JPH11227248A - Minute reflection optical element array - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a minute reflecting optical element array which does not deteriorate image quality as a result of influences of a light from other than an original emission area and appropriate for use in high-resolution optical write. SOLUTION: A minute reflecting optical element array 11 is incorporated in an optical write apparatus having a light-emitting element array 7 of a plurality of light-emitting elements 2 arranged linearly on a substrate 4 and controlled individually tom emit light. The minute reflecting optical element array 11 arranged near the light-emitting element array 7 has opening parts 13 formed linearly on an optical element substrate 12 to correspond to the light-emitting elements 2 with having an in-plane section tapering towards the light-emitting element array 7. An original light P1 emitted from each light-emitting element 2 is guided in an original direction through the corresponding opening part 13 and moreover, lights P2, P3 from other than an original emission area are reflected at a surface of the opening part 13 towards the original direction and consequently do not become a stray light.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a micro-reflection optical element array used in an optical writing device such as an LED array printer utilizing an electrophotographic process.

[0002]

2. Description of the Related Art With the development of information devices for office use and personal use in recent years, demand for higher resolution, compact and inexpensive printers using an electrophotographic process is increasing. As an example of a device satisfying such a requirement, for example, a large number of minute L
There is an LED array printer using an LED array head in which ED light emitting elements are arranged in an array on a substrate. According to such an LED array printer, since it is a solid-state scanning type using an LED array head as a writing light source, the device is smaller in size than a laser printer or the like using a raster scanning type writing optical system using a semiconductor laser. In addition, since each LED light emitting element of the LED array head writes data in parallel, high-speed output can be achieved relatively easily.

A configuration example of an LED array head used in such an LED array printer is disclosed in, for example,
-125114. 1 is LE
L on which the D light emitting element 2, the bonding pad 3, etc. are formed
The ED array chip is mounted on the substrate 4 together with a driver IC (not shown) and the like. A current is supplied to the bonding pads 3 on the LED array chip 1 via bonding wires 6 connected between the bonding pads 3 and the substrate-side bonding pads 5. LE
In the D array chip 1, the LED light emitting element 2 and the bonding pad 3 are connected by a wiring pattern (not shown). The light emitted from the selected LED light emitting element 2 in the LED array head 7 is condensed and irradiated on the surface of the drum-shaped photosensitive member 9 via the same-magnification image forming optical system 8 to expose the photosensitive surface. As a result, an electrostatic latent image is formed. As the unit-magnification imaging optical system 8, a lens array using a gradient index fiber is generally used.

[0004]

In such an LED array head 7, there is light incident on the same-magnification imaging optical system 8 from a place other than the original light-emitting area, which degrades image quality. Cause. For example, a part of the emitted light is reflected by the bonding wire 6 as shown in FIG. 4 and enters the viewing angle θ of the unity-magnification imaging optical system 8 as light from a region other than the LED light emitting element 2, There is a problem that the image quality is degraded by being irradiated as unnecessary light spots or stray light on the nine surfaces. In addition,
A region on the substrate 4 which should not emit light may emit light due to an abnormality in a manufacturing process or the like. In this regard, since the LED array printer using the LED array head as a writing light source originally had a device with a relatively low resolution of about 400 dpi, the influence of such stray light was not a serious problem. Then 60
Devices with a high resolution of 0 to 1200 dpi have been realized, and can no longer be ignored as one of the factors that degrade the image quality.

[0005] Incidentally, as a method for preventing image quality from being degraded by light from an area other than the LED light emitting element,
Japanese Patent Application Laid-Open No. 4-179558 discloses a method of covering all areas other than LED light emitting elements with a paint exhibiting a light shielding effect. If this method is applied to a bonding wire, it is possible to reduce the reflected light at this portion. However, even the surface of the light-shielding paint has a slight reflectance, so that the reflected light at this portion cannot be completely eliminated. Such slight reflected light on the surface of the light-shielding paint is not particularly problematic in the case of the conventional low-resolution LED array printer, but is very weak in recent high-resolution LED array printers. Even stray light has a non-negligible effect on the image and degrades image quality. Therefore, the method of preventing the influence of the reflected light by the light-shielding paint is insufficient. Also, even if this method is effective, if you use it for a long time,
This type of paint has a limited weather resistance, so the surface of the light-shielding paint ages and becomes rough, and as a result, it becomes whitish, the reflectance gradually increases, and the desired effect cannot be obtained. It is.

Therefore, the present invention is suitable for optical writing of a high-resolution image forming apparatus without being affected by light from a region other than the original light-emitting region and deteriorating image quality. It is an object of the present invention to provide a miniature reflective optical element array.

[0007]

According to the first aspect of the present invention,
It is incorporated in an optical writing device having a light emitting element array having a plurality of light emitting elements which are formed in a linear array on a substrate and each of which is individually controlled to emit light, and is arranged close to the light emitting element array. A micro-reflection optical element array, in which an in-plane cross-sectional shape of the optical element substrate is tapered on the side of the light-emitting element array to form a tapered opening corresponding to each of the light-emitting elements. Have been.

Accordingly, the original light emitted from each light emitting element passes through the corresponding opening and goes in the original direction, and the light generated from the area other than the original light emitting area due to reflection on the light emitting element array side surface or the like. Even if the light is reflected on the surface of the opening, the light can be guided in the same direction as the original light, does not become irregular stray light, and does not adversely affect the written image.

According to a second aspect of the present invention, there is provided the micro-reflection optical element array according to the first aspect, wherein an escape recess formed on the surface of the optical element substrate on the light emitting element array side corresponding to the shape of the wiring portion on the light emitting element array. Are formed.

The micro-reflection optical element array is mounted on the light-emitting element array at a suitable interval or in close contact with the light-emitting element array by, for example, bonding with an ultraviolet curable resin or the like. At this time, depending on the configuration of the light emitting element array side, a wiring pattern may be provided immediately adjacent to the light emitting area, and the step of the wiring pattern may hinder the mounting of the minute reflection optical element array, and the ultraviolet curing Since the thickness of the adhesive layer such as resin is large, there is a concern that the accuracy of the mounting position may be reduced in the manufacturing process or the time required for the positioning may be long. In this regard, since the escape recess corresponding to the shape of the wiring portion on the light emitting element array is formed on the surface of the optical element substrate on the light emitting element array side, the light emitting element array is not affected by the wiring portion. Can be implemented.

According to a third aspect of the present invention, in the micro-reflection optical element array according to the first or second aspect, the surface of the opening is selected from aluminum, titanium, gold, silver, tungsten, nickel, and chromium. The reflective layer is formed by a thin film of the above metal material or a laminate of these thin films.

Accordingly, the original light emitted from each light emitting element passes through the corresponding opening and goes in the original direction, and the light is emitted from an area other than the original light emitting area due to reflection on the light emitting element array side surface. Light directed toward the surface of the part can be reliably guided in the same direction as the original light by the reflecting layer of a predetermined material formed on this surface, and the light is effectively guided to the unity imaging optical system and the like. Since the writing light amount increases, higher-speed writing can be achieved. Alternatively, since the brightness of the image is increased by increasing the writing light amount, there is also obtained an advantage that a photosensitive member having a lower sensitivity can be used.

[0013]

FIG. 1 shows a first embodiment of the present invention.
A description will be given based on FIG. The micro-reflection optical element array 11 of the present embodiment is, for example, an LE having the configuration shown in FIG.
This is used by being superposed on the substrate 4 of the LED array head 7 in the D array printer. In the micro-reflection optical element array 11, the optical element substrate 12 has a polygonal cross section in an in-plane direction, for example, a quadrangle (or a circle).
In this configuration, the tapered openings 13 tapering on the substrate 4 side are formed in a straight line and formed through. Here, the size and pitch of such an opening 13 are the size of each LED light emitting element 2 which is a light emitting element on the LED array chip 1,
It is formed so as to match or almost match the pitch.
The reflection layer 14 is formed on the surface of the opening 13. The reflective layer 14 may be made of a metal material,
Among various materials that can be used industrially by the inventor, according to the results of evaluation of compatibility by experiments,
It has been found that a thin film of any metal material selected from titanium, gold, silver, tungsten, nickel and chromium or a laminate of these thin films is preferable.
The optical element substrate 12 is preferably made of a material that is opaque to the light emitted from the LED light emitting element 2. 12 itself may be made of a transparent material, which gives a wider choice of materials.

Such a micro-reflection optical element array 11 must be mounted on the LED array chip 1 with a suitable space or close contact with the LED array chip 1, as shown in FIG. Thereby constitute a part of the LED array head 7.

According to the LED array head 7 having such a micro-reflection optical element array 11, the original light P 1 emitted from each LED light-emitting element 2 is transmitted to the corresponding aperture 13.
It passes through the inside and heads in the original direction of the 1 × imaging optical system or the like. Further, even if there is light P2 or P3 emitted from a portion other than the light emitting area of the LED light emitting element 2 and reflected on the surface, such light P2 or P3 is transmitted through the opening 13
And the light can be guided in the same direction as the original light P1. Therefore, the light P2 and P3 do not become irregular stray light, and do not adversely affect the written image unlike the conventional countermeasure using the light-shielding paint.
In particular, in the case of the present embodiment, since the reflection layer 14 is formed on the surface of the opening 13, the light P2 and P3 are
1 can be reliably and efficiently guided in the same direction as 1, and can be effectively incident on the corresponding 1 × imaging optical system. As a result, light contributing to image formation is increased, and the brightness of the image is increased, so that a photosensitive member 9 having a lower sensitivity can be used or optical writing can be performed at a higher speed.

Here, an example of a specific configuration example will be described. First, a micro-reflection optical element array 11 having a structure as shown in FIG. 2 was manufactured. The quartz glass substrate (optical element substrate 12) was polished to a thickness of 40 μm, attached to a flat glass plate (not shown) with a thermoplastic resin, and a photoresist was applied on the quartz glass substrate. OFPR8600 manufactured by Tokyo Ohka Co., Ltd. was used as the photoresist, and the photoresist was applied by spin coating so as to have a thickness of 3 μm. A pattern in which a circular opening pattern having a diameter of 20 μm is linearly arranged at a pitch of 40 μm (corresponding to 600 dpi) is baked on the photoresist, and a normal developing process is performed.
A rinsing step was performed to form a resist mask in which columns having the same shape were arranged. Therefore, the back surface and the periphery were masked so that the glass plate serving as the base was not attacked by the etching solution, and etching was performed in a dilute hydrofluoric acid solution. The etching time was determined by observing the point in time when the quartz glass substrate penetrated and the base glass plate was exposed. In this case, utilizing the fact that the diameter of the upper portion is enlarged by the undercut, a micro-reflection optical system in which tapered openings 13 having an upper diameter of 30 μm and a lower diameter of 20 μm are linearly arranged at a pitch of 40 μm. An element array 11 was obtained. The taper shape was controlled by adjusting the temperature of the etchant, the concentration of hydrofluoric acid, and the frequency of stirring. Next, the etching mask was removed while being attached to the glass plate serving as the base, and one surface of the quartz glass substrate (the diameter of the opening 13 was 2 mm) was removed by a vacuum evaporation apparatus.
Gold (Au) is vapor-deposited to a thickness of 7000 mm on the surface side (0 μm), and then the glass plate is heated and removed from the quartz glass substrate. The micro-reflection optical element array 11 on which the reflection layer 14 was formed was completed by removing the used thermoplastic resin.

An optical writing device as shown in FIG. 4 was manufactured in order to examine the function of such a minute reflection optical element array 11. Here, SLA12D manufactured by Nippon Sheet Glass Co., Ltd. was used as the 1 × imaging optical system 8. As for the LED array head 7, a PN junction is formed by growing a gallium arsenide crystal layer on a silicon wafer (substrate 4) by a heteroepitaxial method and diffusing zinc (Zn) into the gallium arsenide crystal layer. The gallium arsenide crystal layer is 10 μm × 10
40μm pitch (equivalent to 600dpi)
By patterning so that it is arranged in a straight line,
Many LED light emitting elements 2 were formed in an array. Subsequently, a silicon oxide film is deposited as an insulating film to a thickness of 5000 ° on the entire surface of such an element, a contact hole is formed, a wiring pattern is formed on the LED light emitting element 2 with aluminum, and bonding is performed on the end thereof. Pad 3 was formed. More specifically, a wiring pattern is drawn out on both left and right sides orthogonal to the array direction with the LED light emitting element 2 as a center, and approximately 300 μm from the light emitting area of the LED light emitting element 2.
The bonding pad 3 was disposed at a position m away from the substrate, and a bonding wire 6 was connected between the bonding pad 3 and the substrate-side bonding pad 5. The bonding wire 6 has a wire diameter of 18
A μm gold wire was used. Next, the micro-reflection optical element array 11 manufactured as described above is cut into a strip shape by a dicing saw to a width smaller than the interval between the bonding pads 3, and is aligned with the LED light-emitting element 2 on the LED array chip 1 to be cured with an ultraviolet curable resin. Thus, an LED array head 7 having a structure as shown in FIG. 1 was completed.

In the comparative example, as in the specific example, L
Although the ED array head 7 is formed, a conventional structure example without the micro-reflection optical element array 11 is used. And LED
The light-emitting element 2 was configured so that a portion outside the light-emitting region was covered with a black light-shielding paint.

The LEs of these specific configuration examples and comparative configuration examples
An electrostatic latent image is formed on the photoreceptor 9 using a D array head, and the image quality is evaluated by attaching toner (the shape of the light emitting layer area of the LED light emitting element 2 is transferred well and an unnecessary pattern is generated. Those that were not evaluated were evaluated as “suitable”, and those in which the shape of the light-emitting layer region was significantly deformed or an unnecessary pattern was evaluated were evaluated as “unsuitable”. Immediately after or after the environmental resistance test (environmental resistance test of temperature cycle to reproduce the situation after long-term use), the evaluation was “suitable” in any case. The evaluation was also “unsuitable”. Thereby, according to the present embodiment,
Even in a high-resolution configuration of 600 dpi, the LED array head 7 has no deterioration in image quality due to stray light reflected from the bonding wire 6 and unnecessary light from a portion other than the light emitting region. It can be seen that the performance can be maintained over a period of time. In addition, since the reflection layer 14 is formed on the surface of the opening 13, the amount of light effectively entering the unit-magnification imaging optical system 8 increases, and the amount of exposure to the photoconductor 9 increases, so that the writing speed also increases. It was something that could be done.

Another specific configuration example will be described. In this specific configuration example, instead of the quartz glass substrate,
Using a soda glass substrate (optical element substrate 12) colored dark brown by adding a metal salt, a micro-reflection optical element array 11 similar to the specific configuration example described above was produced. However,
In this specific configuration example, the reflection layer 14 is not formed.

An optical writing apparatus as shown in FIG. 4 was manufactured in order to examine the function of such a micro-reflection optical element array 11. Here, SLA12D manufactured by Nippon Sheet Glass Co., Ltd. was used as the 1 × imaging optical system 8. As for the LED array head 7, a PN junction is formed by growing a gallium arsenide crystal layer on a silicon wafer (substrate 4) by a heteroepitaxial method and diffusing zinc (Zn) into the gallium arsenide crystal layer. The gallium arsenide crystal layer is 10 μm × 10
40μm pitch (equivalent to 600dpi)
By patterning so that it is arranged in a straight line,
Many LED light emitting elements 2 were formed in an array. Subsequently, a silicon oxide film is deposited as an insulating film to a thickness of 5000 ° on the entire surface of such an element, a contact hole is formed, a wiring pattern is formed on the LED light emitting element 2 with aluminum, and bonding is performed on the end thereof. Pad 3 was formed. More specifically, a wiring pattern is drawn out on both left and right sides orthogonal to the array direction with the LED light emitting element 2 as a center, and approximately 300 μm from the light emitting area of the LED light emitting element 2.
The bonding pad 3 was disposed at a position m away from the substrate, and a bonding wire 6 was connected between the bonding pad 3 and the substrate-side bonding pad 5. The bonding wire 6 has a wire diameter of 18
A μm gold wire was used. Next, the micro-reflection optical element array 11 manufactured as described above is cut into a strip shape by a dicing saw to a width smaller than the interval between the bonding pads 3, and is aligned with the LED light-emitting element 2 on the LED array chip 1 to be cured with an ultraviolet curable resin. To complete the LED array head 7.

In the comparative example, as in the specific example, L
Although the ED array head 7 is formed, a conventional structure example without the micro-reflection optical element array 11 is used. And LED
The light-emitting element 2 was configured so that a portion outside the light-emitting region was covered with a black light-shielding paint.

The LEs of these specific configuration examples and comparative configuration examples
An electrostatic latent image was formed on the photoreceptor 9 using a D array head, and the image quality was evaluated by attaching toner. In the case of the above specific configuration example, the electrostatic latent image was obtained immediately after production or after an environmental resistance test. In each case, the evaluation was “suitable”, but in the comparative configuration example, the evaluation in each case was “unsuitable”. As a result, even in a high-resolution configuration of 600 dpi, the LED array head 7 does not suffer from deterioration in image quality due to reflected light from the bonding wire 6 and unnecessary light from a portion other than the light emitting region becoming stray light. It can be seen that the performance can be maintained for a long time. Further, in the case of this specific configuration example, the writing speed could not be improved because the reflective layer 14 was not provided. However, since the reflective layer 14 was not formed, the device was manufactured at a lower cost than the specific configuration example described above. Was made.

A second embodiment of the present invention will be described with reference to FIG. In the present embodiment, a relief recess 15 is formed on the surface of the optical element substrate 12 on the substrate 4 side with respect to the minute reflection optical element array 11. These escape recesses 15 are formed corresponding to the position, height, and the like of the wiring portion 16 so as to escape the wiring portion 16 formed on the substrate 4 side.

The micro-reflection optical element array 11 is mounted on the substrate 4 at an appropriate interval or in close contact with the substrate 4 by a method such as bonding with an ultraviolet curable resin or the like. On this occasion,
Depending on the configuration of the LED array head 7 side, as shown in FIG. 3, a wiring portion 16 such as a wiring pattern may be provided in an asymmetric shape at a position immediately adjacent to the light emitting region of the LED light emitting element 2. In this case, the step of the wiring portion 16 hinders the mounting of the micro-reflection optical element array 11, and the thickness of the adhesive layer such as an ultraviolet curable resin is large, so that the accuracy of the mounting position is reduced in the manufacturing process or required for alignment. There is a concern that the time will be longer. In this regard, according to the present embodiment, the wiring unit 1
Since the escape recess 15 is formed corresponding to the shape of 6, the micro-reflection optical element array 11 can be mounted on the substrate 4 without being affected by the wiring section 16.

A specific configuration example in the case of the present embodiment will be described. In this specific configuration example, with respect to the micro-reflection optical element array 11 according to any specific configuration example of the above-described embodiment, the wiring portion 1 is provided on the back surface side of the optical element substrate 12.
The escape recess 15 corresponding to No. 6 was formed by forming an etching mask by photolithography and etching with dilute hydrofluoric acid. The rest is the same as the specific configuration example described above.

According to the micro-reflection optical element array 11 in which such a recess 15 is formed, even if the wiring section 16 as shown in FIG. Reflective optical element array 1
1 can be mounted, positioning is completed in a short time,
This does not lead to an increase in manufacturing cost.

[0028]

According to the first aspect of the present invention, there is provided an optical writing apparatus including a light emitting element array having a plurality of light emitting elements which are formed in a linear array on a substrate and each of which is individually controlled to emit light. And a micro-reflection optical element array which is disposed in close proximity to the light-emitting element array, and the light-emitting element array side has a tapered opening in the optical element substrate. Since they are formed in a linear array corresponding to the elements, the original light emitted from each light emitting element can pass through the corresponding opening and be directed in the original direction, and the light emitting element array Even if there is light generated from other than the original light emitting area due to reflection on the side surface, etc., the light can be guided in the same direction as the original light by being reflected on the surface of the opening, thereby causing irregular stray light. Is nothing , It is possible to prevent an adverse effect on the written image.

According to the second aspect of the present invention, in the micro-reflection optical element array according to the first aspect, the surface of the optical element substrate on the light emitting element array side is made to correspond to the shape of the wiring portion on the light emitting element array. Since the escape recess is formed, a wiring pattern may be provided at a position immediately adjacent to the light emitting region depending on the configuration of the light emitting element array side, but the wiring pattern is not affected by the wiring portion on the light emitting element array. Can be implemented.

According to a third aspect of the present invention, in the micro-reflection optical element array according to the first or second aspect, aluminum, titanium, gold, silver, tungsten,
Since the reflection layer is formed by a thin film of any metal material selected from nickel or chromium or a laminated body of these thin films, it is generated from a region other than the original light emitting region due to reflection on the light emitting element array side surface or the like. Light directed toward the surface of the opening can be reliably and efficiently guided in the same direction as the original light by the reflective layer of a predetermined material formed on the surface, and the light is effectively guided to the 1 × imaging optical system and the like. By increasing the amount of writing, the amount of writing light can be increased, so that higher-speed writing can be achieved, and the brightness of an image can be increased by increasing the amount of writing light, so that a photosensitive member with lower sensitivity can be used. And other advantages.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a first embodiment of the present invention.

FIG. 2 is a perspective view showing a minute reflection optical element array alone.

FIG. 3 is a sectional view showing a second embodiment of the present invention.

FIG. 4 is a schematic side view showing a conventional example.

[Explanation of symbols]

 Reference Signs List 2 light emitting element 4 substrate 7 light emitting element array 12 optical element substrate 13 opening 14 reflection layer 15 escape recess 16 wiring section

Claims (3)

[Claims] 1. A light-emitting device including a light-emitting element array having a plurality of light-emitting elements formed in a straight line on a substrate and individually controlled for light emission, and incorporated in an optical writing device. A micro-reflection optical element array arranged in such a manner that an in-plane cross-sectional shape of the optical element substrate is tapered toward the light-emitting element array side and an opening is formed in a straight line corresponding to each of the light-emitting elements. A micro-reflection optical element array characterized by being formed in a matrix. 2. The micro-reflection optics according to claim 1, wherein an escape recess corresponding to the shape of the wiring portion on the light-emitting element array is formed on the surface of the optical element substrate on the light-emitting element array side. Element array. 3. An aluminum, titanium,
3. The microreflection according to claim 1, wherein the reflection layer is formed by a thin film of any metal material selected from gold, silver, tungsten, nickel and chromium, or a laminate of these thin films. Optical element array.