JP3306130B2 - Light emitting diode array device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting diode array device in which a plurality of light emitting areas used as a light source of an electrophotographic printer are arranged in a straight line.

[0002]

2. Description of the Related Art In recent years, as the amount of information processing has increased, there has been a great demand for high-speed, high-resolution, low-noise electrophotographic printers, and their development has been promoted. As this light source, a light emitting diode array device having a plurality of light emitting regions arranged in a straight line is used. The one with a resolution of 400 dpi has been put to practical use.

FIG. 6 is a schematic view showing a conventional light emitting diode array device, FIG. 6 (a) is a plan view, and FIG.
Shows a cross-sectional view taken along the line II. This conventional device is disclosed in "Hitachi Cable, No. 5, pp. 29-32, 1985.12". In the figure, reference numeral 1 denotes a rectangular p-type GaAs substrate.
On a substrate 1, a p-type GaAlAs layer 2 is formed. A plurality of n-type GaAlAs layers 3 are provided at a central portion on the p-type GaAlAs layer 2 in the longitudinal direction.
The light emitting region 8 is formed by a pn junction between the As layer 2 and the n-type GaAlAs layer 3.
Is formed. An n-type GaAs layer 4 is formed on the n-type GaAlAs layer 3, and an insulating layer 5 is formed on the surface except on the n-type GaAs layer 4. An individual electrode 6 is provided on each n-type GaAs layer 4.
The individual electrodes 6 are alternately drawn to opposite ends of the p-type GaAlAs layer 2 in the width direction. On the lower surface of the p-type GaAs substrate 1, a common electrode 7 is provided.

In the conventional device having the above-described structure, light is emitted from the light-emitting region 8 (pn junction surface) by energizing the individual electrode 6 and the common electrode 7, and this light passes through each n-type GaAlAs layer 3. It is taken out. N-type GaAlAs at this time
In order to suppress the light absorption in the layer 3, the n-type GaAlAs
The composition ratio is set larger than the Al composition ratio of the p-type GaAlAs layer 2.

[0005]

The light emitting diode array device needs to be connected to a driving IC for driving the device.
The bonding between the pattern electrode formed on the metal wire or the film and the individual electrode 6 drawn from the light emitting region 8 is performed. In order to perform this bonding, an electrode pad having a size of about 100 μm square or more is required in the individual electrode 6. In the light emitting diode array device having a resolution of 400 dpi, the pitch at which the light emitting regions 8 are provided is about 60 μm.
Therefore, even if the individual electrodes 6 are alternately pulled out as described above, the space that can be used as an electrode pad is 120 μm. Therefore, with the configuration of the conventional apparatus, it is difficult to obtain a resolution of 400 dpi or more, which is increasing in demand in recent years. Therefore, a configuration in which the electrode pads are arranged in two rows on one end side to increase the resolution is conceivable. However, in this case, the element area becomes large, which is not appropriate. In recent years, there has been an increasing demand for devices capable of shading gradations.
Are arranged in a single row, so it can be considered that the only way to realize this is to control the current. In this case, a new problem arises such as the necessity of introducing a control circuit.

The present invention has been made in view of such circumstances, and has a configuration in which a plurality of light emitting regions are provided so that light emission can be performed independently for each column. It is an object of the present invention to provide a light emitting diode array device capable of achieving a higher resolution or a gray scale.

[0007]

According to a first aspect of the present invention, there is provided a light emitting diode array device, comprising: a light emitting region row in which a plurality of light emitting regions each formed of a pn junction layer laminated on a substrate are arranged in one direction; And a common electrode common to a plurality of light emitting regions, the light emitting region array having a plurality of light emitting region columns on the same substrate. A plurality of contact layers provided for each light emitting region column and in contact with a lower layer of the pn junction layer; and a plurality of contact layers provided in contact with the plurality of contact layers and configured to independently supply current to each light emitting region column. A common electrode, and before the individual electrodes conduct.
Insulating ridges between adjacent light emitting region rows on the substrate
And the light emitting area between the adjacent light emitting area rows is
The substrate is electrically separated by the edge. A light-emitting diode array device according to a second invention is characterized in that, in the first invention, the light-emitting regions in the drawing direction of the individual electrodes are arranged in a staggered manner.

[0008]

According to the first aspect of the present invention, when the light emitting regions are arranged side by side on the same line in the drawing direction of the individual electrodes, the light is irradiated to the same point on the photosensitive drum by independently supplying current to the light emitting regions. Since the number of times can be changed, it is possible to provide a gray scale.

Further, according to the second aspect of the present invention, it is possible to increase the resolution by arranging the light emitting regions in a staggered manner in the direction in which the individual electrodes are led out.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings showing the embodiments. FIG. 1 is a schematic view showing a first embodiment of the light emitting diode array device according to the first invention.
1A shows a plan view, and FIG. 1B shows a cross-sectional view taken along the line II-II. 9 in the figure is about 8000 μm in total length and about 1100 μ in width
The insulating GaAs substrate 9 has a linear ridge 9a formed in the longitudinal direction at the center of the insulating GaAs substrate 9 by etching of the insulating GaAs substrate 9. On both sides of the ridge 9a, the p-type GaAlAs layer 2 is formed in two rows separated by the ridge 9a. On both sides of the p-type GaAlAs layer 2, a p-type GaAs layer 10 as a lower contact layer is formed.

A plurality of n-type GaAlAs layers 3 are provided on the p-type GaAlAs layer 2 in the longitudinal direction, and an n-type GaAs layer 4 as an upper contact layer is formed on the n-type GaAlAs layer 3. . The pn of the p-type GaAlAs layer 2 and the n-type GaAlAs layer 3
The light emitting region 8 is formed by bonding. And the common electrode
An insulating layer 5 is formed on the surface excluding the formation region 11 and the n-type GaAs layer 4, and the insulating layers 5 are arranged in the width direction of the p-type GaAlAs layer 2.
One individual electrode 16 is provided over each of the light emitting regions 8, and the individual electrodes 16 are alternately drawn to one end in the width direction. On the p-type GaAlAs layer 2 outside the individual electrodes 16, common electrodes 11, 11 having a width of about 10 μm are provided in the longitudinal direction.

In the apparatus of the present invention having the above configuration,
When an electric current is applied to the individual electrode 16 and an electric current is applied to one or both of the common electrodes 11, 11, the electric current flows through the individual electrode 16, the n-type GaAs layer 4, the n-type GaAlAs layer 3, the p-type GaAlAs layer 2, and the p-type The light flows through the GaAs layer 10 and the common electrode 11 and emits light in the light emitting region 8 (pn junction surface). This light is extracted outside through each n-type GaAlAs layer 3. In order to suppress light absorption in the n-type GaAlAs layer 3 at this time, the Al composition ratio of the n-type GaAlAs layer 3 is changed to p-type GaAlAs.
It is larger than the Al composition ratio of the layer 2.

FIGS. 2 and 3 are explanatory views showing a method of manufacturing the light emitting diode array device shown in FIG. First, Fig. 2 (a)
As shown in FIG. 7, a ridge 9a (width 10 to 20 .mu.m, height 3 .mu.m) is formed in the longitudinal direction at the center of the insulating GaAs substrate 9 by photolithography. The thickness of the insulating GaAs substrate 9 where the ridge 9a is not formed is about 350 μm. Next, at the position where the light emitting region row (each width 50 μm) is formed and on the ridge 9a
An oxide film 13 (4000 mm thick) of SiO ₂ or the like is formed (FIG. 2).
(b)), a p-type GaAs layer 10 (thickness 3 μm) is
A crystal is grown by a (liquid phase epitaxy) method (FIG. 2C). After removing the oxide film 13, the p-type GaAlAs layer 2 (thickness 4 μm at the light emitting region forming position), the n-type GaAlAs layer 3
(Thickness 3 μm) and n-type GaAs layer 4 (thickness 0.5 μm)
Lamination is performed by the PE method (FIG. 2D).

Then, the p-type GaAl other than the light-emitting region column forming position
The As layer 2, the n-type GaAlAs layer 3 and the n-type GaAs layer 4 are removed and n
The light emitting region 8 is separated so that the GaAlAs layer 3 has a width of 40 μm and a length of 50 μm square, and the n-type GaAs layer 4 has a width of 10 μm and a length of 30 μm square (FIG. 3E). Further, on the n-type GaAs layer 4 and on the common electrode 11
Insulation film 5 such as SiO ₂ (thickness 4000)
Å) is formed (FIG. 3 (f)), and the individual electrodes 16 (thickness 4000 Å) made of Sn-Au are alternately drawn out to different end sides over the two light emitting regions 8 arranged in the width direction. And finally p-type Ga
Common electrodes 11 and 11 made of Zn-Au are formed on both ends of the As layer 10 (FIG. 3 (g)).

FIG. 4 is a schematic view showing a second embodiment of the first invention. FIG. 4 (a) is a plan view, and FIG.
6 shows a cross-sectional view taken along line VI. In this embodiment, three light emitting area rows are provided. The light emitting areas 8a ..., 8c ... in the outer two rows are p
P-type Ga on the insulating GaAs layer 12 formed on the
The AlAs layer 2 is formed, and the light emitting regions 8b in the middle row are formed.
In FIG. 1, a p-type GaAlAs layer 2 is formed on a p-type GaAs substrate 1. These light emitting regions 8a, 8b, 8c are electrically separated by ridges 12a, 12a formed by etching the insulating GaAs layer 12. On the other hand, a common electrode 7 is formed on the lower surface of the p-type GaAs substrate 1. One individual electrode 26 is provided over three light-emitting regions 8a, 8b, 8c arranged in the width direction, and is alternately drawn to different end portions. Other configurations are shown in FIG.
This is the same as the configuration shown in FIG. In such a light emitting diode array device, it is possible to select which column of the light emitting regions 8a, 8b, 8c emits light depending on which of the common electrodes 7, 11, 11 is energized. That is, when the common electrode 11 is selected, the current flows through the individual electrode 26, the n-type GaAs layer 4, and the n-type GaAl
The current flows through the As layer 3, the p-type GaAlAs layer 2, the p-type GaAs layer 10, and the selected common electrode 11, and when the common electrode 7 is selected, the current flows to the individual electrode 26, the n-type GaAs layer 4, the n-type GaAlAs layer 3, p-type GaAl
Light flows through the As layer 2, the p-type GaAs substrate 1, and the selected common electrode 7, and emits light.

In the apparatus of the present invention shown in FIGS. 1 and 4, a plurality of light emitting areas are arranged on the same line in the width direction of the substrate. Can be changed, and gradation of light and shade can be given.

FIG. 5 is a plan view showing an embodiment according to the second invention. The configuration is the same as that shown in FIG. 1, but the arrangement positions of the light emitting regions 8 are staggered (alternate) in the width direction of the element. In this case, as in the case of FIG.
Individual electrodes 16 are formed for each of the two light emitting regions 8 and are alternately drawn to different end portions. In the device of the present invention shown in FIG. 5, since the light emitting regions are arranged in a staggered manner in the width direction of the substrate, the resolution can be increased by controlling the light emission for each column. Note that the same effect can be obtained even if the p-type and the n-type are interchanged in all the embodiments described above.

[0018]

As described above, the light-emitting diode array device according to the present invention has a structure in which a plurality of light-emitting regions are provided and individual electrodes are provided for each of the plurality of rows.
The number of electrode pads can be smaller than the number of light emitting regions. Moreover, a plurality of light emitting region rows are provided on the same substrate,
The adjacent emitters on the substrate which are conducted by the individual electrodes
An insulating ridge is provided between the optical region rows, and the adjacent light emitting
Since the light emitting regions between the region rows are electrically separated on the substrate side by the ridges, the light emitting regions between the light emitting regions of each light emitting region column are separated.
A light-emitting diode array in which electrical separation on the substrate side is reliably performed can be easily manufactured on the same substrate. If the light emitting regions of the plurality of columns are arranged on the same line in the drawing direction of the individual electrodes, light emission of each column is controlled to make the number of emitted light different, so that gradation of light and shade can be achieved. In addition, if the plurality of rows of light emitting regions are arranged in a staggered manner in the drawing direction of the individual electrodes, the present invention is excellent in that high resolution can be realized by controlling the light emission of each column to vary the number of emitted light. It has the effect.

[Brief description of the drawings]

FIG. 1 shows a first embodiment of a light emitting diode array device according to the present invention.
It is a schematic diagram which shows an Example.

FIG. 2 is an explanatory view showing a method of manufacturing the light emitting diode array device shown in FIG.

FIG. 3 is an explanatory view showing a method of manufacturing the light emitting diode array device shown in FIG.

FIG. 4 shows a second embodiment of the light-emitting diode array device according to the present invention.
It is a schematic diagram which shows an Example.

FIG. 5 shows a third embodiment of the light-emitting diode array device according to the present invention.
It is a schematic diagram which shows an Example.

FIG. 6 is a schematic view showing a conventional light emitting diode array device.

[Explanation of symbols]

 2 p-type GaAlAs layer 3 n-type GaAlAs layer 4 n-type GaAs layer 5 insulating layer 8 light-emitting area 9 insulating GaAs substrate 9a ridge 10 p-type GaAs layer 11 common electrode 16 individual electrode

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H01L 33/00 JICST file (JOIS)

Claims (2)

(57) [Claims] 1. A light-emitting region row in which a plurality of light-emitting regions each formed of a pn junction layer laminated on a substrate are arranged in one direction, and a plurality of light-emitting regions are drawn out from the light-emitting regions in a direction intersecting with the juxtaposition direction. In a light emitting diode array device including a plurality of individual electrodes and a common electrode common to a plurality of light emitting regions, the light emitting diode array device has a plurality of the light emitting region columns on the same substrate, and is provided for each of the light emitting region columns. A substrate provided with a plurality of contact layers in contact with the lower layer and a plurality of common electrodes provided in contact with the plurality of contact layers and for independently supplying current to each light emitting region row, and electrically connected to the individual electrodes;
An insulating ridge is provided between the adjacent light emitting region rows above.
The light emitting region between the adjacent light emitting region columns is
A light-emitting diode array device electrically separated on the substrate side by the above method . 2. The light-emitting diode array device according to claim 1, wherein the light-emitting regions in the drawing direction of the individual electrodes are arranged in a staggered manner.