JP2002198559A - Semiconductor light emitting device and optical printer head using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high performance semiconductor light emitting device in which all light emitting elements can be driven uniformly at high speed so as to emit light without making its constitution complicated. SOLUTION: A plurality of light emitting elements 2 composed of a semiconductor thin film are arranged and installed on the surface of a substrate 1. Light intensity correction films 3 which are composed of a transparent resin, a glass or a ceramics are applied to surfaces of the elements 2. A roughening treatment according to the luminous luminance of the elements 2 is executed to the surfaces of the correction films 3 through which beams of light of the elements 2 are passed. As a result, the semiconductor light emitting device is constituted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an LED (Light Em
The present invention relates to a semiconductor light emitting device having a light emitting element such as an itting diode and an optical printer head using the same.

[0002]

2. Description of the Related Art Conventionally, optical printer heads such as LED printer heads have been used as exposure means for electrophotographic printers and digital copiers.

As a semiconductor light emitting device mounted on such an optical printer head, for example, as shown in FIG. 4, a single crystal thin film of a p-type compound semiconductor and a single crystal thin film of an n-type compound semiconductor are formed on the upper surface of a single crystal substrate 11. Light emitting element 1 formed by stacking
2 are arranged in a line, and a predetermined power is applied to the light emitting element 12 to convert electrons in the p-type compound semiconductor of the light emitting element 12 into an n-type compound semiconductor. Holes are injected into each of them, and they are recombined near a pn junction formed between the p-type compound semiconductor and the n-type compound semiconductor, and the energy generated at that time is converted into light. By emitting the light to the outside, it functions as a semiconductor light emitting device.

When the above-described semiconductor light emitting device is used for an optical printer head, light emitted from the light emitting element 12 is irradiated and imaged on an external photosensitive member via an optical system such as a rod lens array. A predetermined latent image is formed on the surface of the photoreceptor in accordance with the pattern of the irradiated light.

[0005]

When a semiconductor light emitting device is used in an optical printer head, in order to form a good latent image on the surface of a photoreceptor, the light emission luminance of all light emitting elements 12 is made as uniform as possible. It is important to keep them aligned.

However, in the above-described conventional semiconductor light-emitting device, the light-emitting element 12 is formed by a conventionally known semiconductor manufacturing technique, and the light-emitting element 12 manufactured by such a manufacturing method has a dislocation of a compound semiconductor forming the light-emitting element 12. It is practically impossible to control the density, the doping concentration, the film thickness, the composition, and the like all equally, and generally has a light emission variation of about ± 25%. Therefore, attempts have been made to adjust the power applied to the light-emitting element 12, the light-emission time, and the like in order to suppress the light-emission variation as small as possible. A correction circuit or the like is separately required, which complicates the configuration of an optical printer head or the like in which the semiconductor light emitting device is mounted, thereby increasing the manufacturing cost. There is a disadvantage that it is difficult to emit light and drive at high speed.

In the conventional semiconductor light emitting device described above, light generated inside the light emitting element 12 is emitted to the outside while spreading radially.
Most of the light emitted from 2 has escaped to the surroundings. For this reason, the light intensity of the light emitting element 12 is significantly reduced. For example, when the light of the light emitting element 12 is used for forming a latent image on the photoreceptor, the light intensity applied to the photoreceptor tends to be insufficient. This has the disadvantage that the image becomes unclear.

The present invention has been made in view of the above-mentioned drawbacks, and has as its object to provide a high-performance device capable of uniformly and rapidly emitting and driving all the light-emitting elements without complicating the configuration. An object of the present invention is to provide a semiconductor light emitting device and an optical printer head.

[0009]

According to a semiconductor light emitting device of the present invention, a plurality of light emitting elements made of a semiconductor thin film are provided on an upper surface of a substrate, and a transparent resin, glass or ceramic is provided on the upper surface of the light emitting elements. And a surface roughening process is performed on the surface of the light quantity correction film through which the light of the light emitting element passes, according to the light emission luminance of the light emitting element.

Further, in the semiconductor light emitting device of the present invention, the surface of the light quantity correction film is formed to be substantially spherical.
And a radius of curvature (R) of the surface of the light quantity correction film, a maximum thickness ( _Tmax ) of the light quantity correction film, and a width (W) of the upper surface of the light emitting element.
And the formula “0.5 ≦ R / W ≦ 1.0, 0.1 ≦ T _max / W
≦ 2.0 ”.

Further, the semiconductor light emitting device of the present invention is characterized in that the refractive index (n) of the light quantity correction film is set so as to satisfy the expression "1.5≤n≤1.7". It is.

An optical printer head according to the present invention is characterized in that a plurality of the above semiconductor light emitting devices are mounted on a circuit board.

According to the present invention, a light amount correction film made of a transparent resin or glass is deposited on the upper surface of the light emitting element, and the light emission luminance of the light emitting element is reduced on the surface of the light amount correction film through which the light of the light emitting element passes. The surface of the light-emitting element is irregularly reflected on the surface of the light quantity correction film to adjust the amount of light traveling upward from the light-emitting element. Is transmitted according to the surface state of the light amount correction film, and the amount of light traveling upward of the light emitting element is made uniform. As a result, the light intensity can be all equalized only by adjusting the surface roughness of the light amount correction film without using a special power supply circuit or a correction circuit, and the quality of the semiconductor light emitting device is improved. In addition to this, the configuration of the optical printer head on which the semiconductor light emitting device is mounted can be simplified, and the productivity can be improved.

In this case, since complicated data processing using correction data or the like is not required, the data processing speed can be maintained high, and the light-emitting element can emit and drive at high speed.

Further, according to the present invention, a table of the light amount correction film is provided.
The surface is formed to be substantially spherical, and the light amount compensation is performed.
The radius of curvature (R) of the surface of the positive film and the maximum thickness of the light amount correction film
(T _max) And the width (W) of the upper surface of the light emitting element are expressed by the formula “0.
5 ≦ R / W ≦ 1.0, 0.1 ≦ T_max/W≦2.0 ”
By setting it to satisfy, the light amount correction film
It functions as a chromatic lens to improve the light emitted from the light emitting element.
Can be focused on the
Is greatly improved.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a cross-sectional view of a semiconductor light emitting device according to one embodiment of the present invention, in which 1 is a single crystal substrate, 2 is a light emitting element, and 3 is a light amount correction film.

The single-crystal substrate 1 is made of single-crystal silicon or the like. A plurality of light-emitting elements 2 and a light-amount correction film 3 are disposed on the upper surface of the single-crystal substrate 1 and function as a supporting base material for supporting them.

When the single-crystal substrate 1 is made of single-crystal silicon, first, a conventionally known Czochralski method (pulling method) or the like is used to form an ingot of single-crystal silicon, and this is formed into a predetermined thickness. It is manufactured by slicing and polishing the surface.

The plurality of light emitting elements 2 provided on the upper surface of the single crystal substrate 1 are, for example, 600 dpi (dot)
(per inch), and a plurality of light emitting elements 2 constitute a light emitting element array.

The light-emitting element 2 is made of a compound semiconductor such as GaAs, AlGaAs, or AlGaInP, and a single-crystal thin film 2a of an n-type compound semiconductor and a single-crystal thin film 2b of a p-type compound semiconductor are sequentially laminated. The entire structure is formed so as to form a mesa shape (a hill shape).

Since these light emitting elements 2 have a pn junction inside, specifically, at the boundary between the n-type compound semiconductor 2a and the p-type compound semiconductor 2b, a predetermined light is applied through electrodes (not shown) or the like. Is applied, electrons are injected into the p-type compound semiconductor 2b, and holes are injected into the n-type compound semiconductor 2a. These are recombined near the pn junction, and the energy generated at that time is converted into light. , And emits light at a predetermined wavelength.

The light emitting element 2 is a conventional MOC.
An n-type compound semiconductor 2a made of AlGaAs or the like and a p-type compound semiconductor 2b made of AlGaAs or the like are sequentially stacked on the upper surface of the single crystal substrate 1 by employing a two-step growth method and a dislocation reduction method by a metal organic chemical vapor deposition (VD) method. Thereafter, the laminate is formed by mesa etching.

A light amount correction film 3 is individually applied to each upper surface of the light emitting element 2 described above. The light amount correction film 3 is made of a transparent material (light transmittance of 50% or more) made of an acrylic resin, a novolak resin, a phenol resin, a silicone resin, or the like.
A portion of the surface of the light quantity correction film 3 through which light emitted from the light emitting element 2 passes is subjected to a surface roughening process in accordance with the light emission luminance of the light emitting element 2.

That is, the surface of the light quantity correction film 3 is processed so as to be rougher as the light emission luminance of the light emitting element 2 is higher. Roughness is 0.003 μm in arithmetic average roughness Ra
In this case, the surface of the light amount correction film 3 is not subjected to a surface roughening treatment, and the surface of the light amount correction film 3 for which 5% of light is to be cut is roughened so that the surface roughness Ra becomes 0.05 μm. The surface of the light quantity correction film 3 for which 10% of light is to be cut is subjected to a surface roughening treatment so that the surface roughness Ra is 0.2 μm.

As described above, by roughening the surface of the light quantity correction film 3 in accordance with the light emission luminance of the light emitting element 2, a part of the light emitted from the light emitting element 2 can be partially roughened.
The amount of light going upward from the light emitting element 2 can be adjusted by irregular reflection on the surface of the light emitting element 2, and the amount of light going upward from the light emitting element 2 is made uniform by such adjustment.

Therefore, the light emission intensity of the light emitting elements 2 can be all equalized only by adjusting the surface roughness of the light amount correction film 3 without using a special power supply circuit or a correction circuit, and the quality of the semiconductor light emitting device is improved. In addition, the configuration of the optical printer head on which the semiconductor light emitting device is mounted can be simplified, and the productivity can be improved.

In this case, since complicated data processing using correction data or the like is not required, the data processing speed can be maintained high, and the light emitting element can emit and drive at high speed.

Further, the surface of the light quantity correction film 3 is formed in a substantially spherical shape, the radius of curvature (R) of the light quantity correction film surface, the maximum thickness (T _max ) of the light quantity correction film 3, and the width (W) of the upper surface of the light emitting element. ) And the formula “0.5 ≦ R / W ≦ 1.0, 0.1 ≦ T _max / W ≦
2.0 ", the light amount correction film 3 can function as a microlens with excellent light collection efficiency. Therefore, the light emitted from the light emitting element 2 can be favorably used by the light amount correction film. By condensing light, the intensity of light can be dramatically improved.

Here, when the ratio (R / W) of the radius of curvature (R) of the surface of the light quantity correction film 3 to the width (W) of the upper surface of the light emitting element is smaller than 0.5, the radius of curvature of the light quantity correction film 3 Becomes extremely small, so that the upper surface of the light emitting element 2 cannot be covered with the light quantity correction film 3 properly. If it is larger than 1.0, the radius of curvature of the light quantity correction film 3 becomes extremely large, so that the light collecting Light efficiency is greatly reduced. On the other hand, the ratio of the maximum thickness (T _MAX ) of the light quantity correction film 3 to the width (W) of the upper surface of the light emitting element (T _max /
If W) is smaller than 0.1, the maximum thickness of the light quantity correction film 3 becomes extremely thin, so that the upper surface of the light emitting element 2 cannot be satisfactorily covered with the light quantity correction film 3 and larger than 2.0. In this case, a large amount of liquid resin must be applied on the light emitting element 2 when the light amount correction film 3 is formed through a later-described liquid resin application and polymerization process. It flows out onto the crystal substrate 1 and a microlens having a desired thickness cannot be formed.

Accordingly, the surface of the light quantity correction film 3 is formed in a substantially spherical shape, and the radius of curvature (R) of the light quantity correction film surface, the maximum thickness (T _MAX ) of the light quantity correction film 3, and the width of the light emitting element upper surface ( W) is “0.5 ≦ R / W ≦ 1.0” and “0.1 ≦
It is preferable to set both so as to satisfy both of “T _max /W≦2.0”.

When the light quantity correction film 3 functions as a microlens as described above, the refractive index n is set to 1.
It is preferable to set within the range of 5 to 1.7, and materials satisfying such conditions include novolak resin and phenol resin.

The light amount correction film 3 is formed by selectively applying a liquid precursor such as a novolak resin to the upper surface of the light emitting element 2 by using a dispenser or the like, and applying the liquid resin to 150 ° C. Heating at high temperature of ~ 200 ℃
The surface of the light quantity correction film 3 is formed by polymerizing, and thereafter, the surface of the obtained light quantity correction film 3 is irradiated with a predetermined laser beam by a conventionally known laser ablation method, and the surface of the light quantity correction film 3 is roughened. To a predetermined surface roughness. At this time, the intensity, wavelength, irradiation time, and the like of the light applied to the light amount correction film 3 are adjusted to the emission luminance of the light emitting element 2 measured in advance so that the intensity of the light extracted to the outside becomes a target value. It is determined based on. For example, when the novolak resin light amount correction film 3 having a surface roughness of 0.003 μm in arithmetic average roughness Ra is roughened to 0.2 μm in arithmetic average roughness Ra by a laser ablation method, the irradiation light intensity is 0.5 J / Cm ² , an irradiation wavelength of 248 nm, and a pulse half width of 10 ns are used.

In the semiconductor light emitting device described above, predetermined power is applied to the light emitting element 2 to inject electrons into the p-type compound semiconductor 2b of the light emitting element 2 and inject holes into the n-type compound semiconductor 2a. These are p-type compound semiconductors 2b and n
The semiconductor light emitting device is recombined in the vicinity of a pn junction formed with the type compound semiconductor 2a, converts the energy generated at that time into light, and emits the light to the outside via the light amount correction film 3. Function as

When an optical printer head is manufactured using the above-described semiconductor light emitting device, as shown in FIG. 2, the above-described semiconductor cut into chips is formed on a circuit board 4 having a large number of circuit conductors 6. It is constituted by mounting a plurality of light emitting devices 5 and disposing a rod lens array 7 on these semiconductor light emitting devices 5 to selectively and individually emit light from the light emitting elements 2 of the semiconductor light emitting devices 5 based on image data. At the same time, the emitted light is transmitted to the rod lens array 7.
By irradiating and forming an image on an external photoreceptor via the optical disc, a predetermined latent image is formed on the surface of the photoreceptor, thereby functioning as an optical printer head.

It should be noted that the present invention is not limited to the above-described embodiment, and various changes and improvements can be made without departing from the gist of the present invention.

For example, in the above-described embodiment, the light amount correction film 3 is formed of a transparent resin, but instead, the light amount correction film 3 may be formed of silicon oxide, silicon nitride, titanium oxide, calcium fluoride, or the like. It may be formed using transparent ceramics or transparent glass.

In the above-described embodiment, the light emitting element 2 is made of GaAs, AlGaAs, AlGaInP, or the like.
It may be made of another LED such as GaAs or InGaAsP, an organic semiconductor of EL (electroluminescence) material, an inorganic EL material, or the like.

Further, in the above-described embodiment, the light amount correction film 3 is formed on the plurality of light emitting elements 2 formed in a mesa shape.
Are applied individually, but instead of this, FIG.
As shown in (2), the light emitting element 2 'may be of a planar type, or a single light amount correction film 3' may be commonly applied on a plurality of light emitting elements 2 '.

Further, in the above-described embodiment, when the light amount correction film 3 is formed on the light emitting element 2, the liquid resin is selectively applied to the upper surface of the light emitting element 2 using a dispenser or the like. If a photosensitive material is used as the liquid resin, even if the light amount correction film 3 is formed in a minute area having a width of about 10 μm to 40 μm, a small amount can be obtained by exposing and developing the photosensitive liquid resin. The light quantity correction film 3 can be easily formed. Therefore, when the light quantity correction film 3 is formed of a resin, it is preferable to use a photosensitive resin.

[0040]

According to the present invention, a light quantity correction film made of a transparent resin or glass is applied on the upper surface of the light emitting element, and the light emission of the light emitting element is formed on the surface of the light quantity correction film through which the light of the light emitting element passes. Each light emitting element is subjected to a surface roughening process in accordance with the luminance, and a part of the light emitted from the light emitting element is irregularly reflected on the surface of the light quantity correction film to adjust the amount of light going upward of the light emitting element. Is transmitted according to the surface state of the light amount correction film, and the amount of light traveling upward of the light emitting element is made uniform. As a result, without using a special power supply circuit or correction circuit, the light intensity can be all equalized only by adjusting the surface roughness of the light amount correction film,
The quality of the semiconductor light emitting device can be improved, and the configuration of the optical printer head on which the semiconductor light emitting device is mounted can be simplified to improve the productivity.

In this case, since complicated data processing using correction data or the like is not required, the data processing speed can be maintained high, and the light emitting element can emit and drive at high speed.

Further, according to the present invention, a table of the light quantity correction film is provided.
The surface is formed to be substantially spherical, and the light amount compensation is performed.
The radius of curvature (R) of the surface of the positive film and the maximum thickness of the light amount correction film
(T _max) And the width (W) of the upper surface of the light emitting element are expressed by the formula “0.
5 ≦ R / W ≦ 1.0, 0.1 ≦ T_max/W≦2.0 ”
By setting it to satisfy, the light amount correction film
It functions as a chromatic lens to improve the light emitted from the light emitting element.
Can be focused on the
Is greatly improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a semiconductor light emitting device according to one embodiment of the present invention.

FIG. 2 is a perspective view of an optical printer head configured using the semiconductor light emitting device of FIG.

FIG. 3 is a sectional view of a semiconductor light emitting device according to another embodiment of the present invention.

FIG. 4 is a sectional view of a conventional semiconductor light emitting device.

[Explanation of symbols]

1 ... single crystal substrate, 2,2 '... light emitting element, 3,
3 ': Light amount correction film, 4: Circuit board, 5: Semiconductor light emitting device

Claims (4)

[Claims] 1. A light-emitting device comprising a plurality of light-emitting elements comprising a semiconductor thin film disposed on an upper surface of a substrate, and a light-amount correcting film made of a transparent resin, glass or ceramics being deposited on the upper surfaces of these light-emitting elements. A semiconductor light emitting device in which a surface of a light quantity correction film through which light from an element passes is subjected to a surface roughening process in accordance with the emission luminance of the light emitting element. 2. The light amount correction film is formed so that the surface thereof has a substantially spherical shape, and the radius of curvature (R) of the light amount correction film surface, the maximum thickness (T _max ) of the light amount correction film, and 2. The semiconductor light emitting device according to claim 1, wherein the width (W) of the upper surface of the light emitting element is set so as to satisfy the following expression. 0.5 ≦ R / W ≦ 1.0 ··· 0.1 ≦ T max /W≦2.0 ··· 3. The semiconductor light emitting device according to claim 2, wherein the refractive index (n) of the light quantity correction film is set so as to satisfy the following expression. 1.5 ≦ n ≦ 1.7 ... 4. An optical printer head comprising a plurality of semiconductor light emitting devices according to claim 1 mounted on a circuit board.