JP2003054028A - Optical writing head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical writing head having a head structure employing a metal substrate in which the head width can be made relatively narrow, heat dissipation of a light emitting element is improved remarkably and a high quality print image can be obtained. SOLUTION: A light emitting element array 4 is mounted on an iron substrate 5 where a fine wiring pattern is formed by photoresist etching method and the iron substrate 5 is bonded through an adhesive to a heat sink 3 for dissipating heat generated from the light emitting element array 4. The light emitting element array 4 is mounted on the side of the iron substrate 5 where burrs are generated at the time of producing the substrate. The heat sink 3 is made of a material having the linear expansion coefficient of iron or an equivalent linear expansion coefficient.

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 FIG. 1 shows an example of a conventional optical writing head used in an electrophotographic printer or the like. FIG. 1 is a sectional view of a conventional optical writing head in a direction orthogonal to the head longitudinal direction. In the conventional optical writing head, the light emitting element chips 54 in which the light emitting elements are arranged in rows on the substrate 53 are
An erecting equal-magnification lens array 51, in which erecting equal-magnification lenses are arranged in a row in the longitudinal direction of the head, is mounted by a resin cover 52 on the optical axis of light emitted from the light-emitting element. There is. A photosensitive drum 55 is provided on the optical axis of the erecting equal-magnification lens array 51.

The erecting equal-magnification lens array 51 collects the light of the light emitting element and irradiates it on the photosensitive drum 55. The photosensitive drum 55 is charged by means such as corona discharge, and the light-irradiated portion of the surface of the photosensitive drum 55 changes in potential characteristics and a latent image is formed.

In the conventional optical writing head, it is known that the light amount of the light emitting element decreases by about 0.5% when the temperature rises by 1 ° C. Therefore, the self-heating energy of the light emitting element is transferred to other members. It is required to propagate efficiently. Further, when mounting the light emitting element chip on the substrate, a thermosetting adhesive having high thermal conductivity is used. To cure the adhesive, a thermal history of about 150 ° C. for 1 hour is used. Need before and after.

[0005]

However, in the above-mentioned conventional optical writing head, the glass epoxy substrate is adopted as the material of the substrate on which the light emitting element chip is mounted, and the glass epoxy substrate and the glass are thermosetting. Since it is a composite material of resin, the coefficient of thermal conductivity is low, which causes an increase in temperature of the light emitting element chip and a decrease in printing density.

Further, since the glass epoxy substrate has a large difference in linear expansion coefficient from the light emitting element chip, it is
Internal stress is generated in the light emitting element chip, which causes defective light emission, and deterioration in reliability due to a decrease in interface strength of the adhesive layer and displacement of the mounting position of the light emitting element chip.

In order to solve such a problem, in JP-A-61-280685, the material of the substrate on which the light emitting element chip is mounted is made of a material having excellent thermal conductivity and a linear expansion coefficient close to that of the light emitting element chip. It is proposed to mount the light emitting element chip on the metal substrate by using the metal material, but since the wiring pattern is not provided on the metal substrate itself,
It is necessary to install an insulating substrate having a wiring pattern in the vicinity of the metal substrate, which is a factor that increases the cost due to an increase in the number of parts and cannot reduce the head width.

Further, Japanese Patent Laid-Open No. 1-280571 proposes a structure in which a light emitting element chip and a driving IC are mounted on a metal substrate, but since there is no means for forming a fine pattern on the metal substrate, It is necessary to increase the width of the metal substrate, which hinders the narrowing of the head. Also, by adopting a metal substrate, the heat conduction between the light emitting element chip and the metal substrate is dramatically improved, but the heat dissipation area of the metal substrate itself is relatively small, so the temperature of the metal substrate itself rises. As a result, there is a problem that the temperature of the light emitting element chip is increased and the print density is decreased.

As described above, in the conventional optical writing head using a metal substrate, a specific manufacturing method for forming a fine pattern on the metal substrate has not been established, and in the high resolution head, a large number of Since the pattern is required, there is a problem that the substrate width is increased and the head width is expanded.

Further, since the metal substrate is a flat plate and the heat radiation area is small due to the small heat radiation area, the temperature of the metal substrate itself rises due to the shortage of the heat radiation area of the metal substrate itself, and the temperature rise of the light emitting element chip. There was a problem of inviting.

Further, the metal substrate is generally composed of a plate material having a thickness of 0.5 to 3 mm in consideration of the manufacturing cost, and the metal material having this thickness maintains linearity in the longitudinal direction. However, it is difficult to hold the light-emitting element chip mounted on the metal substrate with good planarity. No. 3 of JP-A-1-280571
In the structure tying with the resin frame in the figure, a structure for maintaining the linearity of the metal substrate in the longitudinal direction has been proposed, but with a resin molded product, it is difficult to maintain high surface accuracy, Further, since it is difficult to maintain the mechanical strength, shape retention is also difficult.

The present invention has been made in view of such conventional problems, and an object thereof is to compare head widths even when light emitting element chips are mounted at high density in a head structure using a metal substrate. (EN) It is possible to provide an optical writing head which can be made narrower and which dramatically improves heat dissipation of a light emitting element chip and can obtain a high-quality printed image.

[0013]

SUMMARY OF THE INVENTION According to the present invention, light emitted from a light emitting element array in which light emitting elements are arranged in a row is condensed by a lens array in which lenses are arranged in a row and projected onto a photoreceptor. In the write head, the light emitting element array is mounted on a metal substrate on which a wiring pattern is formed, and the metal substrate is fixed to a heat sink for radiating heat from the light emitting element array.

It is preferable that the metal substrate has a surface on which a burr generated at the time of manufacturing the substrate is mounted as a surface on which the light emitting element array is mounted, and the heat sink is made of the same material as the metal substrate or the same linear expansion coefficient. Preferably, the heat sink is provided with alignment pins at least at both end portions in the longitudinal direction of the heat sink, and the metal substrate is for inserting alignment pins at positions corresponding to the alignment pins. It is preferable that the metal substrate is provided with a hole, and the metal substrate is aligned and fixed to the heat sink by inserting and fitting the alignment pin into the alignment pin insertion hole.

Further, the present invention provides an optical writing head for condensing light emitted from a light emitting element array having light emitting elements arranged in a row by a lens array having lenses arranged in a row and projecting the light onto a photosensitive member. The light emitting device array is mounted on a metal substrate on which a wiring pattern is formed, and the metal substrate is engaged with and fixed to a leg portion of a housing supporting the lens array.

[0016] It is preferable that the metal substrate has a surface on which a burr generated at the time of manufacturing the substrate does not project as a surface on which the light emitting element array is mounted, and the housing is made of the same material as the metal substrate or the same linear expansion coefficient. The housing is preferably made of a material having a coefficient, the housing is provided with alignment pins at least at both ends in the longitudinal direction of the housing, and the metal substrate is for inserting alignment pins at positions corresponding to the alignment pins. It is preferable that the metal substrate is provided with a hole, and the metal substrate is aligned and fixed to the housing by inserting and aligning the alignment pin into the alignment pin insertion hole.

Further, it is preferable that the metal substrate is made of a coil-shaped material so that the longitudinal direction of the metal substrate corresponds to the lengthwise direction of the coil-shaped material. It is preferably an iron substrate, an aluminum substrate, a stainless steel substrate, a nickel alloy substrate, a copper alloy substrate or an Invar alloy substrate.

The wiring pattern is preferably formed by a photoresist etching method.

The lens array is preferably a rod lens array or a resin erecting equal-magnification lens array, and the light emitting element array is preferably a self-scanning light emitting element array.

[0020]

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

FIG. 2 shows the first part of the optical writing head of the present invention.
FIG. 3 is a cross-sectional view of the embodiment of the present invention in a direction orthogonal to the head longitudinal direction. 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 such as adhesion, and an iron substrate 5 as a metal substrate is adhesively fixed to the heat sink 3. The light emitting element array 4 in which the light emitting elements are arranged in a row is mounted on the iron substrate 5.

The heat sink 3 is adjusted so that the optical axis of the light emitted from the light emitting element coincides with the optical axis center of the erecting equal-magnification lens, and is fixed to the support 1 by the bolt 6.

A driver substrate (not shown) on which an electronic element such as an IC for driving the light emitting element array 4 is mounted is fixed to the support 1 by bolts, and the driver substrate and the light emitting element array 4 are separated from each other. , And are electrically connected by a cable (not shown).

FIG. 3 is a perspective view showing a state where the iron substrate is attached to the heat sink. The board mounting surface of the heat sink 3 is processed so as to maintain high flatness, and the iron board 5 for mounting the light emitting element array is mounted on the board mounting surface with an adhesive having high thermal conductivity. There is.

The heat sink 3 is made of a material having a high thermal conductivity, and has a function of radiating the heat generated by the light emitting element array mounted on the iron substrate 5. The cross section of the heat sink 3 in the direction orthogonal to the longitudinal direction is generally rectangular, but as shown in FIG. 3, an opening having a U-shaped cross section is formed on the side surface of the heat sink 3 across the longitudinal ends of the heat sink 3. May be provided to increase the heat dissipation surface of the heat sink to enhance the heat dissipation effect.

The optical writing head according to the present embodiment is
The heat dissipation area of the heat sink can be expanded, the heat capacity can be increased due to the large capacity of the heat sink itself, the temperature change of the light emitting element array can be prevented in a relatively short time, and the large heat dissipation can be achieved even during continuous printing by the printer. By having an area, it is possible to reduce the steady temperature.

Next, a method of forming a wiring pattern on the iron substrate will be described. Conventionally, using a material in which a copper foil is pasted on an iron substrate through an insulator, a wiring pattern is printed on the copper foil pasting surface using a screen printing technique or the like, and then in an etching step. , The arbitrary pattern was obtained by melting the copper foil part of the non-printed part with a chemical agent. However, in this method, the accuracy of the pattern shape depends on the accuracy of the screen printing. It was difficult to form a wiring pattern.

In this embodiment, the photoresist etching method is used, and the wiring pattern is formed as follows. Laminate an insulating layer and a copper foil on an iron substrate, laminate a photosensitive dry film, expose through a photomask, develop, and then remove unnecessary portions of the copper foil by etching to form a desired wiring pattern. obtain. Also,
After printing a liquid photoresist on it and drying it,
By exposing through a photomask and developing, an insulating layer having a desired photoresist pattern is formed on the wiring pattern.

That is, since the resolution of the wiring pattern depends on the exposure photomask, a fine pattern can be formed on the iron substrate by using a highly accurate photomask. According to the photoresist etching method described above, a fine pattern with a pitch of 200 μm or less can be formed.

When a highly precise pattern shape is required, the thickness of the copper foil (pattern layer thickness) is 9 μm to 35 μm.
It is desirable to set m.

Next, points to be noted when fixing the iron substrate to the heat sink will be described. In the structure of the present invention, the influence of the substrate thickness accuracy affects the mounting surface height accuracy of the light emitting element chip. Therefore, note the following points when fixing the iron substrate to the heat sink.

The iron substrate is generally patterned in a large plate size, and is generally cut into a predetermined size by press punching in the final step, but as shown in FIG.
During press punching with the die 9 and the punch 10, burrs 8 are generated on the cut surface of the iron substrate 5. Burrs 8 on the iron substrate 5
When the iron substrate 5 is fixed to the heat sink 3 with the surface on which the bulge protrudes, the tip of the burr 8 interferes with the mounting surface of the heat sink 3 as shown in FIG. There is a problem that the accuracy is lowered. Therefore, as shown in FIG. 6, the press punching direction is set so that the direction in which the burr 8 projects is on the wiring pattern side, and the light emitting element array is mounted on the surface side on which the burr 8 of the iron substrate 5 projects. Face.

Further, the steel plate which is the base material of the iron substrate is generally cut out from a coiled material, but the thickness accuracy of the coiled material is longer in the longitudinal direction than in the widthwise direction of the coiled material. It is well known that the accuracy of is good.
FIG. 7 is a diagram for explaining the thickness accuracy of the coiled material in the width direction and the length direction. In the head structure of the present invention, since the thickness of the steel plate itself is required to have high accuracy, it is necessary to take the material of the steel plate such that the longitudinal direction of the steel plate is the longitudinal direction of the coiled material. is there. FIG. 8: is a figure explaining the material taking direction of a steel plate. When the material of the steel sheet is taken so that the longitudinal direction of the steel sheet is the width direction of the coiled material as shown by the dotted line in FIG. 8, the thickness accuracy of the coiled material is better than the lengthwise direction of the coiled material. However, since the accuracy in the width direction is poor, the accuracy of the thickness of the steel sheet itself also decreases.

The thickness of the steel sheet used in this embodiment is 0.5 to 3.0 mm, which is excellent in workability and cost.
Is desirable.

The patterned iron substrate manufactured by the above method is mounted by the following method. FIG. 9 is a diagram illustrating a method of mounting the iron substrate on the heat sink.

In this embodiment, the heat sink 3 is made of an iron material. The heat sink 3 is provided with two positioning pins 12 for positioning the iron substrate 5 at both ends in the longitudinal direction of the heat sink 3. On the iron substrate 5 side, a positioning pin insertion hole 13 is provided at a position corresponding to the position of the positioning pin 12, but one of the positioning pin insertion holes 13 provided at both ends of the iron substrate 5 is It is desirable to have a long hole shape.

After applying an adhesive to the mating surface of the heat sink 3 with the iron substrate 5, the positioning pin 12 of the heat sink 3 is fitted into the positioning pin insertion hole 13 of the iron substrate 5, and the iron substrate 5 is mounted on the heat sink 3. Install.

FIG. 10 is a sectional view for explaining a method of fixing the iron substrate to the heat sink. After attaching the iron substrate 5 to the heat sink 3, a silicon sheet 17 is sandwiched between the pressing plate 18 and the iron substrate 5 using the jig 15 shown in FIG. Hold down with the load. While being pressed down, the adhesive 19 is cured to fix the iron substrate 5 to the heat sink 3.

In order to make the light emitting element array mounting surface of the iron substrate 5 highly accurate, the light emitting element array mounting surface of the iron substrate 5 is pressed by a uniform load until the adhesive 19 hardens, and the heat sink 3 is pressed. It is necessary to follow the flatness of the mounting surface of the jig. For that purpose, an elastic body such as a silicon coat is attached to the surface of the pressing plate 16 of the jig 15 as shown in FIG. It is desirable to cure the adhesive 19 between the heat sink 3 and the iron substrate 5 while applying a load evenly.

After the iron substrate 5 is fixed by adhesion, as shown in FIG. 1, the heat sink 3 is fixed by fastening bolts 6 to the support 1 on which the erecting equal-magnification lens array 2 is mounted in advance.

FIG. 11 is a diagram showing another example of fixing the iron substrate to the heat sink. Instead of using an adhesive to fix the iron substrate and the heat sink, the iron plate 5 may be fixed to the heat sink 3 by using the pressing plate spring 21 as shown in FIG. 11, or as shown in FIG. The iron substrate 5 may be fixed to the heat sink 3 by pressing the iron substrate 5 with 22 and fastening the bolts 23.

Further, in the above-mentioned embodiment, the iron substrate is used as the substrate for mounting the light emitting element array, but instead of the iron substrate, an aluminum substrate, a stainless steel substrate, a nickel alloy substrate, a copper alloy substrate or an Invar alloy substrate is used. You may use a metal substrate, such as. The Invar alloy is
It is an alloy mainly composed of nickel and iron.

Further, it is desirable that the material of the heat sink is made of a material equivalent to that of the metal substrate or a material having an equivalent linear expansion coefficient. By configuring the heat sink with such a material, it is possible to prevent distortion of the substrate and the heat sink due to temperature change, and improve the accuracy of arranging the optical components.

In the optical writing head according to the first embodiment, since the patterning is performed on the metal substrate with high accuracy, the substrate width can be manufactured to be almost the same size as the conventional glass epoxy substrate. Even if used, it is not necessary to increase the head width.

Further, since the heat radiation area is expanded by attaching the heat sink to the metal substrate, the cooling performance of the light emitting element chip is remarkably improved without impairing the heat conduction performance of the metal substrate and the printing quality is stabilized. Can be improved.

Furthermore, if a material of the same quality as the metal substrate is used as the material of the heat sink, a difference in thermal strain does not occur between the metal substrate and the heat sink even when the temperature changes, and stress does not easily occur at the bonding interface. Assembling the heat sink and the metal substrate as an adhesive structure can reduce the assembly cost.

Next, a second embodiment of the optical writing head of the present invention will be described.

FIG. 13 is a sectional view of a second embodiment of the optical writing head of the present invention in a direction orthogonal to the head longitudinal direction. In this embodiment mode, an aluminum substrate is used as the metal substrate. The light emitting element array 34 is mounted on the aluminum substrate 33.
The erecting equal-magnification lens array 32 is arranged on the optical axis of the light emitting element of
Are fixed by an aluminum housing 31 manufactured by an aluminum die casting method. The end of the aluminum substrate 33 in the direction orthogonal to the longitudinal direction is engaged with the tip of the leg of the housing 31. In addition, the aluminum substrate 33 is pressed against the housing 31 from below the aluminum substrate 33 by the leaf spring 35, and
It is fixed at 1.

FIG. 14 is a sectional view in the longitudinal direction of the head with the leaf spring removed. On the mounting surface of the aluminum substrate 33 of the housing 31, positioning pins 36 for positioning the aluminum substrate 33 protruding from the housing 31 at both ends in the longitudinal direction of the housing 31.
Is provided. The positioning pins 36 are simultaneously formed by a die-cast manufacturing method.

FIG. 15 is a perspective view of an aluminum substrate. A positioning pin insertion hole 37 is also provided at a position corresponding to the positioning pin 36 on the aluminum substrate 33 side. By fitting the positioning pin 36 into the positioning pin insertion hole 37, the housing 31 and the aluminum substrate 33 are separated from each other. Position. As shown in FIG.
Either one of the positioning pin insertion holes 37 provided at both ends of the aluminum substrate 33 in the longitudinal direction may have a long hole shape with one end opened.

The aluminum substrate 33 is patterned in a large plate size like the iron substrate of the first embodiment,
In the final step, it is cut into a predetermined size by press punching, but burrs are generated on the cut surface of the aluminum substrate during press punching. If the tip of the burr interferes with the tip of the leg of the housing, there is a problem that the height accuracy of the light emitting element array mounting surface is lowered. for that reason,
Set the press punching direction so that the direction in which the burr of the aluminum substrate projects is not on the wiring pattern side,
The surface side of the aluminum substrate on which the burr does not project is the surface on which the light emitting element array is mounted.

Further, when the aluminum substrate is cut out from the coiled material, the accuracy in the length direction is better than that in the width direction of the coiled material. Therefore, the material is taken in the lengthwise direction of the coiled material. There is a need.

FIG. 16 is a view showing another example of fixing the aluminum substrate to the housing. As shown in FIG. 16, the aluminum substrate 33 may be fixed to the housing 31 with bolts 38.

Further, in the second embodiment, the aluminum substrate is used as the substrate for mounting the light emitting element array, but instead of the aluminum substrate, an iron substrate, a stainless steel substrate, a nickel alloy substrate, a copper alloy substrate or an Invar alloy substrate is used. You may use a metal substrate, such as.

Further, it is desirable that the material of the housing is made of a material equivalent to that of the metal substrate or a material having an equivalent linear expansion coefficient. By constructing the housing with such a material, it is possible to prevent the substrate and the housing from being distorted due to a temperature change, and to improve the accuracy of arranging the optical components.

In the optical writing head according to the second embodiment, the mechanical parts are the housing and the substrate on which the light emitting element array is mounted, and since the structure is simple, the cost can be reduced. it can. Further, since the heat of the substrate on which the light emitting element array is mounted is propagated to the housing, and the entire head serves as a heat dissipation surface, cooling of the substrate itself on which the light emitting element array is mounted is promoted.

In the first and second embodiments described above, a self-scanning light emitting element array can be used as the light emitting element array. 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 light-emitting element array, JP-A-1-238962, JP-A-2-14584, JP-A-2-92650, and JP-A-2-926.
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. 17 shows an equivalent circuit diagram of a self-scanning light emitting element array having a structure in which the shift portion and the 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, and the start pulse φ S
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 first and second embodiments described above, a rod lens array or a resin erecting equal-magnification lens array can be used as the erecting equal-magnification lens array. FIG. 18 is a cutaway perspective view showing an example of the configuration of the rod lens array. The rod lens array is an array of rod lenses 40 whose refractive index decreases from the central axis toward the periphery in one row or two rows, and can form an erecting equal-magnification image. FIG. 19 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 41 having monocular lenses 42 arranged in one or two rows, and can form an erecting equal-magnification image. The monocular lens 42 has the same focal length and aperture, and one surface is convex or both surfaces are convex.

[0066]

As described above, in the optical writing head according to the present invention, the width of the optical writing head is narrow because the metal substrate on which the wiring pattern is formed is used as the substrate on which the light emitting element chip is mounted. can do.

Further, since the metal substrate is fixed to the heat sink or the leg portion of the housing, it is possible to improve the heat radiation performance of the light emitting element and to manufacture the optical writing head capable of obtaining a high quality printed image.

[Brief description of drawings]

FIG. 1 is a sectional view of a conventional optical writing head in a direction orthogonal to a head longitudinal direction.

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

FIG. 3 is a perspective view showing a state where an iron substrate is attached to a heat sink.

FIG. 4 is a diagram showing a state in which burrs are generated on a cut surface of an iron substrate during press punching.

FIG. 5 is a diagram showing a state in which the tip of the burr interferes with the mounting surface of the heat sink.

FIG. 6 is a diagram showing a state in which an iron substrate is placed on a heat sink so that the direction in which burrs project is the pattern side.

FIG. 7 is a diagram for explaining the thickness accuracy of the coiled material in the width direction and the length direction.

FIG. 8 is a diagram illustrating a material taking direction of a steel plate.

FIG. 9 is a diagram illustrating a method of mounting an iron substrate on a heat sink.

FIG. 10 is a cross-sectional view for explaining a method of fixing an iron substrate to a heat sink with a jig.

FIG. 11 is a diagram showing another example of fixing an iron substrate to a heat sink.

FIG. 12 is a diagram showing another example of fixing the iron substrate to the heat sink.

FIG. 13 is a cross-sectional view showing a second embodiment of an optical writing head of the present invention in a direction orthogonal to the head longitudinal direction.

FIG. 14 is a cross-sectional view in the longitudinal direction of the head with a leaf spring removed.

FIG. 15 is a perspective view of an aluminum substrate.

FIG. 16 is a diagram showing another example of fixing the aluminum substrate to the housing.

FIG. 17 is a diagram showing an equivalent circuit of a self-scanning light emitting element array.

FIG. 18 is a cutaway perspective view showing an example of the configuration of a rod lens array.

FIG. 19 is a perspective view showing an example of the configuration of a resin erecting equal-magnification lens array.

[Explanation of symbols]

1 support 2,32,51 Erect equal-magnification lens array 3 heat sink 4,34 Light emitting element array 5 iron substrate 6,23,38 bolt 8 Bali 9 dice 10 punches 12,36 Positioning pin 13,37 Positioning pin insertion hole 15 jigs 16 air cylinders 17 Silicon Sheet 18 Hold plate 19 adhesive 21 Press leaf spring 22 Press plate 31 housing 33 Aluminum substrate 35 leaf spring 40 rod lens 41 lens array plate 42 monocular lens 52 Tree branch cover 53 substrates 54 Light emitting element chip 55 Photosensitive drum

Claims (13)

[Claims] 1. An optical writing head for condensing light emitted from a light emitting element array having light emitting elements arranged in a row by a lens array having lenses arranged in a row and projecting the light onto a photoconductor. Is mounted on a metal substrate having a wiring pattern formed thereon, and the metal substrate is fixed to a heat sink for radiating heat from the light emitting element array. 2. The optical writing head according to claim 1, wherein the metal substrate has a surface on which a burr generated at the time of manufacturing the substrate protrudes as a surface on which the light emitting element array is mounted. 3. The optical writing head according to claim 1, wherein the heat sink is made of a material equivalent to the metal substrate or a material having an equivalent linear expansion coefficient. 4. The heat sink is provided with alignment pins at least at both ends in the longitudinal direction of the heat sink, and the metal substrate is provided with alignment pin insertion holes at positions corresponding to the alignment pins. The metal substrate is aligned and fixed to the heat sink by inserting and fitting the alignment pin into a pin insertion hole. Optical writing head. 5. An optical writing head for condensing light emitted from a light emitting element array having light emitting elements arranged in a row by a lens array having lenses arranged in a row and projecting the light onto a photosensitive member. Is mounted on a metal substrate on which a wiring pattern is formed, and the metal substrate is engaged with and fixed to a leg portion of a housing supporting the lens array. 6. The optical writing head according to claim 5, wherein the metal substrate has a surface on which a burr generated at the time of manufacturing the substrate does not project as a surface on which the light emitting element array is mounted. 7. The optical writing head according to claim 5, wherein the housing is made of a material equivalent to that of the metal substrate or a material having an equivalent linear expansion coefficient. 8. The housing is provided with alignment pins at least at both ends in the longitudinal direction of the housing, and the metal substrate is provided with alignment pin insertion holes at positions corresponding to the alignment pins. The metal substrate is aligned and fixed to the housing by inserting and fitting the alignment pin into a pin insertion hole. Optical writing head. 9. The metal substrate is made of a coiled material so that the longitudinal direction of the metal substrate is the lengthwise direction of the coiled material.
8. The optical writing head according to any one of 8. 10. The optical writing according to claim 1, wherein the metal substrate is an iron substrate, an aluminum substrate, a stainless substrate, a nickel alloy substrate, a copper alloy substrate or an Invar alloy substrate. head. 11. The optical writing head according to claim 1, wherein the wiring pattern is formed by a photoresist etching method. 12. 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. 13. The optical writing head according to claim 1, wherein the light emitting element array is a self-scanning type light emitting element array.