JPH01225377A - Led array - Google Patents

Abstract

PURPOSE:To make an LED array have high density and brightness, by mounting a crystal layer including an active layer on a substrate and manufacturing an LED dot array after forming grooves which cut the active layer at least into a number of pieces in a crystal layer to manufacture an LED dot array and then, causing the width of each groove between LED dots to have a constant value or less, thereby mounting electrodes at the substrate and respective LED dots. CONSTITUTION:Each width of grooves which form LED dots where light emitting points are isolated one another is 20mum or less. This device is composed of a number of the LED dots P having a double hetero structure consisting of: a p-type GaAs substrate B; a p-type AlGaAS clad layer 1 where epitaxial growths are performed in order on the substrate B; a p-type AlGaAs active layer 2; and an n-type AlGaAs clad layer 3, n-side electrodes E1 which are mounted on the clad layer 3 as well as a p-side electrode E2 which is mounted at the substrate B. The grooves 5 cut the active layer 2 of the LED dots P into pieces. In this way, a number of independent light emitting points, that is, an LED dot array, is completed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an LED array that has high density and high brightness of LED dots per unit length, and particularly to an LED array that is optimal as a light source for an LED printer.

[Conventional technology]

A printer is a device that outputs computer processing results and text and graphic information on a display onto paper to create a hard copy.It can be roughly divided into line printers, which can print a line of paper at a time, and typewriters. There are serial printers that print one character at a time, and there are two types of printing methods: impact type, which prints by mechanically hitting a drum or belt, and non-impact type, which prints using static electricity, discharge phenomenon, ink, etc. There is.

Recently, non-impact printers with less noise are rapidly becoming popular in place of impact printers. Among non-impact type printers, laser beam printers, liquid crystal shutter printers, and LED printers are particularly in the spotlight, and their number of uses is increasing. Among these electrophotographic methods, LE
The D method was originally intended for use as a medium-speed aircraft, but
Compared to laser beam printers, there are no moving parts and fewer adjustment errors, creating the potential for ultra-high-speed printer capabilities. LED printers have a light source head that is completely solid-state and electronically scanned by using a focusing rod lens array and an LED array chip, and are known as small, highly portable electrophotographic printers.

An LED printer using an LED as a light source generally employs a method of discharging a desired portion of the charged surface of a photoreceptor using an LED, and developing and transferring the charged toner. For example, in an A4 size printer, this A4
It requires an array of LED dots corresponding to the length of the size, and the light from the LEDs is imaged onto the photosensitive surface by a focusing rod lens. This LED display element, as shown in Figure 6,
The light emitting parts 30, which are light emitting parts 30 each having one LED arranged at regular intervals, are electrically connected to the wiring part 31.

In this way, the LED head, which is a key device for LED printers that is especially suitable for high-speed printing, has become smaller, faster, and has higher printing quality.The first thing that has been able to achieve miniaturization is LED. This is because a technology for arranging array chips in a single row with high precision has been established.

At present, single-row arrays are in practical use for heads with resolutions of up to 400 dots/inch, and higher resolution is technically possible, but about 480 dots/inch is one line.
This is considered to be the limit of practical application of the column array method with the current technology. Furthermore, in order to increase speed, studies are also being conducted to obtain high output by increasing the efficiency of the LED itself. That is, an AlGaAs single heterojunction LED is used in place of the GaPAs homojunction LED which is the conventional LED material, and a high output of 0.6 W/d is obtained.

In order to achieve high printing quality, a high density of 400 dots/inch has been put into practice.

[Problem to be solved by the invention]

In this way, attempts are being made to develop non-impact type LED printers, which are expected to become the mainstream printers of the future, to further downsize, speed up, and improve print quality. Among these, achieving high density and high brightness of the LED array is an essential requirement for achieving high print quality.
Currently, the limit is 400 dots/inch at most.

In addition, as mentioned above, high brightness can be achieved by using Al instead of GaPAs.
It is desirable to solve this problem by using GaAs to create a single hetero structure or even a double hetero structure, but at this stage, double hetero structure LED arrays are not yet available. The highest value is about 2077 W/dot in combination with the terror structure.

Therefore, in view of the above-mentioned problems, it is an object of the present invention to provide an LED array with even higher density and higher brightness, particularly an LED array that can be used as a light source for an LED printer and achieve higher print quality. .

[Means to solve the problem]

The LED array that achieves the above purpose is manufactured by providing a crystal layer including an active layer on a substrate, forming grooves that cut the crystal layer into many pieces (at least up to the active layer), and fabricating an LED dot array.
It is characterized in that the width of the groove between the LED dots is 20.1 mm or less, and that an electrode is provided on the substrate and each LED dot.

In the LED array of the present invention, the width of the grooves forming the LED dots, which are the number of light emitting points separated from each other, is 20 or less, so that a precision of at least 400 dots/inch can be easily achieved. Minimum width (e.g. 2-
600 dots/inch can be achieved.

In addition, if ^lGa1la is selected as the semiconductor material for the active layer, higher output can be obtained compared to GaPAa, and if a single hetero or double hetero structure is adopted, higher brightness can be obtained.
For example, by using AlGaAs in combination with a double heterostructure, at least about 60 μW/dot can be expected.

Note that there is no particular restriction on the semiconductor material used for the LED array of the present invention, and examples include GaAs, GaPAs, and AlGa.
Materials such as As, GaP, and Ga1nP may be used by taking advantage of their characteristics.

〔Example〕

Hereinafter, the LED array 4 of the present invention will be explained in detail based on the drawings.

FIG. 1 shows an example of this. This LED array consists of a P-type GaAs substrate B and a p-type GaAs cladding layer 1. P-type^lGaA
s active layer 2 and n-type A] A large number of LED dots P (only some of which are shown in the drawing) of a double heterostructure consisting of a GaAs cladding layer 3 and an n-side electrode E1 provided on the cladding layer 3.
As is clear from FIG. 0, which has a p-side electrode E2 provided on the substrate B, each LED dot P is separated from each other by a groove 5, and the groove 5 cuts the active layer 2 of the LED dot P. This results in a large number of independent light emitting points, such as LEDs.
A dot array is formed. Note that if higher density is required, a structure may be adopted in which the p-type GaAs substrate B is removed.

The high-density light emitting pattern of the LED array with such a structure is
As shown in the figure, each LED dot P has a square prism shape, and the electrode E
Reference numerals 1 are elongated strips extending substantially vertically across the tops of the LED dots P, that is, the top of the cladding layer 3, and are arranged so as to reach each LED dot P alternately.

Here, for example, the radius W of the groove 5 is 5 ps, the size of the LED dot P is about a-4QPa, l) x5Q-, and in this case, it is possible to increase the density of the LED array to about 564 dots/inch. can. Furthermore, although it depends on the accuracy of the light emitting pattern, it is possible to make the width W up to about 2P, and 604 dots/inch can be achieved.

In the above embodiment, a considerably high output (at least 60 tIW/dot) can be easily obtained by combining AlGaAs and a double heterostructure, and since the printing speed of the printer is proportional to the optical output, high-speed printing can be achieved. .

Another example of the light emitting pattern of the LED array of the present invention is shown in FIG. 3, and a cross section of the LED array having the light emitting pattern is shown in FIG. is provided around the upper part of the LED dot P.

The semiconductor material constituting the substrate B and the LED dot P is the first
It is the same as shown in the figure. To give an example of the dimensions of this LED array, the size of the LED dot P is width x height -40
X 60P, width of groove 5 10 p-, width of electrode E1 on LED dot P 5 ps, α-90P1β-110-,
The definition is approximately 430 dots/inch.

Note that the LEDs of the present invention are not limited to those shown in the above embodiments.
There are no particular limitations on the method for manufacturing the array, and conventional methods may be used, but L is particularly important in the manufacturing process of LED arrays.
The etching method used to form grooves that separate crystal layers on a substrate into multiple independent layers during the production of an ED dot array is as follows:
In particular, it is preferable to use an etching method using a mixed gas of chlorine and hydrogen or chlorine and metal hydride gas (Japanese Patent Application No. 62-62216, Japanese Patent Application No. 74990-1982).
According to the etching methods disclosed in these documents, the anisotropic etching rate can be uniformly increased without being different depending on various compound semiconductor materials. Therefore, it is an etching technique that can easily and quickly form grooves with a uniform narrow width, and is useful for obtaining even higher density LED arrays. Incidentally, it is difficult to form such high-density grooves using normal wet etching.

〔Effect of the invention〕

Since the LED array of the present invention is configured as described above, it produces the effects described below.

Since the width of the groove for cutting the crystal layer including the active layer provided on the substrate into multiple pieces up to at least the active layer of the crystal layer is 20P or less, high-definition LED dots can be easily obtained and the light emitting pattern can be easily obtained. Depending on the accuracy, high density up to about 600 dots/inch can be achieved. Furthermore, if GaAs or the like is used as a semiconductor material and a single or even double hetero structure is adopted, a considerably high output (for example, about 100 μW/dot in a combination of AlGaAs and a double hetero structure) is possible.

Therefore, when the LED array of the present invention is used as a light source for a printer, particularly high quality printing can be obtained due to its high density and high brightness characteristics, and concomitantly, high speed printing can also be achieved.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of an embodiment of the LED array of the present invention;
2 is a schematic plan view showing the light emitting pattern of the array in FIG. 1, FIG. 3 is a schematic plan view showing another example of the light emitting pattern, and FIG. 4 is a schematic cross section of the LED array having the light emitting pattern shown in FIG. 3. FIG. 5 is a schematic diagram showing an example of a light emitting pattern of an LED array for a printer. B: p-type Ga^3 substrate 1: p-type AlGaAs cladding layer 2
:p type^lGaAs active layer 3
: N-type AlGa^3 cladding layer 5 : Groove p : LED dots El, E2 : Electrode Figure 2, Figure 3, Figure 5

Claims (2)

[Claims] (1) A crystal layer including an active layer is provided on a substrate, and grooves are formed to cut the crystal layer into many pieces up to at least the active layer.
A dot array was created, and the width of the groove between LED dots was 20
1. An LED array characterized in that the size is less than .mu.m, and an electrode is provided on a substrate and each LED dot. (2) The crystal layer has a double heterostructure, and the LE
The LED array according to claim 1, wherein the D array is a light source of an LED printer.