JPH10151795A - Led print head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve image quality, reduce a chip size of a driver IC and lower costs of an LED print head. SOLUTION: The LED print head has a substrate 11, a first LED array 24 on the substrate 11 which has a plurality of light-emitting parts 26 arranged with a predetermined pitch and an electrode pattern, a second LED array 25 on the first LED array 24 which has a plurality of light-emitting parts 27 via the equal pitch as the predetermined pitch and an electrode pattern, and a driver IC 12 connected to independent electrodes forming the electrode patterns of the first and second LED arrays 24, 25. The light-emitting parts 26 of the first LED array 24 and light-emitting parts 27 of the second LED array 25 are shifted every half pitch to send out light from a face at right angles to a face where the electrode pattern is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an LED print head used as an exposure device for an electrophotographic printer.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic printer, an electrostatic latent image is formed by exposing the surface of a photosensitive drum uniformly and uniformly charged by an exposure device, and developing the electrostatic latent image. Thus, a toner image is formed, and the toner image is transferred and fixed on a sheet. For example, an LED print head is used as the exposure device,
An electrostatic latent image is formed by selectively causing the light emitting portion of the ED print head to emit light in accordance with the print data.

FIG. 2 is a perspective view of a conventional LED print head. In the figure, 11 is a substrate, 12 is the substrate 11
Driver ICs arranged in a line on the
Reference numeral 3 denotes an LED array disposed on the substrate 11 in parallel with the driver IC 12;
Are a plurality of light-emitting portions formed in the light-emitting device. The driver IC1
The LED array 13 is connected to the LED array 13 by wire bonding 16, and the driver IC 12 drives the LED array 13 according to the print data to selectively emit light from each light emitting unit 14. The light from each light emitting section 14 is sent out in a direction perpendicular to the surface of the LED array 13 on which an electrode pattern (not shown) is formed.

The number of the LED arrays 13 and each LED
The number of light emitting portions 14 in the array 13 depends on the size and resolution of the LED printhead. For example, A4
In the case of an LED print head capable of printing on a paper (not shown) at a resolution of 600 [dpi], about 40 LED arrays 13 are mounted, and each LED array 13 emits 128 light. The part 14 is formed.

[0005]

However, in the above-mentioned conventional LED print head, it is necessary to arrange the LED arrays 13 on the substrate 11 adjacent to each other.
Each light emitting unit 1 is located at a portion where each LED array 13 is adjacent.
The light emission characteristics of No. 4 decrease, and the image quality deteriorates. FIG. 3 is a diagram showing the arrangement of a conventional LED array.

In the figure, 13 is an LED array, 14 is a light emitting section, and 18 is an end of the LED array 13. Each light emitting unit 14 is disposed at a pitch w1 corresponding to the resolution of the LED print head.
[Dpi] LED print head, pitch w1
Is 42.3 [μm]. Further, each of the light emitting units 14
Is formed in a photolithography process when manufacturing the LED array 13, the pitch w1 can be set with extremely high precision.

On the other hand, the interval w2 between the light emitting portions 14 in the portion where the LED arrays 13 are adjacent to each other
It is determined by the distance S between the arrays 13 and the distance L between the end portion 18 of each LED array 13 and the light emitting portion 14 closest to the end portion 18. By the way, the distance L is determined by a dimension when the LED array 13 is cut out from a wafer (not shown). For example, when the light reaches the light emitting unit 14, the light emitting unit 14
The light-emitting characteristics of the device are degraded.

Further, it is necessary to secure the distance S of several microns so that the adjacent LED arrays 13 do not contact each other. Therefore, the interval w2 cannot be made sufficiently small. Particularly, when manufacturing an LED print head having a high resolution, the interval w2 becomes longer than the pitch w1, and the LED arrays 13 of the printed image are adjacent to each other. White streaks are formed in the portions where the LED print head is formed, and the image quality of the LED print head is degraded.

Further, when manufacturing an LED print head having a high resolution, the connection density between each light emitting section 14 and the driver IC 12 (FIG. 2) becomes high, so that a short circuit occurs between the wires of the wire bonding 16. In some cases, the yield of the wire bonding 16 is reduced accordingly, and the cost of the LED print head is increased.

Further, in an LED print head having a high resolution, the number of light emitting portions 14 is large. For example, an LED print head having a resolution of 1200 [dpi] is twice as large as an LED print head having a resolution of 600 [dpi]. The light emitting unit 14 is provided. In this case, it is necessary to perform control for selectively causing each of the light emitting units 14 to emit light.
It is necessary to increase the circuit scale of the driver IC 12
Not only increases the chip size of the
The cost of the D print head increases.

The present invention solves the above-mentioned problems of the conventional LED print head, improves the image quality, reduces the chip size of the driver IC, and reduces the cost. It is an object to provide a print head.

[0012]

For this purpose, the L of the present invention is used.
In an ED print head, a first LED formed with a substrate, a plurality of light emitting portions arranged on the substrate and arranged at a predetermined pitch, and an electrode pattern connected to the light emitting portion is formed. An array, a plurality of light emitting units arranged on the first LED array, arranged at a pitch equal to the pitch, and a second LED formed with an electrode pattern connected to the light emitting unit An array and a driver IC connected to each individual electrode forming each electrode pattern of the first and second LED arrays and driving the first and second LED arrays.

The light-emitting portions of the first LED array and the light-emitting portions of the second LED array are arranged so as to be shifted from each other by a half pitch, and are perpendicular to the surface on which the electrode patterns are formed. Send light out of the surface.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a perspective view of an LED print head according to a first embodiment of the present invention, FIG. 4 is a sectional view taken along line XX of FIG. 1, and FIG. 5 is an arrangement of an LED array according to the first embodiment of the present invention. It is a state diagram.

In the figure, 11 is a substrate, 12 is the substrate 1
A plurality of driver ICs arranged in a line on
Reference numeral 23 denotes an LED array unit disposed on the substrate 11 in parallel with the driver IC 12. The LED array unit 23 turns the first LED array 24 and the second LED array 25 upside down, and
The LED arrays 24 and 25 are mounted together with their front surfaces in contact with each other, and are mounted with the back surface of the first LED array 24 in contact with the substrate 11. Reference numeral 26 denotes each first LED array 2
4, a plurality of light-emitting portions 27 arranged at a pitch p,
Are arranged in the LED array 25 at a pitch p, and each of the light emitting units 26 and 27 is half a pitch p from each other.
/ 2 offset from each other.

In this case, each pitch p of the light emitting portions 26 and 27 is
The resolution of the LED print head can be doubled without reducing the size of the LED print head. Further, since the pitch p of the light emitting portions 26 and 27 can be increased without lowering the resolution of the LED print head, the first and second pitches can be increased.
The distance L between each end of the LED arrays 24 and 25 and the light emitting units 26 and 27 closest to the end can be increased.

Therefore, the first and second LED arrays 2
When cutting out the wafers 4 and 25 from a wafer (not shown), no damage is applied to the light emitting units 26 and 27, and the cracks and hooks generated by the cutting do not reach the light emitting units 26 and 27. A second LED array 24,
25 light emitting characteristics can be improved. Further, the interval between the light emitting units 26 between the first LED arrays 24 or the interval between the light emitting units 27 between the second LED arrays 25 can be sufficiently reduced.
White streaks do not occur between the first LED arrays 24 or between the second LED arrays 25 of the printed image, and the image quality of the LED print head can be improved. Moreover, in this case, it is not necessary to shorten the distance S between the first LED arrays 24.

The driver IC 12 drives the first and second LED arrays 24 and 25 according to print data,
Each of the light emitting units 26 and 27 selectively emits light. To this end, an electrode pattern 35 made of a P-side electrode is formed on the front surface of the first LED array 24, and a common electrode (not shown) made of an N-side electrode is formed on the back surface. In addition, the second
An electrode pattern 36 made of a P-side electrode is formed on the front surface of the LED array 25, and a common electrode (not shown) made of an N-side electrode is formed on the back surface. And the driver IC1
2 and the electrode pattern 35 of the first LED array 24 are connected to the driver I
C12 and the common electrode of the second LED array 25 are connected by one common electrode wire 32, respectively. Further, the substrate 11 and the common electrode of the first LED array 24 are directly connected. In addition, 37 is a bump.

The light emitting portions 26 and 27 are sent out from the end surfaces of the first and second LED arrays 24 and 25, that is, the surfaces perpendicular to the surfaces on which the electrode patterns 35 and 36 are formed. It is. Next, the electrode patterns 35 and 36 will be described. FIG. 6 is a plan view of a first LED array according to the first embodiment of the present invention, FIG. 7 is a sectional view taken along line YY of FIG. 6, and FIG. 8 is a second view of the second embodiment according to the first embodiment of the present invention. It is a top view of an LED array.

In FIG. 6, reference numeral 24 denotes a first LED array, 35 denotes an electrode pattern formed on the surface of the first LED array 24, and the electrode pattern 35 is connected to each wire bonding 31 (FIG. 4). Connected driver IC
The connection pad 51, the individual electrode 52, the LED array connection pad 53 connected to the driver IC connection pad 51 via the individual electrode 52, and the LED array connection pad 53 and each light emitting unit 26. Individual electrode 5 to be connected
Consists of four.

The electrode pattern 35 includes a P-side electrode 58 formed on one surface of an N-side substrate 56 via an insulating film 57, as shown in FIG.
A common electrode composed of an N-side electrode 59 is formed on the other surface of the substrate. The light emitting section 26 is formed of a P-side diffusion layer formed on the N-side substrate 56 by selective diffusion. FIG.
In the figure, 25 is a second LED array, 36 is an electrode pattern formed on the surface of the second LED array 25, and the electrode pattern 36 is a LED array connection pad 61 and each LED array connection pad. It comprises an individual electrode 62 for connecting the light emitting portion 27 to the light emitting portion 61. In this case, each of the light emitting units 26 and each of the light emitting units 27 have a half pitch p.
/ 2 (FIG. 5), the individual electrodes 62 extend obliquely between the LED array connection pad 61 and the light emitting section 27.

The LED array connection pad 6
A bump 37 is formed on 1, and the LED array connection pad 61 and the LED array connection pad 53 are connected via the bump 37. Therefore, the individual electrode 52 is common to the first and second LED arrays 24 and 25 and is connected to the driver IC 12 via each driver IC connection pad 51 and each wire bonding 31.

That is, each wire bonding 31 extending from the driver IC 12 is connected to each light emitting section 26 via the driver IC connection pad 51, the individual electrode 52, the LED array connection pad 53 and the individual electrode 54, and the driver IC connection pad 51, individual electrode 52,
The light emitting units 27 are connected to the LED array connection pads 53, the bumps 37, the LED array connection pads 61, and the individual electrodes 62. In this case, the individual electrodes 52 connected to the light-emitting portions 26 and 27 are common, but the first LED
The P-side electrode 58 formed on the back surface of the array 24 and the common electrode (not shown) formed on the back surface of the second LED array 25 are independently connected to a ground (not shown). Therefore, light can be emitted with a time difference between the light emitting unit 26 and the light emitting unit 27.

As a result, even when an LED print head having a high resolution is manufactured, the connection density between each of the light emitting portions 26 and 27 and the driver IC 12 can be reduced to half that of the conventional LED print head. In addition, a short circuit does not occur between the wires of the wire bonding 31, the yield of the wire bonding 31 is increased correspondingly, and the cost of the LED print head can be reduced.

Further, since it is not necessary to increase the circuit scale of the driver IC 12 in order to control the light emitting sections 26 and 27 to selectively emit light, the driver IC 12
Not only can reduce the chip size of
The cost of the LED print head can be reduced. Next, the circuit of the LED print head having the above configuration will be described.

FIG. 9 is a circuit diagram of the LED print head according to the first embodiment of the present invention. In the figure, 1
Reference numeral 2 denotes a driver IC, and the driver IC 12 includes a shift register 67, a latch circuit 68, an AND circuit 69, and a drive circuit 70. Further, the driving circuit 70, the respective light emitting units 26 of the first LED array 24 and the second LE
Each light emitting unit 27 of the D array 25 is connected to the wire bonding 3
1 connected. Then, each light emitting unit 26 is mounted on the substrate 1
Each light emitting unit 27 is connected to a switch 66 via an electrode wire 32 via a wiring 65 on 1 (FIG. 1). Therefore, by switching the switch 66, the electrode wire 32 or the wiring 65 is selectively connected to a ground (not shown), and each light emitting unit 26 or each light emitting unit 27 is connected.
Can emit light.

In the LED print head having the above-described configuration, the control unit (not shown) sends the first L to the driver IC 12.
When the print data DATA for driving the ED array 24 is sent, the switch 66 is switched, the electrode wire 32 is connected to the ground, and the print data DATA is sequentially sent to the shift register 67 in synchronization with the clock signal CLK. Is entered. And the shift register 6
7, when one line of print data DATA is input,
The latch signal LATCH is sent from the control unit to the latch circuit 68, and the print data DA
TA is latched by the latch circuit 68.

When the strobe signal STB is input from the control unit to the AND circuit 69, the print data D
A current is supplied from the driver IC 12 to each light emitting unit 26 according to the ATA, and the light emitting unit 26 emits light. In this case, since the wiring 65 is not connected to the ground, no current is supplied to each light emitting unit 27, and the light emitting unit 27 is not allowed to emit light.

Next, the control unit sends the driver IC 12 a second
Data DAT for driving the LED array 25 of FIG.
When A is sent, the switch 66 is switched, the wiring 65 is connected to the ground, and the print data DATA is sequentially input to the shift register 67 in synchronization with the clock signal CLK. Then, the shift register 67
When the print data DATA for one line is input to the shift register 67, the control unit sends a latch signal LATCH to the latch circuit 68, and the print data DAT input to the shift register 67.
A is latched by the latch circuit 68.

When the strobe signal STB is input from the control unit to the AND circuit 69, the print data D
A current is supplied from the driver IC 12 to each light emitting unit 27 according to the ATA, and the light emitting unit 27 emits light. In this case, since the electrode wire 32 is not connected to the ground, no current is supplied to each light emitting unit 26, and the light emitting unit 26 does not emit light.

Next, a second embodiment of the present invention will be described. FIG. 10 is a perspective view of an LED print head according to a second embodiment of the present invention, and FIG.
It is a Z sectional view. The components having the same structure as the first embodiment are given the same reference numerals, and the description thereof is omitted. In this case, the LED array unit 23 turns the first LED array 101 and the second LED array 102 upside down from each other, and the first and second LEDs
The first and second arrays 101 and 102 are formed by joining the respective front surfaces thereof, and are mounted with the back surface of the first LED array 101 in contact with the substrate 11.

An electrode pattern 136 made of a P-side electrode is formed on the front surface of the first LED array 101, and a common electrode (not shown) made of an N-side electrode is formed on the back surface. Also, the surface of the second LED array 102 has P
An electrode pattern 135 composed of a side electrode and a common electrode (not shown) composed of an N-side electrode are formed on the back surface. The driver IC 12 and the second LED array 10
The two electrode patterns 135 are connected by bumps 71, and the driver IC 12 and the common electrode of the second LED array 102 are connected by one common electrode wire 72. Further, the substrate 11 and the first LED array 101
Is directly connected to the common electrode.

Accordingly, the driver IC 12 is connected to the light emitting section 126 through the bump 71 and the individual electrode (not shown) forming the electrode pattern 135, and the bump 71, the individual electrode, the bump 137, and the electrode pattern 136 are formed. Are connected to the light emitting section 127 via an individual electrode (not shown). It should be noted that the present invention is not limited to the above-described embodiment, but can be variously modified based on the gist of the present invention, and they are not excluded from the scope of the present invention.

[0034]

As described above in detail, according to the present invention, in a LED print head, a substrate and a plurality of light emitting units arranged on the substrate and arranged at a predetermined pitch. And a first LED array on which an electrode pattern connected to the light emitting unit is formed, and the first LED
A second LED array having a plurality of light emitting units disposed on the array and arranged at a pitch equal to the pitch, and an electrode pattern connected to the light emitting units; A driver IC connected to each individual electrode forming each electrode pattern of the two LED arrays and driving the first and second LED arrays;

The light-emitting portions of the first LED array and the light-emitting portions of the second LED array are arranged so as to be shifted from each other by a half pitch, and are perpendicular to the surface on which the electrode patterns are formed. Send light out of the surface. In this case, the resolution of the LED print head can be doubled without reducing the pitch of each light emitting unit of the first and second LED arrays.

Accordingly, the number of light-emitting portions can be reduced, so that it is not necessary to increase the circuit scale of the driver IC. As a result, not only the chip size of the driver IC can be reduced, but also the cost of the LED print head can be reduced. In addition, without lowering the resolution of the LED print head, the first and second LEs can be used.
Since the pitch of each light emitting unit of the D array can be increased, the distance between the end of each of the first and second LED arrays and each light emitting unit closest to the end can be increased.

Therefore, when the first and second LED arrays are cut out from the wafer, no damage is applied to each light-emitting portion, and cracks and cracks caused by the cutting do not reach each light-emitting portion. The first and second LEs
The light emission characteristics of the D array can be improved. Further, the interval between the light emitting units between the respective first LED arrays or the interval between the respective light emitting units between the respective second LED arrays can be sufficiently reduced. Between the first LED arrays or each second L
There is no white streak between the ED arrays, and the image quality of the LED print head can be improved.

[Brief description of the drawings]

FIG. 1 is a perspective view of an LED print head according to a first embodiment of the present invention.

FIG. 2 is a perspective view of a conventional LED print head.

FIG. 3 is a view showing an arrangement state of a conventional LED array.

FIG. 4 is a sectional view taken along line XX of FIG. 1;

FIG. 5 is an arrangement state diagram of an LED array according to the first embodiment of the present invention.

FIG. 6 shows a first LE in the first embodiment of the present invention.
It is a top view of a D array.

FIG. 7 is a sectional view taken along line YY of FIG. 6;

FIG. 8 shows a second LE in the first embodiment of the present invention.
It is a top view of a D array.

FIG. 9 is a circuit diagram of the LED print head according to the first embodiment of the present invention.

FIG. 10 is a perspective view of an LED print head according to a second embodiment of the present invention.

11 is a sectional view taken along the line ZZ of FIG.

[Explanation of symbols]

 11 Substrate 12 Driver IC 24, 101 First LED Array 25, 102 Second LED Array 26, 27, 126, 127 Light Emitting Part 35, 36, 135, 136 Electrode Pattern 52, 54, 62 Individual Electrode P Pitch p / 2 half pitch

Claims (3)

[Claims] 1. A (a) substrate, and (b) a plurality of light emitting portions arranged on the substrate and arranged at a predetermined pitch, and an electrode pattern connected to the light emitting portion are formed. A first LED array, and (c) a plurality of light emitting units arranged on the first LED array and arranged at a pitch equal to the pitch, and an electrode pattern connected to the light emitting unit A second LED array formed with
(D) first and second LEDs connected to each individual electrode forming each electrode pattern of the first and second LED arrays;
A driver IC for driving the array,
(E) Each light emitting portion of the first LED array and each light emitting portion of the second LED array are arranged so as to be shifted from each other by a half pitch, and a surface perpendicular to a surface on which each electrode pattern is formed. An LED print head that emits light from a LED. 2. The LED print head according to claim 1, wherein each individual electrode in the electrode pattern of the first LED array and each individual electrode in the electrode pattern of the second LED array are connected to each other. 3. The LED print according to claim 1, wherein the common electrode formed on the first LED array and the common electrode formed on the second LED array are connected to the ground independently of each other. head.