JPH11277795A - Led print head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a print head conform to wide printing by alternately arranging a first and a second light-emitting groups in a serpentine shape on a long substrate, and alternately holding a plurality of rod-shaped lenses corresponding to the first and second light-emitting groups by a holding member in a staggered shape. SOLUTION: A substrate unit 2 has a first, a second light-emitting groups 22, 23 arranged alternately in a staggered shape in a longitudinal direction of a long circuit board 21 of ceramic or the like. Each of the first, second light-emitting groups has a plurality of LED arrays 24 arranged in a scan direction and a plurality of driving ICs 25 arranged in the scan direction to pair the LED arrays 24 on the circuit board 21. A pair of holding members 32, 33 hold rod-shaped lenses to position nearly right over the first, second light- emitting groups 22, 23 along the arrangement of the LED arrays 24. This print head is thus adapted to wide printing and improved in printing accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an LED print head suitable for a print head such as an optical printer.

[0002]

2. Description of the Related Art An LED print head of this type includes an LED array having a plurality of LED light emitting units and an I / O array for driving the LED array.
A plurality of Cs are arranged on the substrate along the longitudinal direction of the substrate, and a bar-shaped lens such as a SELFOC lens (trade name) longer than the arrangement length of the LED array is disposed above the LED array via a holder. keeping. Although LED print heads of various lengths adapted to the size of the recording paper (A4 to A0) have been developed, the rod-shaped lens is required to maintain the print quality. Regardless, one seamless rod-shaped lens is used. However, a rod-shaped lens becomes expensive due to a sharp increase in manufacturing cost as its dimension becomes longer. For example, A
A rod lens conforming to the 0 size is 10 times or more more expensive than a rod lens conforming to the A4 size. Therefore, as the length of the head increases, the ratio of the rod-shaped lens in the cost increases.

Further, as the length of the print head becomes longer, the difference in the coefficient of thermal expansion between the rod-shaped lens and the holder or radiator supporting the rod-shaped lens becomes easier to accumulate. It is easy to occur. Printing accuracy is likely to be reduced due to the warpage of the lens.

Therefore, as shown in, for example, Japanese Patent Application Laid-Open No. 7-61035, a general-purpose size of about A4 size and A0 size using a plurality of existing LED print heads.
It has been proposed to assemble print heads as wide as possible. However, in such a configuration, if attention is paid to the rod-shaped lens, a holder for assembling into a wide print head is required in addition to a lens holder for assembling into a general-purpose print head. The number of parts, including constituent parts, tends to increase, which tends to increase the size of the shape and increase the number of assembly steps. Also, after making optical adjustments for each general-purpose LED printhead, and after assembling them,
It is necessary to perform overall adjustment, and the number of optical adjustment work steps is likely to increase. Furthermore, it is necessary to arrange the LED arrays with high accuracy so that the pitch of the LED light emitting portions is kept constant even at the joint thereof. Since the substrate to be placed will be divided into multiple,
It is difficult to accurately maintain the pitch of the light emitting units between the LED arrays, and this tends to cause a reduction in printing accuracy.

[0005]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an LED print head suitable for wide printing. Also, such a print head,
An object is to provide an inexpensive assembly and optical adjustment with good workability. Another object is to maintain good printing accuracy of the print head.

[0006]

According to the present invention, there is provided an LED print head in which first and second light emitting groups formed by arranging a plurality of LED arrays are alternately arranged in a staggered manner on a long substrate. A plurality of rod-shaped lenses corresponding to the first and second light-emitting groups are alternately held in a staggered manner by a holding member.

Further, the LED print head of the present invention comprises:
A plurality of LED arrays and driving ICs for the first and second light emitting groups are arranged alternately in a zigzag pattern on a long substrate and correspond to the first and second light emitting groups. A plurality of rod-shaped lenses are alternately held in a staggered manner by holding members.

In the above configuration, a plurality of driving ICs for driving the LED array are arranged in a line along the longitudinal direction of the substrate, and the plurality of LED arrays forming the first and second light emitting groups are arranged. , Can be distributed on both sides of the row of driving ICs. In addition, the LE
The D array can be configured by integrally including a plurality of LED light emitting units arranged and arranged.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an LE according to an embodiment of the present invention.
FIG. 3A is a plan view, FIG. 3B is a bb sectional view thereof, and FIG. 3C is a cc sectional view thereof. FIG. 2 is a plan view showing a schematic configuration of the board unit 2 of the embodiment.

As shown in FIGS. 1B and 1C, in the LED print head 1, a substrate unit 2 and an optical unit 3 are arranged on a heat radiating unit 4 also serving as a support member, and the substrate unit 2 is attached to the optical unit 3 And the heat radiation unit 4.

As shown in FIG. 2, the board unit 2 is provided on a long (corresponding to A0 or A1 size) circuit board 21 made of ceramic or glass epoxy, on which first and second light emitting groups 22 are formed. , 23 are alternately arranged in a staggered manner along the longitudinal direction of the substrate 21 (hereinafter referred to as a scanning direction).

Each of the first and second light emitting groups 22 and 23 has a plurality of LED arrays 2 arranged in the scanning direction.
4 and a plurality of driving ICs 25 arranged along the scanning direction so as to form a pair with the LED array 24.
These driving ICs 25 are arranged in a row along the scanning direction, and an LED array 24 belonging to the first light emitting group 22 and an LED array belonging to the second light emitting group 23 are provided on both sides of the row of the driving ICs 25. 24 are arranged alternately in a staggered pattern.

As described above, one substrate 21 is provided with a plurality of LEs.
Since the D array 24 and the plurality of driving ICs 25 are arranged, when the arrangement is performed by using an automatic bonding apparatus which is usually used, the absolute coordinates set once can be used for the positioning, and divided into a plurality of substrates. The LED array 24 and the driving IC 25
Can keep the position accuracy extremely high. In particular, since the driving ICs 25 are arranged in a line, the operability and arrangement accuracy thereof can be improved.

As shown in an enlarged manner in FIG. 2, the LED array 24 has a plurality of LED light emitting portions 24a formed on a surface of a compound semiconductor substrate by, for example, a selective diffusion method and the like, and these LED light emitting portions 24a are arranged in a predetermined manner. They are arranged in a line at a pitch along the scanning direction (the longitudinal direction of the array 24). Each of the LED arrays 24 is connected between the LED arrays 24 belonging to the same light emitting group and between the LED arrays 24 belonging to different light emitting groups.
The substrate 2 is arranged such that the arrangement pitch of the D light emitting portions 24a is maintained.
1 and fixed. Some LED arrays 24 belong to different light emitting groups.
The light emitting units 24a may be arranged so as to overlap in the scanning direction while maintaining an interval in the width direction of the substrate 21 (hereinafter, referred to as a sub-scanning direction).

On the surface of the LED array 24, LED light emitting portions 24a are arranged offset to one side, and individual electrodes 24b for wire bonding connected to the LED light emitting portions 24a are arranged offset to the other side. I have.

Although the driving ICs 25 are arranged in one line, as shown in an enlarged manner in FIG. 2, the driving ICs 25 belonging to the first light emitting group 22 and the second
The driving ICs 25 belonging to the LED array 24 are arranged so as to face each other, and their output terminal portions 25a face the individual electrodes 24b of the LED array 24. The output terminal portion 25a and the individual electrode 24b are connected by a wire bond wire (not shown).

As shown in FIG. 1, the optical unit 3 includes a plurality of rod-shaped lenses 31 such as a selfoc lens (trade name) and a pair of holders 32 and 33 along a scanning direction.
(Holding member). Rod lens 31
Is detachably fixed to the pair of holders 32 and 33, but a detachable adhesive, a double-sided adhesive tape, or the like may be used for the fixing. And this optical unit 3
It is detachably fixed to the heat radiating unit 4 by screws 34 or the like. The rod-shaped lens 31 is formed to be slightly longer than the length of the first and second light-emitting groups so that a part thereof overlaps in the scanning direction, and the first and second light-emitting groups are formed by holders 32 and 33. 22 and 23 are alternately held in a staggered manner. That is, each of the rod-shaped lenses 31 is held so as to be positioned almost directly above the LED arrays 24 of the first and second light-emitting groups 22 and 23.

As described above, since the rod-shaped lenses 31 are sufficiently shorter than the length of the print head 1 and are arranged in a staggered manner, the rod-shaped lenses 31 are caused by the difference in the coefficient of thermal expansion between the holders 32 and 33 and the like. Even if the expansion and contraction occurs, the expansion and contraction
It can be absorbed in one unit, and the accumulation of expansion and contraction as in the case of using one rod-shaped lens can be prevented.

The heat dissipating unit 4 is made of a long metal having good thermal conductivity such as aluminum, and has a flat surface on the upper surface for disposing the substrate unit 2 and a heat dissipating fin on the lower surface. Is formed.

In the above configuration, the corresponding LED is driven by the driving IC 25 belonging to the first light emitting group 22.
When the array 24 is driven, the light emitted from the LED light-emitting unit 24 a receives a recording object (photosensitive drum) via a rod-shaped lens 31 located above the first light-emitting group 22.
Is irradiated. Similarly, the driving IC 25 belonging to the second light emitting group 23 causes the corresponding LED array 24
Is driven, the light emitted from the LED light emitting section 24a is irradiated on the recording object (photosensitive drum) via the rod-shaped lens 31 located above the second light emitting group 23.

Here, the first and second light emitting groups 22,
Since the 23 LED arrays 24 are arranged at intervals in the sub-scanning direction of the substrate 21, when the first and second light-emitting groups 22, 23 are simultaneously driven, a step in irradiation occurs in the scanning direction. Therefore, this LED print head 1
Is preferably driven by a dynamic (time-division) driving method. Also, the first and second light emitting groups 2
It is desirable to provide a processing circuit for processing data corresponding to the sub-scanning directions 2 and 23 into appropriate ones according to the interval in the sub-scanning direction, inside or outside the LED print head 1.

The substrate unit 2 is based on a conventional structure in which an LED array and a driving IC are arranged in the scanning direction at a constant interval in the sub-scanning direction. It can also be configured as shown. That is, while maintaining the same arrangement of the LED arrays 24 and the driving ICs 25 in the first and second light emitting groups 26 and 27, the first and second light emitting groups 26 and 27 are moved in the sub-scanning direction. It is also possible to adopt a form in which they are alternately arranged in a staggered manner at predetermined intervals.

As described above, the LED print head 1 comprises the optical unit 3 using a plurality of short rod lenses 31 which can be obtained at low cost.
Compared to the case where a rod-shaped lens having the same length as the print head 1 is used, the cost of the optical unit 3 can be reduced, and the distortion of the lens 31 can be suppressed to increase the optical accuracy. Further, the number of components for holding the lens 31 can be reduced, so that the number of components can be reduced and the assembling workability can be improved.

[0024]

As described above, according to the present invention, since a plurality of bar-shaped lenses arranged in a staggered manner are held by the holding member, an LED print head suitable for wide printing can be assembled and optically manufactured at low cost. It is possible to provide good adjustment workability. In particular, when arranging light emitting groups in a staggered manner corresponding to a plurality of rod-shaped lenses,
One LED array or driving IC that constitutes a light emitting group
Since they are arranged on one substrate, the alignment accuracy of the LED array and the driving IC can be kept extremely high, and the printing accuracy can be improved, as compared with the conventional system using a plurality of substrates corresponding to the light emitting groups. Can be.

[Brief description of the drawings]

1A and 1B show an embodiment of an LED print head according to the present invention, in which FIG. 1A is a plan view, FIG.
(C) is a cc cross-sectional view thereof.

FIG. 2 is a plan view showing a schematic configuration of the board unit of the embodiment.

FIG. 3 is a plan view schematically showing another configuration example of the board unit of the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 LED print head 2 Substrate unit 21 Circuit board 22 1st light emission group 23 2nd light emission group 24 LED array 25 Drive IC 3 Optical unit 31 Bar lens 32 Holder 33 Holder 4 Heat dissipation unit

Claims (4)

[Claims] 1. A first and a second light emitting group comprising a plurality of LED arrays arranged alternately in a zigzag pattern on a long substrate and corresponding to the first and the second light emitting groups. An LED print head, wherein a plurality of rod-shaped lenses are alternately held in a staggered manner by holding members. 2. A method according to claim 1, wherein the first and second light-emitting groups each having a plurality of LED arrays and their driving ICs are arranged alternately in a zigzag pattern on a long substrate. L, wherein a plurality of rod-shaped lenses corresponding to the light-emitting groups are alternately held in a staggered manner by a holding member.
ED print head. 3. A plurality of driving ICs for driving the LED array are arranged in a line along a longitudinal direction of the substrate, and a plurality of LED arrays constituting first and second light emitting groups are arranged. 3. The LED print head according to claim 1, wherein said LED print head is arranged on both sides of said row of drive ICs. 4. The LED print head according to claim 1, wherein the LED array integrally includes a plurality of LED light emitting units arranged and arranged.