JPH0655774A - Optical printer head - Google Patents

Abstract

PURPOSE:To obtain a small-size, light-weight optical printing head capable of realizing high-density, high-quality printing. CONSTITUTION:A title head comprises a long substrate 1 with a plurality of light emitting diode array elements 6-1, 6-2,... aligned and bonded on its surface; a lens array 4 disposed on an optical axis of a light emitted by the light emitting diode array elements; an enclosure 3 loading and including the substrate and the lens array; and a substrate fixing mechanism 9 connecting the substrate to said enclosure and making the enclosure movable in a main scanning direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical printer head using a light emitting diode array.

[0002]

2. Description of the Related Art There is a printing head having an optical print head using a light emitting diode array. As an example thereof, for example, a plurality of light emitting diode array elements are arranged on a substrate, and a short focus lens array (hereinafter referred to as a lens array) is combined to form an optical print head, and light from the head is projected onto a surface of a photoreceptor. The technique of exposing is disclosed in JP-A-56-30154.

In FIG. 9 for explaining the main part of a conventional optical printer head, reference numeral 1 is a long substrate, reference numeral 2 is a base of an envelope, reference numeral 3 is a lens array fixing jig, and reference numeral 4 is a short focus lens. Array (also simply called lens array), reference numeral 6
Is a light emitting diode array element, reference numeral 7 is a drive circuit element,
Reference numeral 8 indicates a bonding wire, and reference numeral 9 indicates a board fixing screw. The lens array fixing jig 3 constitutes a part of the envelope.

[0004]

In the optical printer head, the light emitting diode array element 6 and its drive circuit element 7 generate heat during lighting operation, and this heat is transmitted to the substrate 1 and the lens array fixing jig 3. Raise the temperature of.

The lens array fixing jig 3 is fixed to the substrate 1. However, since the thermal expansion coefficient is different due to the difference in the materials of both, the substrate is deformed such as warped due to this temperature rise. When this deformation occurs, the quality of the image formed on the photoreceptor is adversely affected.

The lens array 4 has a shallow depth of field, and the distance between the light source and the surface of the photoconductor (so-called object-to-object distance) is a conjugate length (T).
It must be set correctly within C), and its allowable value is extremely small.

Incidentally, regarding such alignment in an optical printer head using a surface emitting type light emitting diode, Japanese Patent Laid-Open Publication No. 59-170816 and Japanese Laid-Open Patent Publication No. 62-170816 disclose.
However, the allowable value is ± 0.
It is small, around 2 mm.

The reason why the allowable value is reduced in this way is that
This is because it is necessary to reduce fluctuations after attachment adjustment, especially fluctuations in optical position due to thermal expansion and deformation of the substrate due to rise in substrate temperature due to driving of the light emitting diode array.

For example, a description will be given of the fluctuation of the optical position due to the thermal expansion of the substrate of the optical printer head for A3 format.
As shown in FIG. 10, the plurality of light emitting diode array elements and the substrate on which the driving elements are mounted and fixed are kept at room temperature or below, and the central portion and both end portions of the envelope are arranged in the enclosure while performing optical adjustment with the lens array. Fixed in place.

For example, the length of the substrate 1 is about 320 mm. When this light emitting diode is driven to light, the temperature of the substrate rises to about 90 ° C, and the temperature in the vicinity of the substrate installation position of the envelope reaches about 80 ° C.

In this case, the substrate 1 is warped as shown in FIG. 11 due to the difference in expansion amount between the substrate and the envelope due to thermal expansion. The amount of this warp can amount to several mm.

[0012] As an example of this countermeasure, US Pat.
In No. 27, as shown in FIG. 12, the envelope of the optical print head is configured by also serving as a flat heat dissipation plate, and the substrate on which the light emitting diode is mounted is fixed to this with an adhesive or the like. , A technology has been introduced in which a lens array is fixed to the heat dissipation plate to reduce the influence of heat and to maintain the optical distance once adjusted.

However, this is still not sufficient, and it is necessary to give the envelope sufficient rigidity to prevent the substrate from warping and to firmly fix the substrate to the envelope. However, in this case, the envelope becomes large and a large radiator needs to be attached, which eventually leads to an increase in size and weight of the print head, and a large amount of solid fixing. This requires holding parts and a strong adhesive, which complicates the fixing work and increases the manufacturing cost. This is a major obstacle to downsizing and cost reduction of the optical printer.

In an optical printer head which prioritizes miniaturization and weight reduction of the head without any measures, it is not possible to take sufficient rigidity to withstand deformation due to thermal expansion, and to prevent warpage of the substrate during light emission drive. Therefore, a lens array having a shallow depth of field cannot be used. Therefore, it is difficult to increase the image density, that is, to reduce the size of pixels.

On the other hand, in the optical printer head using the edge emitting type light emitting diode array (see FIG. 13),
The warp of the substrate causes the emission shape to be curved in the main scanning direction.

In an optical printer head using such an edge emitting type light emitting diode array, the optical position is adjusted at room temperature as shown in FIG. 14 and linearly formed on the photosensitive member as shown by the broken line. The light emission shape is projected, and when the optical printer head performs continuous light emission or the like and the temperature of the substrate rises, the substrate warps.

Then, as shown in FIG. 15, the projected image on the photosensitive member is curved according to the warp of the substrate. That is,
The projected image on the photoconductor, which is linear before the temperature rises as shown by the one-dot chain line in the figure, becomes curved following the warp of the substrate as shown by the broken line after the temperature rises.

Such a curvature of the projected image causes distortion of the print output of the optical printer. Therefore, even in the optical printer using the edge emitting type light emitting diode array, if the image quality is prioritized, Similar to the optical printer head using the surface emitting type light emitting diode array, it is necessary to increase the rigidity of the envelope, that is, to increase the size and weight of the printer head.

Therefore, an object of the present invention is to provide a compact and lightweight optical print head capable of realizing high density and high quality printing.

[0020]

In order to achieve the above object, the present invention has any one of the following configurations.

(1). A long substrate in which a plurality of light emitting diode array elements are aligned and mounted on the surface and fixed, a lens array arranged on the light emission optical axis of the light emitting diode array element, and the substrate and the lens array are stacked and contained. An envelope is provided, and a substrate fixing mechanism that connects the substrate to the envelope and that moves the envelope in the main scanning direction is provided (claim 1).

(2). In (1), the substrate fixing mechanism has a coil spring that constantly pulls the substrate toward both ends of the substrate in the main scanning direction (claim 2).

(3). In (1), a fluid heat transfer material is sandwiched between the long substrate and the envelope (claim 3).

[0024]

The expansion of the substrate due to the thermal expansion is absorbed by the substrate fixing mechanism.

[0025]

【Example】

Example 1. An embodiment corresponding to claim 1 will be described with reference to FIGS. 1 to 4 showing the essential parts of an optical print head according to the present invention. In FIG. 1, members given the same reference numerals as those in FIG. 9 are the same members as those in FIG.

In this example, the long substrate 1 is the substrate holding jig 5
It is fixed by using a screw 9. On the substrate 1, a plurality of light emitting diode array elements 6-1, 6-2, ...
And drive elements 7-1, 7-3, ..., 7-2, 7-
4 ... are mounted and fixed. The light emitting diode array element and the driving element are bonded by a bonding wire 8 made of gold or aluminum.

As shown in FIGS. 2 and 3, an opening 11 is formed in a portion corresponding to the end of the substrate 1 which constitutes the envelope.

At least one shaft 10 is provided in the opening 11 so as to be parallel to the main scanning direction (longitudinal direction of the substrate 1) of the light emitting diode array element.
Is attached to. In this example, one substrate holding jig 5
It uses two shafts.

The substrate holding jig 5 is also formed with a screw hole 12 for fixing the substrate, and the substrate 1 and the substrate holding jig 5 are integrated by a screw 9 for fixing the substrate through the screw hole. Fixed.

As shown in FIGS. 2 and 3, the substrate holding jig 5 has a guide hole 13 formed therein. The shaft 10 is slidably inserted into the hole 13, and the substrate holding jig 5 is attached to the base 2 via the shaft. A lens array fixing jig 3 is also attached to the base 2, and the base 2 and the lens array fixing jig 3 constitute an envelope.

As described above, the substrate holding jig 5 is the base 2
Since the shaft 10 is attached to the shaft 10 so as to pass through the guide hole 13 and is integral with the substrate, the substrate holding jig is movable with the substrate only in the main scanning direction A with respect to the envelope. .

In this embodiment described above, the substrate holding jig 5, the shaft 10, the opening 11 and the like constitute a substrate fixing mechanism for moving the envelope in the main scanning direction.

The state of the optical printer head having the above-mentioned structure during the lighting drive will be described with reference to FIG.

FIG. 5A shows a state in which a long substrate 1 on which a light emitting diode array element and a driving element are mounted and fixed is fixed to a base 2 of an envelope at room temperature. In this state, the substrate 1 and the lens array 4 fixed to the envelope are optically adjusted.

When the substrate 1 and the envelope are fixed, the above-mentioned substrate fixing mechanism is constructed at two places near both ends of the substrate 1. The component of this substrate fixing mechanism is shown by reference numeral 14.

Further, at one place near the center of the substrate 1,
The substrate 1 and the base 2 of the envelope are directly fixed with screws 15. In this case, the material of the envelope of the optical print head is aluminum, and the substrate 1 has a length of about 3 in the main scanning direction A.
Alumina (Al ₂ O ₃ ) is used as the material.

On the substrate 1, a light emitting diode array element having a length of about 4 mm (64 dots per array element) having light emitting regions arranged at a rate of 400 dots per inch (400 dpi, about 16 dots / mm) is provided. 72 pieces are aligned and fixed in a line, and a driving integrated circuit (IC) for driving a light emitting diode array element is fixed and aligned in the vicinity thereof. As a result, the light emitting areas are aligned in a line over the entire length of the optical printer in the main scanning direction.

FIG. 5B shows a state in which the temperature of the optical print head is raised by driving the optical printer head adjusted and fixed at room temperature in this way. That is, when all the light emitting diodes are lit at a duty of 50%, the temperature of the substrate 1 rises to about 90 ° C and the temperature of the base 2 portion of the envelope rises to about 80 ° C.

Therefore, in the main scanning direction A, the portion of the base 2 of the envelope is L1 = about 0.7 mm, and the substrate 1 is L2.
= An elongation of about 0.2 mm occurs. In the fixed direction of the conventional long substrate, due to the difference in the extension in the main scanning direction, a force similar to that acting on a bimetal generally called is applied to this optical printer head, and the warp of the substrate 1 in the main scanning direction A is caused. This is what happened.

However, when the substrate fixing mechanism (indicated by reference numeral 14 in FIG. 5) including the substrate holding jig 5, the shaft 10, the opening 11 and the like according to FIGS. 1 to 3 is used, the expansion amount of the substrate 1 is increased. And the difference in the amount of expansion of the base part of the envelope,
The movement of the movable portion of the substrate holding mechanism in the main scanning direction A does not generate a force that causes the optical print head to warp, so that the substrate 1 does not warp.

As a result, the temperature rise due to the driving of the optical print head causes the substrate 1 to warp and the distance between the light emitting diode array element and the lens array to change, so that the projected image of the light emitting point on the photosensitive member is not blurred. A clear image can be output.

Further, the force for bending the substrate 1 generated by the difference in the amount of expansion due to the expansion of the substrate 1 and the envelope is generated by combining the envelope in which the substrate 1 is firmly fixed as in the conventional case. Since it is not necessary to have it, it is not necessary to increase the rigidity of the envelope so much. That is, the size and weight of the envelope can be reduced.

Example 2. An embodiment corresponding to claim 2 of the present invention will be described with reference to FIG. In this example, a stretchable coil spring 1 is attached to a shaft 10 planted in a base 2 of an envelope.
6 is attached so that the force between the base 2 of the envelope and the substrate holding jig 5 is constantly acting to separate them from each other in the main scanning direction A.

As a result, the substrate 1 attached to the substrate holding jig 5 is constantly subjected to a pulling force in the main scanning direction A toward both sides. Thereby, the flatness of the substrate 1 is improved.

As described above, in the long substrate 1 of the optical print head, the flatness of the substrate 1 is improved as compared with the prior art both when the optical position is adjusted at room temperature and when the temperature is increased by driving the optical print head. The blur of the projected image of the light emitting point on the photoconductor due to the variation of the relative optical position between the array element and the lens array is reduced, and a clear image can be output.

Example 3. An embodiment corresponding to claim 3 of the present invention will be described with reference to FIG. FIG. 7A is an overall explanatory view of the optical print head, and FIG. 7B is an enlarged view of the end portion of the base 2 portion of the substrate 1. Back surface of substrate 1 (surface opposite to the surface on which light emitting diode array elements are stacked and fixed)
And a heat conductive material 1 having fluidity between the base 2 of the envelope and
7. In this example, a high viscosity silicone grease for heat dissipation is applied.

In the conventional optical print head, as described in the section of the prior art, in order to maintain the optical distance once held at room temperature adjustment, the substrate 1 is firmly attached to the envelope with an adhesive or the like. It was stuck.

However, in the optical print head according to the present embodiment, the substrate 1 is different from the envelope in the amount of expansion of the substrate 1 and the envelope due to thermal expansion due to temperature rise when the optical print head is driven. Only have to move relatively.

Therefore, in this example, the fluid heat transfer material 17 is sandwiched between the substrate 1 and the base 2 of the envelope. Accordingly, the movement of heat from the substrate 1 to the envelope can be promoted without hindering the movement of the substrate with respect to the envelope, so that the heat dissipation of the substrate 1 is improved and the flatness of the substrate 1 is improved. After improvement, a clear image can be obtained in the end.

Example 4. Another example corresponding to claim 3 of the present invention will be described with reference to FIG. FIG. 8 is a perspective view of an essential part of an optical print head using the edge emitting light emitting diode array device according to the present invention. In the figure, reference numerals 3-1 and 3
Reference numeral -2 indicates a portion of the lens array fixing mechanism of the envelope. The members with other reference numerals are similar to the members with the reference numerals already described.

Also in this example, the substrate 1 is fixed to the base 2 of the envelope by using the substrate holding jig 5. In the edge-emitting optical print head according to this example, since the warp of the emission projection image on the photoconductor due to the warp of the substrate 1 due to the above-described temperature rise (see FIG. 15) does not occur, the driving condition of the optical print head It is possible to output a good image regardless of the above.

In this example, aluminum was used as the material for the envelope and the substrate holding mechanism, but good results can be obtained with other metal molded products. Also, although preferably metallic, other materials such as polycarbonate, polyphenylene sulfide (PPS), polybutylene terephthalate (PBT), or fiber reinforced plastics (FRP), metal matrix composite materials (MMC) thereof, etc. are also used. it can.

Silicon grease was used as the fluid heat transfer material in this example, but other materials, such as a rubber adhesive containing a metallic filler to improve heat transfer, and a silicon adhesive Organic gel materials such as gel materials can also give good results.

Further, by providing a mechanism for reducing friction such as a bearing between the guide hole of the holding component of the substrate holding mechanism and the shaft attached to the base, a better result can be obtained.

As described above, according to each of the embodiments of the present invention, the warp in the main scanning direction of the substrate on which the light emitting diode array element is mounted and fixed does not occur due to the temperature rise during the lighting drive of the optical print head.

Therefore, the relative positional variation between the light emitting diode array element and the lens array is reduced, and even if the temperature rises, the force for bending the substrate in the main scanning direction is not generated, so that the rigidity of the envelope can be improved. It is possible to provide an optical printhead that is smaller and lighter in size than the optical printhead of (1).

[0057]

As described above, according to the present invention, it is possible to provide a compact and lightweight optical print head capable of realizing high-density and high-quality printing.

[Brief description of drawings]

FIG. 1 is a perspective view of an essential part of an optical print head according to the present invention.

FIG. 2 is a sectional view of an essential part of an optical print head according to the present invention.

FIG. 3 is an explanatory diagram of a substrate holding mechanism of the optical print head according to the present invention.

FIG. 4 is a sectional view of a substrate holding mechanism of an optical print head according to the present invention.

FIG. 5 is an explanatory diagram of the operation of the optical print head according to the present invention.

FIG. 6 is an explanatory view of a substrate holding mechanism for another embodiment of the optical print head according to the present invention.

FIG. 7 is an explanatory diagram of another embodiment of the optical print head according to the present invention.

FIG. 8 is a perspective view of a main part of an edge emitting optical print head according to the present invention.

FIG. 9 is a perspective view of a conventional surface-type optical print head.

FIG. 10 is a diagram illustrating a state of a conventional optical print head during room temperature adjustment.

FIG. 11 is a diagram illustrating a state of the conventional optical print head after temperature rise during lighting drive.

FIG. 12 is a cross-sectional view of a conventional surface-type optical print head.

FIG. 13 is a perspective view of a conventional end-face type optical print head.

FIG. 14 is a diagram illustrating a state of a conventional end-face type optical print head during room temperature adjustment.

FIG. 15 is a diagram illustrating a state of a conventional end-face type optical print head after temperature rise during lighting drive.

[Explanation of symbols]

 1 substrate 2 envelope base 4 short focus lens array 6 light emitting diode array element 14 substrate fixing mechanism

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical indication H04N 1/036 A 9070-5C

Claims (3)

[Claims] 1. A long substrate on which a plurality of light emitting diode array elements are aligned and mounted on a surface and fixed, and a lens array arranged on an emission optical axis of the light emitting diode array elements.
It is provided with an enclosure for loading and enclosing the substrate and the lens array, and a substrate fixing mechanism for connecting the substrate and the envelope and for moving the enclosure in the main scanning direction. And optical printer head. 2. The optical printer head according to claim 1, wherein the substrate fixing mechanism includes a coil spring that constantly pulls the substrate toward both ends of the substrate in the main scanning direction. 3. An optical printer head according to claim 1, wherein a heat-conductive material having fluidity is sandwiched between a long substrate and an envelope.