JP2003039731A - Optical write head and method for working heat sink used in optical write head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To hold a high flatness without applying a stress to an adhesive layer interface between a substrate and a heat sink, efficiently conduct a heat energy of a light-emitting element to the heat sink, and prevent contamination of a chip mounting face due to bulging of an adhesive in an optical write head with the heat sink set to a base of the substrate where a light-emitting element array chip is mounted. SOLUTION: A plurality of protrusive ribs 7 are set to a substrate mounting face of the heat sink 3. The chip mounting substrate 5 is fixed by the adhesive 8 onto the ribs 7. One of the plurality of ribs 7 is set to the side of a rear face of a light-emitting array chip mounting position of the chip mounting substrate 5, and the outermost rib of the plurality of ribs 7 is set to form an adhesive reservoir for letting an excess part of the adhesive remain at the outside of the rib. A high-temperature conductive adhesive of a low-elasticity resin is used as the adhesive 8, which is applied to the inside of the ribs 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical writing head mounted on an electrophotographic printer and condensing light emitted from a light emitting element array by a lens array and projecting it onto a photosensitive member.

[0002]

2. Description of the Related Art An example of a conventional optical writing head mounted on an electrophotographic printer is shown in FIG. FIG. 1 is a sectional view of a conventional optical writing head.

A light emitting element array chip 36 is mounted on the ceramic substrate 33, and an aluminum substrate table 35 is mounted on the aluminum substrate table 35.
The driver substrate 34 and the ceramic substrate 33 are placed, and the ceramic substrate 33 and the driver substrate 34 are
C (Flexible Printed Circuit)
t: flexible substrate) 37 for electrical connection. An erecting equal-magnification lens array 31 is mounted on the lens support member 32, and a photosensitive drum (not shown) is provided on the optical axis of the erecting equal-magnification lens array 31. The erecting equal-magnification lens array 31 collects the light of the light emitting element array, irradiates the photosensitive drum, and forms a latent image on the surface of the photosensitive drum.

In this conventional optical writing head, an aluminum substrate base 35 on which a ceramic substrate 33 on which a light emitting element array chip 36 is mounted is mounted and a lens support member 32 on which an erecting equal-magnification lens array 31 is mounted are separately provided. And enables precise optical axis adjustment.

[0005]

However, in the conventional optical writing head, since the linear expansion coefficient of the ceramic substrate is different from that of the aluminum substrate stage, the ceramic substrate and the aluminum substrate are not used in the manufacturing process for mounting the ceramic substrate on the aluminum substrate stage. Stress distortion is generated between the substrate stands, causing warpage of the ceramic substrate,
There is a problem that the adhesive interface between the ceramic substrate and the aluminum substrate stand is peeled off.

Next, a manufacturing process for mounting the ceramic substrate on the aluminum substrate base will be described. 1. The ceramic substrate and the aluminum substrate base are fixed with an adhesive. 2. The FPC is adhesively fixed to the ceramic substrate. 3. The light emitting element array chip is mounted on the ceramic substrate. 4. Curing is performed at about 150 ° C. in order to cure the adhesive that fixes the light emitting element array chip to the ceramic substrate. 5. Wire bonding is performed for electrical connection between the light emitting element array chip and the FPC.

In the above process, the aluminum linear expansion coefficient is set to 22 × 10 ⁻⁶ / ° C. in the curing step after bonding the ceramic substrate and the aluminum substrate stand.
The ceramic linear expansion coefficient is 7 × 10 ⁻⁶ / ° C., the curing temperature is 150 ° C., the room temperature is 25 ° C., and the temperature difference Δt is 125.
° C. and (150 ℃ -25 ℃ = 125 ℃ ), when the length of the substrate and 360 mm (A3 size), the distortion length between ^{both, 0.675 (15 × 10 -6 ×} 125 × 360 = 0.
675) mm, excessive stress is applied to the interface of the adhesive layer to cause peeling of the adhesive surface, and due to the bimetal phenomenon due to the difference in strain between the ceramic substrate and the aluminum substrate base, the light emitting element array chip mounting on the ceramic substrate is performed. It deteriorates the flatness of the surface.

[0008] For such a problem, for example, an adhesive layer having a large thickness and an adhesive having a low hardness after curing is used to absorb the distortion between the two by elastic deformation of the adhesive. However, if the thickness of the adhesive layer is increased, there is a problem in that the flatness of the light emitting element array chip mounting surface of the ceramic substrate cannot be obtained.

Ultrasonic waves generated during wire bonding with a gold wire between the light emitting element array chip and the FPC are absorbed by the adhesive layer, causing defective welding of the gold wire.

Furthermore, if the amount of adhesive applied between the ceramic substrate and the aluminum substrate base is small, a void layer is formed between the two, and the adhesive strength is lowered and the void layer intervenes to cause a light emitting element It hinders the function of transferring heat energy to the substrate table. If there is a large amount, the adhesive of the ceramic substrate and the substrate stand will stick out, and the F
It will contaminate the PC attachment surface and the chip mounting surface.

Further, since the focal length of the optical lens used in the high resolution optical writing head is extremely short, the distance between the light emitting element array chip and the erecting equal-magnification lens array must be strictly controlled. If the optical components are placed out of the prescribed focal length, the latent image shape on the photosensitive drum becomes unstable, or a virtual image occurs,
There is a problem that the quality of the printed image is degraded.

In order to obtain high quality printing quality, it is necessary to improve the accuracy of arrangement of each optical component, but this requires a high precision material for holding the optical components.
This naturally causes an increase in component cost. For example, a glass epoxy substrate or the like is generally used as a chip mounting substrate on which the light emitting element array chip is mounted. However, since the glass epoxy substrate has a low self-shape-retaining property, a chip between each light emitting element is used. It is difficult to control the height with high precision.

Actually, the surface accuracy is guaranteed with reference to the joint surface between the chip mounting board and the heat sink (board base) on which the chip mounting board is mounted, or the erecting equal-magnification lens and the chip mounting board are supported by the lens holder. In the optical writing head, it is general to guarantee the surface accuracy with reference to the joint surface between the chip mounting substrate and the lens holder. However, it is known that the lens holder is generally a resin molded product and the heat sink is made of an aluminum extruded material. However, both of them must have a high surface accuracy on the joint surface with the chip mounting board. It is difficult.

A means for polishing the bonding surface of the heat sink to the chip mounting substrate is conceivable, but in the polishing processing or the cutting processing, it is general to process the heat sink after fixing it with a magnet or a vise. Due to heat generation and cutting stress on the cutting surface during processing, the stress balance between the cutting surface side and the anti-cutting surface side is disrupted, and when the heat sink is removed from a fixing jig such as a magnet, the heat sink warps. By processing the front and back of the heat sink several times to equalize the stress balance between the front and back, a surface with high flatness can be obtained. However, a heat sink that requires such a process becomes very expensive.

The present invention has been made in view of such conventional problems, and its purpose is to use a mode in which a substrate on which a light emitting element array chip is mounted and a heat sink (substrate base) are fixed by adhesion. Even if the adhesive layer interface is not stressed, high flatness can be maintained, and the heat energy of the light emitting element can be efficiently propagated to the heat sink (substrate table), so that the mounting surface can be prevented from being contaminated by the adhesive protruding. It is to provide an optical writing head.

[0016]

According to the present invention, a lens array is provided on the optical axis of light emitted by a light emitting element of a light emitting element array chip, and a heat sink is provided on a base of a substrate on which the light emitting element array chip is mounted. In the optical writing head, the heat sink is provided with a plurality of convex ribs on the attachment surface of the substrate in the longitudinal direction of the heat sink, and the substrate is fixed on the ribs of the heat sink by fixing means. It is characterized by being

It is preferable that one of the plurality of ribs is provided on the back surface side of the light emitting element array chip mounting position of the substrate, and the rib is provided across both ends in the longitudinal direction of the heat sink. Preferably.

Further, the fixing means is preferably an adhesive, and the outermost rib of the plurality of ribs in the direction orthogonal to the longitudinal direction of the heat sink is the adhesive on the outer side of the rib. Is preferably provided so as to form an adhesive reservoir for accumulating the surplus portion.

Further, it is preferable that the adhesive is a high thermal conductive adhesive made of a low elastic resin, and the adhesive is preferably applied between the ribs.

Further, it is preferable that the heat sink and the substrate are provided with positioning means so that one of the plurality of ribs is provided on the rear surface side of the light emitting element array chip mounting position of the substrate.

Further, it is preferable that the heat sink has an opening on its side surface or a hollow portion inside, and the heat sink has a U-shaped cross section in the longitudinal direction of the heat sink. It is preferable that the opening is provided, or the hollow portion having a rectangular or circular cross section is provided over the longitudinal direction of the heat sink.

The lens array is preferably a rod lens array or a resin erecting equal-magnification lens array.

The light emitting element array chip is preferably a self-scanning light emitting element array chip.

Further, according to the present invention, in a method of processing a heat sink used for an optical writing head, the heat sink is set so that a surface having the rib is in contact with a processing surface of a single-sided lapping device, and a tip portion of the rib is set. Is characterized by being lapped.

Further, it is preferable that the tip portion of the rib is lapped so as to come into contact with the processing surface of the single-sided lapping device by substantially the weight of the heat sink.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 2 is a cross-sectional view of the embodiment of the optical writing head of the present invention in a direction orthogonal to the head longitudinal direction.

The heat sink 3 is provided with convex ribs 7 on the chip mounting board mounting surface, the chip mounting board 5 is fixed onto the ribs 7 with an adhesive 8, and the light emitting element is mounted on the chip mounting board 5. The light emitting element array chips 6 arranged in rows are mounted.

An erecting equal-magnification lens array 2 in which erecting equal-magnification lenses are arranged in a row is attached to the support 1 by means of adhesion or the like, and a heat sink 3 emits light emitted from the light emitting element. Is adjusted and fixed so that the optical axis of the optical axis and the optical axis center of the erecting equal-magnification lens coincide with each other, and the driver substrate 4 is fixed by bolts 9.

Electronic elements such as ICs for driving the light emitting elements are mounted on the driver substrate 4. The driver substrate 4 and the chip mounting substrate 5 are FPC (Flexi).
ble Printed Circuit (flexible substrate) 10 for electrical connection. The heat sink 3 and the chip mounting board 5 are covered with a resin cover 11.

FIG. 3 is a perspective view for explaining the positional relationship between the chip mounting board on which the light emitting element array chip is mounted and the heat sink.

On the chip mounting board mounting surface of the heat sink, a plurality of convex ribs are provided over both ends in the longitudinal direction of the heat sink, and one of the plurality of ribs is
It is provided immediately below the light emitting element array chip 6. In this embodiment, the case where three ribs are provided on the chip mounting board mounting surface will be described.

When three ribs are provided, the ribs are
The heat sink 3 is provided on the chip mounting board mounting surface near the center and both ends in the direction orthogonal to the longitudinal direction of the heat sink 3. Ribs 7 provided near the center
Is provided on the back surface side of the chip mounting substrate 5 where the light emitting element array chip 6 is mounted, that is, directly below the light emitting element array chip 6.

The ribs 7 provided near both ends are the ribs 7.
As shown in FIG. 4, it is provided at a position 0.5 to 3.0 mm from the edge portion of the heat sink 3 so as to form an adhesive reservoir for accumulating an excessive portion of the adhesive on the outer side of the heat sink 3. The height of the rib 7 is preferably 0.1 to 1.0 mm.

The ribs 7 are convex protrusions provided in the longitudinal direction of the heat sink 3, and it is preferable that the ribs 7 are provided over both ends in the longitudinal direction, but it is not necessary to be provided over both ends, and it is not necessary. It may be provided continuously.

Since the ribs other than the ribs provided on the rear surface side of the light emitting element array chip mounting position serve as supporting portions when fixing the chip mounting substrate 5 to the heat sink 3, they need to be provided continuously. Alternatively, the heat sink 3 may have a short length, and one or more heat sinks 3 may be provided.

If a wide rib is provided on the rear surface side of the light emitting element array chip mounting position and the chip mounting substrate 5 can be supported only by this rib, only one rib is provided on the heat sink 3. There are cases.

Further, as shown in FIG. 3, the heat sink 3 is provided for positioning the chip mounting board 5 at both end portions of the heat sink 3 in the longitudinal direction (chip scanning direction).
A book reference pin 12 is provided. On the chip mounting substrate 5, reference holes 13 for fitting with the reference pins 12 are provided at portions corresponding to the positions of the two reference pins of the heat sink 3. By fitting the reference pin 12 into the reference hole 13, the rib 7 provided near the center of the heat sink 3 is positioned on the rear surface side of the light emitting element array chip mounting position of the chip mounting substrate 5.

Here, as the chip mounting substrate 5, a ceramic substrate, a glass epoxy substrate or an iron substrate is used.

Further, the surface of the tip portion of the rib 7 which comes into contact with the chip mounting substrate 5 is subjected to precision processing so as to have flatness.

Next, a method of manufacturing a heat sink in which the tips of the ribs have a high flatness will be described.

For the heat sink, a metal-based or non-ferrous metal-based material having good thermal conductivity is used. When using an aluminum material, an extruded material is used. In the case of a metallic material, it is preferable to make it by a cold drawing method. The heat sink made by such a manufacturing method is 0.1 mm /
It is possible to have a flatness of about 300 mm. However, since the focal length of the resin lens for high-resolution use is very short and the accuracy of about 60 μm is required, the accuracy of the rib mounted on the heat sink on the mounting surface of the light emitting element mounting substrate requires higher accuracy. To be done. Therefore, the light emitting element mounting board mounting surface at the tip of the rib is a lapping machine (lapping device) with the following specifications.
To obtain a high precision surface.

FIG. 5 is a plan view of the lapping plate portion of the lapping machine. A single-sided lapping machine is used as the lapping machine, and a plurality of works (heat sinks) 20 can be inserted into the carrier 21. This single-sided lapping machine can process in a relatively short time,
Since a large number of heat sinks can be simultaneously processed in one batch of the lapping machine, it is suitable for mass production.

The lapping plate 19, the internal gear 22, and the sine gear 23 each have a separate drive system so that the rotational speed can be varied, or the peripheral speeds of the gears and the variable transmission are the same from the same drive source. It can be changed.

The carrier 21 in which the work 20 is inserted has two types of rotation, that is, the center portion of the carrier 21 as a starting point and the lapping plate 19 as a starting point due to the difference in the number of rotations of the internal gear 22 and the sun gear 23. Is given.

Since the carrier 21 rotates from the center of the carrier as a starting point, the work 20 is cut and polished while moving between the center of the lapping plate 19 and the outer periphery thereof. The peripheral speed difference is averaged, and the polishing rate of each work 20 is made constant.

The floating abrasive grains are preferably used in the range of # 600 to 1200. The load between the work 20 and the lapping plate 19 is preferably about 50 to 300 g / cm ² when iron is used for the heat sink and about 30 to 250 g / cm ² when aluminum is used for the heat sink. . Therefore, if necessary, weights are placed on the upper part of the heat sink so that the above settings are made. In that case, it is necessary to install the heat sink so that the load is evenly distributed over the length direction. When the work 20 is inserted into the carrier 21, the work 20 is arranged so that the joint surface with the light emitting element mounting substrate is in contact with the lapping plate 19.

FIG. 6 is a partial sectional view of the lapping plate portion of the lapping machine. The work (heat sink) 20 is set with the surface having the ribs facing down.
By using the lapping machine, the surface of the work (heat sink) 20 in contact with the lapping plate 19 is
Polished by the floating abrasive grains 24 penetrating between the two, high flatness is obtained. At that time, even if a material stress difference between the polishing surface and the anti-polishing surface occurs and a slight warp occurs, the amount of the warp is further polished. Does not receive chucking external force. For this reason,
The accuracy during processing is maintained as it is even after being taken out from the processing machine, so that high processing accuracy can be obtained.

As described above, during the lapping process, the heat sink is in contact with the lapping plate, which is the machined surface of the single-sided lapping machine, by almost only its own weight. Therefore, the work is not deformed after the lapping process, and the flatness is highly accurate. Can be easily obtained. Therefore, a heat sink having high flatness can be manufactured at a relatively low cost.

As shown in FIG. 7, the rod lens mounting surface of the support may be simultaneously polished with high accuracy by lapping.

Next, a method of fixing the chip mounting board to the heat sink will be described.

First, as shown in FIG. 8, an adhesive 8 is applied between the ribs, that is, inside the rib 7. Since the adhesive 8 is applied to the inside of the rib 7, the rib 7 can be prevented from flowing out to the outside of the rib 7 as a weir.

As the adhesive agent 8, an adhesive agent of low elasticity resin (JIS-A hardness of 100 or less) is used. By using the low-elasticity resin adhesive, the strain caused by the difference in thermal expansion coefficient between the heat sink and the chip mounting substrate is absorbed in the low-elasticity resin layer, so that the interface peeling of the adhesive layer and the deformation of the member can be prevented. .

As the adhesive 8, it is desirable to use a thermosetting type high thermal conductive adhesive (heat conductivity of 1.0 W / m · k or more).

Next, after fitting the reference pins of the heat sink 3 into the reference holes of the chip mounting board 5, the jig 1 shown in FIG.
5, the silicon sheet 17 is sandwiched between the chip mounting substrate 5 and the chip mounting substrate 5, and the chip mounting substrate 5 is mounted on the air cylinder 16
Hold it down with an even load. Hold it down,
By raising the temperature of the surface plate 18 provided below the heat sink 3, the adhesive 8 is hardened, and the chip mounting substrate 5 is adhesively fixed to the heat sink 3.

After the adhesive 8 is hardened, the volume of the chip mounting substrate 5 is slightly reduced between the ribs as shown in FIG. Since the flatness in the vicinity of the mounting surface of the light emitting element array chip 6 follows the accuracy of the rib tip at the center of the heat sink 3, it is possible to obtain high surface accuracy without depending on the accuracy of the thickness of the adhesive 8. .

Further, since the outer ribs are provided outside the ribs so as to form an adhesive reservoir for retaining the surplus adhesive, even if the amount of the applied adhesive is too large. As shown in FIG. 10, it is possible to prevent the adhesive from remaining on the substrate surface of the chip mounting substrate 5 due to the adhesive remaining in the adhesive reservoir outside the ribs. FIG. 11 is a front view of the heat sink in a state where the chip mounting board is adhered, and shows a state in which the adhesive remains in the adhesive reservoir outside the ribs.

In the structure of the above-described embodiment, since the rib of the heat sink is located immediately below the mounting surface of the light emitting element array chip, the flatness of the chip mounting board in the vicinity of the chip mounting portion depends on the adhesive thickness. It is possible to maintain high flatness without being affected by. Further, since the rib of the heat sink is located immediately below the mounting position of the light emitting element array chip, the heat energy of the light emitting element is propagated to the entire heat sink via this rib.

Further, in the above-mentioned embodiment, since the high heat conductive adhesive is used for bonding the heat sink and the chip mounting substrate, the heat conduction at the bonded portion is also good, and the heat energy of the light emitting element can be easily generated. It is possible to obtain an optical writing head that can be transmitted to a heat sink, can reduce the temperature rise of the light emitting element, and can output a high-quality image with little density unevenness.

Further, in the above-described embodiment, since the rib is formed so as to form the adhesive reservoir for accumulating the surplus portion of the adhesive on the outside of the rib, the protrusion of the adhesive can be prevented and the adhesive can be prevented. It is possible to prevent the chip mounting surface from being contaminated by the protrusion.

Further, in the above-mentioned embodiment, the adhesive is a low elastic resin, and the thickness of the adhesive can be made relatively thick. Therefore, elastic deformation inside the adhesive layer causes thermal strain between the two parts. Be absorbed. Therefore, the load applied to the adhesive interface and the member is reduced, and the deformation of the component and the peeling of the adhesive interface are also reduced.

In the above-described embodiments, the case where the chip mounting board is fixed to the heat sink using an adhesive has been described. However, the present invention is not limited to this, and the chip mounting board may be bolted to the heat sink. You may fix using a fixing means.

Further, in the above-described embodiments, the heat sink may be provided with an opening portion on the side surface or a hollow portion inside in order to increase the heat radiation surface and enhance the heat radiation effect.

12, 13 and 14 are views showing an example of the shape of the heat sink. In FIG. 12, an opening having a U-shaped cross section is provided on the side surface of the heat sink across both ends in the longitudinal direction of the heat sink. In FIG. 13, a hollow portion having a rectangular cross section is provided across both ends of the heat sink in the longitudinal direction. In FIG. 14, a hollow portion having a circular cross section is provided across both ends in the longitudinal direction of the heat sink. It is preferable to provide the opening and the hollow portion over both ends in the longitudinal direction of the heat sink, but it is not always necessary to provide over both ends in the longitudinal direction, and as long as the heat radiation effect can be improved, what length Any shape may be used, or the shape may be discontinuous.

Further, in the above-described embodiment, a self-scanning light emitting element array chip can be used as the light emitting element array chip. Note that the self-scanning light-emitting element array is a light-emitting element array that has a self-scanning circuit and has a function of sequentially transferring light-emitting points.

Regarding the self-scanning type light emitting element array, JP-A-1-238962, JP-A-2-14584, JP-A-2-92650, and JP-A-2-926 are available.
No. 51, etc., it is easy to mount as a light source for a printer head, and the interval between light emitting elements can be made small,
It has been shown that a compact printer head can be manufactured. Further, in Japanese Patent Laid-Open No. 2-263668,
A self-scanning light emitting element array having a structure in which the transfer element array is used as a shift portion and is separated from the light emitting element array which is the light emitting portion is proposed.

FIG. 15 shows an equivalent circuit diagram of a self-scanning light emitting element array having a structure in which a shift portion and a light emitting portion are separated.
The shift section has transfer elements T ₁ , T ₂ , T ₃ , ... And the light emitting section has write light emitting elements L ₁ , L ₂ , L ₃ ,. These transfer element and light emitting element are composed of a three-terminal light emitting thyristor. The configuration of the shift section uses diodes D ₁ , D ₂ , D ₃ , ... To electrically connect the gates of the transfer elements to each other. V _GK is a power source (usually 5 V) and is connected to the gate electrodes G ₁ , G ₂ , G ₃ , ... Of each transfer element via the load resistance R _L. Further, the gate electrodes G ₁ , G ₂ , G ₃ , ... Of the transfer element are also connected to the gate electrode of the writing light emitting element. A start pulse φ _S is applied to the gate electrode of the transfer element T ₁ , and the transfer clock pulse φ is alternately applied to the anode electrode of the transfer element.
1, φ2 are applied, and the write signal φ _I is applied to the anode electrode of the writing light emitting element.

In the figure, R1, R2, R _S and R _I are
Each shows a current limiting resistance.

The operation will be briefly described. First, the transfer clock
If the voltage of pulse pulse φ1 is H level, transfer element T₂Is o
It is assumed that it is in the online state. At this time, the gate electrode G₂Potential of
Is V _GKFrom 5 V to almost zero V. This potential drop
The lower effect is diode D₂By the gate electrode G₃In
And the potential is set to about 1 V (diode D₂Forward direction
Rising voltage (equal to diffusion potential)). Only
And diode D₁Is a reverse bias condition, so the gate
Electrode G₁No potential is connected to the gate electrode G₁of
The potential remains 5V. On-voltage of light emitting thyristor
Is the gate electrode potential + pn junction diffusion potential (about 1 V)
Since it is approximated, the H level of the next transfer clock pulse φ2
Bell voltage is about 2V (transfer element T₃In order to turn on
Above the required voltage) and about 4V (transfer element T_FiveTurn on
(Voltage required to operate)
Child T₃Only turn on, other transfer elements remain off
Can be Therefore, two transfer clock pulses
The ON state is transferred at the switch.

The start pulse φ _S is a pulse for starting such a transfer operation.
At the same time when _{S is set} to H level (about 0 V), the transfer clock pulse φ2 is set to H level (about 2 to about 4 V), and the transfer element T ₁ is turned on. Immediately after that, the start pulse φ _S is returned to the H level.

Now, assuming that the transfer element T ₂ is in the ON state, the potential of the gate electrode G ₂ becomes almost 0V. Therefore, if the voltage of the write signal φ _I is equal to or higher than the diffusion potential (about 1 V) of the pn junction, the light emitting element L ₂ can be brought into a light emitting state.

On the other hand, the gate electrode G ₁ is about 5V and the gate electrode G ₃ is about 1V. Therefore, the writing voltage of the light emitting element L ₁ is about 6V, and the writing voltage of the light emitting element L ₃ is about 2V. From this, the voltage of the write signal φ _I for writing only to the light emitting element L ₂ is in the range of 1 to 2V. When the light emitting element L ₂ is turned on, that is, enters the light emitting state,
The emission intensity is determined by the amount of current flowing in the write signal φ _I , and image writing can be performed at any intensity. In order to transfer the light emitting state to the next light emitting element, the voltage of the write signal φ _I line must be once set to 0 V and the light emitting element which is emitting light must be turned off once.

In the above-described embodiment, the erecting equal-magnification lens array may be a rod lens array or a resin erecting equal-magnification lens array. FIG.
[FIG. 3] is a cutaway perspective view showing an example of the configuration of a rod lens array. The rod lens array is an array of rod lenses 25 in which the refractive index decreases from the central axis toward the periphery in one or two rows, and can form an erecting equal-magnification image. FIG. 17 is a perspective view showing an example of the configuration of a resin erecting equal-magnification lens array. The resin erecting equal-magnification lens array is formed by stacking two or more lens array plates 26 each including the monocular lenses 27 arranged in one or two rows, and can form an erecting equal-magnification image. The monocular lens 27 has the same focal length and aperture, and one surface is convex or both surfaces are convex.

[0074]

As described above, according to the present invention, since the rib of the heat sink is provided directly below the mounting surface of the light emitting element array chip, the flatness of the chip mounting substrate near the chip mounting portion is High flatness can be maintained without being affected by the thickness.

Further, according to the present invention, since the rib is formed outside the rib so as to form an adhesive reservoir for accumulating an excessive portion of the adhesive, it is possible to prevent the adhesive from protruding.

Further, in the present invention, since the low elastic resin adhesive is used as the adhesive, the strain caused by the difference in the coefficient of thermal expansion between the heat sink and the chip mounting substrate is absorbed in the low elastic resin layer and bonded. Interfacial peeling of layers and deformation of members can be prevented.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a conventional optical writing head.

FIG. 2 is a cross-sectional view showing an embodiment of an optical writing head of the present invention.

FIG. 3 is a perspective view illustrating a positional relationship between a chip mounting substrate on which a light emitting element array chip is mounted and a heat sink.

FIG. 4 is a cross-sectional view of a chip mounting substrate and a heat sink for explaining rib positions.

FIG. 5 is a plan view of a lapping plate portion of the lapping machine.

FIG. 6 is a partial cross-sectional view of a lapping plate portion of the lapping machine.

FIG. 7 is a diagram showing another example of a member to be polished.

FIG. 8 is a cross-sectional view of a heat sink for explaining a coated state of an adhesive.

FIG. 9 is a cross-sectional view for explaining a method of fixing the chip mounting board to the heat sink with a jig.

FIG. 10 is a cross-sectional view of a heat sink with a chip mounting board adhered thereto.

FIG. 11 is a front view of the heat sink with the chip mounting substrate adhered thereto.

FIG. 12 is a diagram showing another example of the shape of the heat sink.

FIG. 13 is a diagram showing another example of the shape of the heat sink.

FIG. 14 is a diagram showing another example of the shape of the heat sink.

FIG. 15 is a diagram showing an equivalent circuit of a self-scanning light emitting element array.

FIG. 16 is a cutaway perspective view showing an example of the configuration of a rod lens array.

FIG. 17 is a perspective view showing an example of the configuration of a resin erecting equal-magnification lens array.

[Explanation of symbols]

1 support 2,31 Erecting equal-magnification lens array 3 heat sink 4,34 Driver board 5 chip mounting board 6,36 Light emitting element array chip 7 ribs 8 adhesive 9 bolts 10,37 FPC 11 resin cover 12 reference pins 13 Reference hole 15 jigs 16 air cylinders 17 Silicone coat 18 surface plate 19 wrapping plate 20 work 21 career 22 Internal Gear 23 Sun Gear 24 floating abrasive 25 rod lens 26 Lens array plate 27 monocular lens 32 lens support member 33 Ceramic substrate 35 Aluminum substrate stand

Claims (14)

[Claims] 1. An optical writing head comprising a lens array on the optical axis of light emitted by a light emitting element of a light emitting element array chip, and a heat sink on the base of a substrate on which the light emitting element array chip is mounted. Is characterized in that a plurality of convex ribs are provided in a longitudinal direction of a heat sink on a mounting surface of the substrate, and the substrate is fixed by fixing means on the rib of the heat sink. head. 2. The optical writing head according to claim 1, wherein one of the plurality of ribs is provided on the rear surface side of the light emitting element array chip mounting position of the substrate. 3. The optical writing head according to claim 1, wherein the ribs are provided over both ends in the longitudinal direction of the heat sink. 4. The optical writing head according to claim 1, wherein the fixing means is an adhesive. 5. The outermost rib of the plurality of ribs in a direction orthogonal to the longitudinal direction of the heat sink is provided so as to form an adhesive agent reservoir for retaining an excessive portion of the adhesive agent on the outer side of the rib. The optical writing head according to claim 4, wherein the optical writing head is provided. 6. The optical writing head according to claim 4, wherein the adhesive is a high thermal conductive adhesive made of a low elastic resin. 7. The optical writing head according to claim 4, wherein the adhesive is applied between the ribs. 8. The heat sink and the substrate are provided with positioning means so that one of the plurality of ribs is provided on the rear surface side of the light emitting element array chip mounting position of the substrate. The optical writing head according to any one of 2 to 7. 9. The optical writing head according to claim 1, wherein the heat sink is provided with an opening on a side surface thereof or has a hollow portion inside thereof. 10. The heat sink is provided with an opening having a U-shaped cross section in the longitudinal direction of the heat sink, or a hollow portion having a rectangular or circular cross section in the longitudinal direction of the heat sink. 9. The optical writing head according to claim 1, wherein the optical writing head is provided. 11. The optical writing head according to claim 1, wherein the lens array is a rod lens array or a resin erecting equal-magnification lens array. 12. The optical writing head according to claim 1, wherein the light emitting element array chip is a self-scanning light emitting element array chip. 13. A method of processing a heat sink used for an optical writing head according to claim 1, wherein the heat sink is set such that a surface having the rib is in contact with a processed surface of a single-sided lapping device. And lapping the tip portions of the ribs. 14. The method of processing a heat sink according to claim 13, wherein the tip portion of the rib is lapped so as to come into contact with the processing surface of the single-sided lapping device by substantially the weight of the heat sink.