JPH0255157A - Led array and driving method - Google Patents

Abstract

PURPOSE:To obtain a high density LED array without limit in size of an electrode plate by alternately aligning n-type and p-type LEDs connected at electrodes of base side all to one common electrode, providing one driving electrode for a pair of adjacent n-type and p-type LEDs, and separating the applications of driving voltage to the n-type and p-type LEDs in a timing manner. CONSTITUTION:n-type and p-type arrays 101 and 102 are formed adjacently, and the central interval 103 becomes 12 of the write pitch (p) of a LED printer. Driving electrodes 104 disposed at both sides of the array are respectively connected to the electrodes of n-type and p-type LEDs 105 and 106 disposed in a zigzag manner. On the other hand, a signal S2 is of the driving signal of a p-type LED 304, and both the signals are applied as those which do not simultaneously become ON. The signals S1, S2 are respectively input to terminals 301 and 302 to turn OFF transistors 305, 306.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to the configuration of an LED array and its driving method, and particularly to an LED array and its driving method suitable for realizing an extremely high-density LED array.

[Conventional technology]

L E D (Light Emission Dio
abbreviation for de: LED (light emitting diode) arranged in an array
The array has the following advantages when used as an optical recording head of an optical printer. (1) The optical path length is short and the number of parts is small, making it compact and simple. (2) Since there are no moving parts in the head, recording performance is high and adjustment of the optical system is easy. (
3) Individual scanning is possible with a driving voltage of 5V or less, which is advantageous for combination with other devices and systemization.

An example of this LED array is shown in ``High-speed, high-definition LED printer using rGaAQAs'' by Kiyohiko Tanno, Proceedings of the 3rd Non-impact Printing Technology Symposium of the Electrophotographic Society, PP113-116 (1986). There is. The structure of the array viewed from above is shown in FIG. 5. Driving electrodes 502 are attached alternately on both sides of the upper surface of dots 501 composed of LEDs, and current flows through the driving electrodes. Luminous dot 501 (LE
D) emits light. “The structure of each LED is mainly made of GaAs, as will be shown in the embodiments of the present invention later.

[Problem to be solved by the invention]

Increasing the definition of LED arrays is essential for realizing high-quality LED printers, and in recent years, as mentioned in the above literature, 400 dot/1 nch arrays have been announced, and even higher density arrays are under development. be. The problem here is the size of the electrode plate drawn out from each LED. For example, in the LED array of the above-mentioned document, the width is 100 μm.
It's like a meeting.

If the electrode plate becomes smaller due to refinement, wire bonding will no longer be possible.

An object of the present invention is to provide a high-density LED display without being limited by the size of the electrode plate, and also to provide a method for driving the high-density LED array.

[Means to solve the problem]

The purpose of the above is to
There are two types, type and n type, and we focused on the fact that their reverse breakdown voltage is higher than the normal drive voltage.
EDs are arranged alternately, and one of adjacent n-type and p-type LEDs
This is achieved by providing one drive electrode for each pair, and by temporally separating the application of drive voltages to the n-type and p-type LEDs connected to one drive electrode.

[For production]

If two LEDs are connected to one drive electrode.

When the dimensions of the drive electrodes are constant, twice as many dots can be arranged compared to the conventional configuration of one drive electrode for each LED, and the LED array can be made more dense. moreover,
Since the drive times of the n-type and p-type LEDs connected to the same drive electrode are separated in time, when one LED is driven, the drive voltage is applied to the other LED in the opposite direction. Since is usually smaller than the reverse dielectric strength, the latter LEDs are not driven and can be driven separately even if they share a drive electrode.

〔Example〕

An embodiment of the present invention will be explained with reference to FIGS. 1 to 4. This embodiment shows a case where it is used in an LED printer.
FIG. 1 is a surface view thereof. An n-type array 101 and a p-type array 102 are made adjacent to each other, and the center spacing 103 between them is 1/2 of the write pitch p of the LED printer. The drive electrodes 104 arranged on both sides of these arrays are n-type LEDs arranged in a staggered manner.
105 and the electrodes of the p-type LED 106.

Note that the rotation direction of the photosensitive drum (not shown) of the LED printer is from top to bottom in this figure.

FIG. 2 is a cross-sectional view of the LED array taken along section a107 in FIG. 1. The right side is an n-type array 101, and the left side is a p-type array 102. The base common electrode 201 (base) serves as an anode for an n-type LED and a cathode for a p-type LED, and is grounded. Examples of the composition of each array are shown in Table 2 of the above-mentioned document, n-type is p
GaAs, p-GaAllAs, n-GaAI
J, As, and the p-type is n-GaAs.

It consists of n-GaAsP and p-GaAsP.

The light-emitting portions are pn junctions, as indicated by arrows, and emit light when minority carriers injected there recombine.

A method for driving an LED array according to the present invention will be explained with reference to FIGS. 3 and 4. FIG. 3 shows an embodiment of a driving circuit for a pair of n+P type LEDs. The signal S1 is a drive signal for the n-type LED 303, and in this example, it is Ov when it is on and -5V when it is off. On the other hand, the signal S2 is a drive signal for the p-type LED 304, and in this example, it is Ov when it is on and +5v when it is off. Both signals are provided as signals that do not turn on at the same time. Each signal s1. S2 is input from terminals 301 and 302, respectively, and transistors 305.3
06 is turned on and off. When transistor 305 is turned on, the current controlled by resistor Rl r R3 flows to LE
The light flows through D303 and the LED 303 emits light. At this time L
Since the ED 304 is in the opposite direction, no current flows and no light is emitted. Conversely, when transistor 306 is turned on, resistor RAT
A current controlled by R3 flows through LED 304;
The LED 304 emits light. At this time, the LEDs 303 are in the opposite direction, so that no current flows and no light is emitted.0 or more circuits are required as many as the number of drive electrodes 104 in the array.

FIG. 4 is a drive timing chart of drive signals SL and S2. The signal LCLK is a line synchronization signal for writing line information on the photosensitive drum of the LED printer.
In this example, a square wave with a duty of 50% is used. This is the first
This is because, as shown in the figure, the center spacing 103 of each array is designed to be 172, which is the line pitch. When the signal LCLK is LL HII, the blinking of the LED 303 is controlled by the signal S1, and when it is ``tr L'', the blinking of the LED 304 is controlled by the signal S2.

Since there are as many signals SL and S2 as there are drive electrodes 104, the signals St and S2 shown in this figure are information on two adjacent dots among all the dots in the line. Line No.

1 is when both LEDs do not emit light; No. 2 is when both of them emit light; No. 3 is when only LED 303 emits light; and No. 4 is when only LED 304 emits light.

According to this embodiment, the center spacing 103 of each array in FIG.
(+/25 in pitch) is the signal Sl, 52(7
) This is canceled out by the phase shift, and as a result, it becomes equivalent to blinking all the LEDs on the same line on the photosensitive drum of an LED printer, making it possible to perform high-quality printing without horizontal line fluctuations.

〔Effect of the invention〕

According to the present invention, whereas conventional LED arrays could only be increased in density to about 400 dots/1 nch due to limitations on the size of drive electrodes, it is possible to increase the density to about 800 dots/1 nch, which is twice that of the conventional one, while keeping the electrode size unchanged. This has the effect of realizing a high-density LED array.

[Brief explanation of the drawing]

1 and 2 are a surface view and a sectional view thereof showing an embodiment of the LED array of the present invention, and FIGS. 3 and 4 are diagrams and a drive circuit showing an embodiment of the LED array drive circuit of the present invention. Timing chart FIG. 5 is a surface view showing the configuration of a conventional LED array. +01-n-type LED array, toz...p-type LED array, 103...center spacing, 104...drive electrode, 1
05...N-type LED, 106...P-type LED, 201
...Common electrode, 303- n-type LED, 304=-
p-type LED. 4F, Figure 1 Representative Patent Attorney Tadashi Akimoto Actual Figure + 5V Figure Figure

Claims (1)

[Claims] 1. A plurality of diode pairs each consisting of a pair of n-type and p-type LEDs, one end of which is connected to the same common electrode and the other end of which is connected to the same drive electrode, are arranged in a straight line. An LED array featuring: 2. In the LED array according to claim 1, the n-type L
An LED characterized in that the EDs are arranged along a first straight line, and the p-type LEDs are arranged along a second straight line.
array. 3. In the LED array according to claim 2, the driving time is divided into first and second timings that do not overlap with each other, and the n-type LED is driven at the first timing, and the n-type LED is driven at the first timing, and the A method for driving an LED array, characterized in that the p-type LED is driven at the timing. 4. In the LED driving method according to claim 3, the common electrode is always grounded to have zero potential, and the n
When driving a type LED, a negative voltage whose size is smaller than the reverse withstand voltage of the p-type LED is applied to the drive electrode corresponding to the LED to be driven, and when driving the p-type LED, the driving electrode corresponding to the LED to be driven is applied. A method for driving an LED array, comprising applying a positive voltage to an electrode, the size of which is smaller than the reverse withstand voltage of an n-type LED.