosensitive material such as a silver salt photograph. When used in an optical printer or the like, it is necessary to contact and move the light emitting element and / or the photosensitive material in order to expose the photosensitive material corresponding to the light emitting element or to discharge the photosensitive material. In this case, the semiconductor element may be destroyed by static electricity charged on the photosensitive material from the beginning or static electricity generated by friction caused by the movement. When a nitride-based compound semiconductor is used, unlike other semiconductors, it is easily damaged by static electricity. For this reason, the light-shielding member is made of a conductive material and is dropped to the ground such as an earth connection, so that the electric charge can be released and the electrostatic breakdown of the light emitting element using the nitride-based compound semiconductor can be prevented. Specifically, a method of releasing electric charges by electrically connecting the light-shielding member 101 and the metallized pattern 203 on the common support using the conductive paste 201, a method of fixing a light-emitting element metal plate on the light-shielding member, and the like. There are various methods such as a method for releasing electric charges by utilizing 301. When the electric charge is released by the conductive paste 201 or the like, the conductive paste 2 provided between the light shielding member 101 and the metallized pattern 203 of the common support as shown in FIG.
01 or the like so as not to short the p-type and n-type semiconductor side surfaces, at least a nitride-based compound semiconductor with insulators 202 and 302 such as SiO ₂ , Si ₃ N ₄ , Al ₂ O ₃ , TiN, silicon rubber or epoxy resin. Is preferably coated in advance. Further, the insulator 202 is preferably colored dark with a black pigment or the like to suppress light scattering. The case where the electric charge is released using the metal plate 301 as shown in FIG. 3 is the same as described above, but the light emitting element can be fixed by the metal plate. (Translucent Insulating Substrate 102) The translucent support 102 used in the present invention is a support substrate for a semiconductor light emitting device and a semiconductor light emitting device for transmitting light through the inside thereof to extract light. It is desirable that the transmittance of the emitted light be high. Further, the light-transmitting insulating substrate may be used as a support for forming a semiconductor light-emitting element, or after forming a semiconductor, a light-emitting surface may be attached to the light-transmitting support. Furthermore, the light emission of the nitride-based compound semiconductor is considered to include ultraviolet light due to the spread of an undesired emission wavelength region in the vicinity of ultraviolet light, and the light-transmitting insulating substrate formed of an organic material when used for a long time. It degraded such as by double bond parts material forming the or shielding member expires. Such deterioration not only causes coloring such as yellowing and reduces the light extraction efficiency, but also causes peeling of the organic material. Therefore, the light-transmitting insulating substrate is preferably made of an inorganic material. Specifically, sapphire, alumina, spinel, or the like is suitably used. The nitride used (nitride compound semiconductor 103, 104) the present invention based compound semiconductor, a liquid phase growth method or a MOCVD method or the like on a substrate In _X Al _Y Ga
_1-XY N (0 ≦ X ≦ 1, 0 ≦ Y ≦ 1 , 0 ≦ X + Y ≦ 1 )
A product obtained by forming the above semiconductor as a light emitting layer is used. Semiconductor structures include MIS junction, PI junction, and NI junction
Homo structure and having a pn junction, include the hetero structure to heterostructure or double. Further, the light emitting layer may have a single-well structure or a multi-well structure to have a quantum effect. A variety of emission wavelengths can be selected from ultraviolet light to red light depending on the degree of mixed crystal of the semiconductor. Various selections may be made according to the use of the light emitting element, such as the photosensitive characteristics of the photosensitive material. The shape of the electrode formed on the nitride-based compound semiconductor can be variously selected as shown in FIG . FIG. 4A shows a nitride-based compound semiconductor and a metal electrode 105 and a transparent electrode 401 on a light-transmitting insulating substrate for forming one light-emitting portion (corresponding to a hole of a light-blocking member) in one light-emitting element. This is a light emitting element formed with. FIG. 4 (B)
Is a light-emitting element in which a plurality of nitride-based compound semiconductors are separated for each light-emitting portion by etching on a long light-transmitting insulating substrate and a light-shielding member 402 is formed. Thereby, scattering of light between the light emitting elements can be suppressed. FIG.
(C) separates a plurality of conductive semiconductor layers of one of the nitride-based compound semiconductors for each light emitting portion on a long transparent insulating substrate by etching, and shares an electrode formed on the other conductive semiconductor. A light-emitting element formed as an electrode. Thus, a more integrated light-emitting element can be obtained. FIG. 4D shows that a nitride-based compound semiconductor is separated into a plurality of light-emitting portions on a long light-transmitting insulating substrate and 85% or more, more preferably 90% or more, of the surface of the nitride-based compound semiconductor is separated. It is composed of a reflective electrode. The light-emitting element of the present invention extracts light through a light-transmitting insulating substrate holding a nitride-based compound semiconductor. Further, since the semiconductor is substantially transparent to emitted light due to the band gap, it is preferable to provide a reflective electrode on the surface opposite to the light-transmitting insulating substrate. By using the reflective electrode, light can be effectively used as spot light while repeating reflection between the light shielding member and the electrode. When a plurality of light emitting portions, which are holes of the light shielding member, are arranged and formed in a line or a matrix, a light transmitting insulating substrate having a light emitting element for each light emitting portion is arranged and formed on a common substrate. Alternatively, a light-emitting element having a plurality of light-emitting portions over one light-transmitting insulating substrate may be used. (Drive IC 501) The drive IC 501 is provided to turn on and off the light emitting element, and can be formed integrally with the light emitting element to be downsized. Further, the driving IC can correct the light amount so that the light emitting element has a desired light output. In particular, when a plurality of light emitting elements are used, it is difficult to arrange the light emitting elements with the same light emission intensity, and the light quantity can be corrected by controlling the power supplied to the light emitting elements or controlling the light emission time. Further, the light output correction of the light emitting elements may be corrected in bit units of each light emitting element or may be corrected in chip units. In any case, individual characteristics can be corrected by the drive IC. (Common Support 505) As the common support 505, the light emitting elements 502, 503, 5
04, a drive IC 501 and the like are arranged and electrically connected and fixed by metallization patterns provided on a common support. When the common support is used for a full-color printer head or the like, R (red) G
(Green) B (blue) light emitting elements 502, 503, and 504 are stacked. Since the common support 503 also affects the direction of emitted light, it is preferable that the common support 503 has a small amount of warpage and undulation and has a smooth surface. Further, the heat radiation from the light emitting element not only shortens the life of the light emitting element itself, but also modulates the emission wavelength and drives the light emitting element.
This has a great effect on the element characteristics such as the output of C. Therefore, a common support having good thermal conductivity is preferable. Specific examples of such a common support include a ceramic substrate and a metal base substrate in which an insulating layer is formed on a metal base such as aluminum or stainless steel and a copper foil is adhered thereon. Hereinafter, reference examples of the present invention will be described in detail, but it goes without saying that the present invention is not limited thereto. REFERENCE EXAMPLE ( Reference Example 1 ) A sapphire substrate having a thickness of 400 μm was inserted into a vacuum chamber to form a nitride-based compound semiconductor on a light-transmitting insulating substrate, and TMG gas, NH 3 gas, and P-type were used. Or N
The buffer layer and the N-type and P-type gallium nitride semiconductors were respectively deposited at 5 μm and 1 μm by MOCVD growth method by flowing the type dopant-containing gas to form a semiconductor wafer having a PN junction. A part of the P-type semiconductor layer was removed by etching to form an N-type semiconductor electrode formation surface. Thereafter, W and Ti were stacked on the N-type semiconductor by sputtering to form an N-type electrode. Next, Al was deposited on the P-type semiconductor by sputtering to form a P-type electrode.
The N-type and P-type electrodes are formed so as to cover the P-type semiconductor surface and the N-type semiconductor surface, respectively, in order to improve light extraction efficiency by reflection between the light shielding members. The sapphire substrate surface of the semiconductor wafer thus obtained was mirror-polished by polishing. Ag was deposited to a thickness of 500 μm using a vacuum deposition method to form a metal film serving as a light-shielding member on a sapphire substrate subjected to mirror finishing. In order to form a hole as a slit of a desired shape in the metal film formed in this way, about 1 direct line is formed at the center of the light emitting element.
A desired resist film having a thickness of 00 μm was formed, and an unnecessary metal film was removed by etching. The resist film was removed to form a light shielding member having a hole having a diameter of about 100 μm at the center of the light emitting element on the sapphire substrate. Thereafter, a scribe line was drawn to obtain a light emitting device of 350 μm by an external force. 100 light emitting elements and 100 driving ICs were fixed on a metallized ceramic substrate, which is a common support, using an Ag paste to perform electrical connection. The output error of all the light emitting elements was adjusted to within 5% using the driving IC. Such a light emitting element was used for a printer head of an electrophotographic printer shown in FIG. A desired electrostatic latent image was formed on a photosensitive drum that had been charged in advance, and the image was printed out through development with toner, transfer to paper, and fixing. Comparative Example 1 A semiconductor wafer on which a PN junction was formed was cut into a 350 μm square in the same manner as in Reference Example 1 instead of the light shielding member formed on the sapphire substrate. The sapphire substrate of this light emitting element is fixed to a common support, and
0 were fixed on a common support. After each electrode of the light emitting element was electrically connected to the drive IC by wire bonding, an epoxy resin as a light-transmitting resin was applied on the common support and cured. Thereafter, in the same manner as in Reference Example 1, an Ag film having a hole having a diameter of 40 μm was formed on the resin. For comparison, the same electrophotographic printer as in Reference Example 1 was incorporated and printed. As a result of confirming the printed out with a microscope, the printed out of Comparative Example 1 was lighter in printing and had uneven density compared to the printed out of Reference Example 1. In the relative comparison of the output image with respect to the input image, Comparative Example 1 showed about 15% more bleeding than Reference Example 1. Reference Example 2 R (red) G (green) B as a contact type optical printer head
Light emitting elements capable of emitting each wavelength of (blue) are formed in a line for each wavelength. As a red (660 nm) light emitting element, P-type GaAlAs and N-type GaAlAs were continuously formed on a P-type gallium arsenide substrate by a temperature difference liquid crystal growth method, and a semiconductor wafer having a PN junction was formed on a conductive substrate. . The semiconductor wafer for red has a metal film to be an electrode formed on both sides and a light extraction hole on one side with a diameter of 100 μm.
Provided. After the scribe line was drawn, the light was separated to 300 μm using external force to form a light emitting device. On the other hand, blue (470 nm) and green (52 nm)
For the light emitting element 5 nm), to form a semiconductor wafer having a pn junction to the n-type及beauty p-type gallium nitride compound to form a semiconductor light-transmissive insulating substrate on a sapphire substrate by MOCVD. The formed semiconductor wafer was electrically separated into 280 μm square by etching on a sapphire substrate . Partially etched p-type semiconductor and n
After exposing the mold electrode formation surface, a metal film to be a positive electrode and a negative electrode was formed on the entire surface of each separated semiconductor.
Next, a mask was formed on the sapphire substrate, and an Ag film was deposited as a light shielding member to a thickness of 20 μm by a sputtering method using Ag as a target. 100μm diameter after removing the mask
The light shielding member having the holes was formed. 300 each
After a scribe line was drawn to μm × 1500 μm, separation was performed by an external force to form a line-shaped light emitting element. The thus formed RGB light emitting elements were formed in a line on a ceramic substrate on which a metallized pattern was formed by soldering, thereby forming an optical printer head. This was used as a contact-type optical printer head as shown in FIG. 7, and a silver halide photograph was carried in and out, the optical printer head 701 was moved and exposed to light, and then developed. Further, the nitride-based compound semiconductor was not destroyed even when used repeatedly. As described above, the light emitting device of the present invention can be miniaturized, has high external extraction efficiency and excellent directivity, and a light emitting device using the same. Can be.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic sectional view of a light emitting device of the present invention. FIG. 2 is a schematic sectional view of another light emitting device of the present invention. FIG. 3 is a schematic sectional view of another light emitting device of the present invention. FIG. 4 is a schematic plan view showing an example of an electrode configuration of the light emitting device of the present invention. FIG. 5 is a schematic plan view of an optical printer head using the light emitting device of the present invention. FIG. 6 is a schematic cross-sectional view showing the operation of an electrophotographic printer using the light emitting device of the present invention. FIG. 7 is a schematic cross-sectional view showing the operation of a contact printer using the light emitting device of the present invention. FIG. 8 is a schematic sectional view of a light emitting device for comparison with the present invention. [EXPLANATION OF SYMBOLS] 101 ..... light shielding member 102 ----- translucent insulating substrate 103 · · · · · n-type nitride semiconductor 104 · · · · · p-type nitride semiconductor 105 ... ··· Electrode 106 ···· Solder 107 ···· Ceramic substrate 201 on which metallized pattern is formed ···· Conductive paste 202 ···· Epoxy resin 203 ····· Connected to ground Metallized pattern 301 ... Metal plate 302 ... Silicon oxide 303 as an insulating member ... Metallized pattern 401 connected to ground ... Transparent electrode 402 ... ... Light-shielding member 403... Common electrode 404... Aluminum electrode 501 with high reflectivity... Driving IC chips 502, 503, 504.・ ・Common support 601 LED array 602 Lens 603 Photosensitive drum 604 Charging chamber 605 Toner supply chamber 606 Paper Supply chamber 701 Optical printer head 702 Photoconductor 703 Photoconductor supply drum 704 Photoconductor supply chamber 705 Support 801 ... Shielding member 802... Conducting wire 803... Light emitting element 804.

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Claims (1)

(57) [Claim 1] A first nitride-based compound semiconductor having a first conductivity type on a light-transmitting insulating substrate, and a first nitride-based compound semiconductor on the first nitride-based compound semiconductor. A second nitride semiconductor having a second conductivity type different from the first conductivity type and separated by a plurality of light emitting portions, and a common electrode formed on the first nitride compound semiconductor ( 403) The integrated light-emitting device for a contact type optical printer having the above-mentioned, wherein the nitride-based compound semiconductor is interposed via the light- transmitting insulating substrate.
Light from the nitride-based compound semiconductor
Shielding member that blocks part of the emitted light transmitted through the conductive insulating substrate
And the blocking member has a conductive portion connected to ground.
Integrated light emitting device for contact type optical printers. "