JPH10193679A - Laser light source device and laser printer - Google Patents

Abstract

(57) [Summary] To provide a laser printer capable of stably realizing high-speed printing at high speed. A laser light source device using a laser chip having a laminated structure in which a laminated portion of a gallium nitride based semiconductor emits light at a wavelength of 550 nm or less is scanned and exposed to a photosensitive member having high sensitivity at a wavelength of 550 nm or less. Then, the wavelength of the exposure light and the wavelength of the sensitivity of the photoconductor are matched to realize high-speed, high-quality, stable electrophotographic printing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser light source device and a laser printer using the light source device.

[0002]

2. Description of the Related Art With the advance of the advanced information age, further speeding up of printing technology is required. A laser printer is suitable for high-speed printing, but in order to achieve high speed,
It is necessary to match the following two conditions.

[0003] First, the use of a photoreceptor having a high photosensitivity and a long life shortens the irradiation time per bit, ie,
The purpose is to increase the speed of exposure scanning and lengthen the period of changing the photoconductor, and secondly, to use a short wavelength laser light source.

In a laser printer, a laser beam for exposing a photoreceptor is irradiated on a reflection surface of a rotating polygon mirror (hereinafter, referred to as a polygon mirror), and is deflected and scanned by rotation of the polygon mirror to form a drum on which a photoreceptor layer is formed. The light is condensed by the fθ lens so as to form the same beam waist diameter (hereinafter, referred to as a spot diameter) on the upper side. At this time, the scanning speed is proportional to the product of the number of rotations of the polygon mirror and the number of reflection surfaces per rotation. Here, the spot diameter must always be constant in order to correspond to the resolution. In addition, the size and the number of rotations of the polygon mirror are limited by the specifications of the device and are constant.

Therefore, in order to achieve high speed, it is necessary to increase the number of reflecting surfaces per one rotation of the polygon mirror. If the size of the polygon mirror is fixed, the reflection surface becomes small in order to increase the number of surfaces per rotation, so that it is necessary to reduce the beam diameter. Here, the spot diameter is obtained by (wavelength) / (lens numerical aperture). As the beam diameter decreases, the numerical aperture of the lens decreases and the spot diameter increases. Therefore, in order to obtain the same spot diameter, it is necessary to shorten the wavelength of the laser beam. For these reasons, in order to increase the speed, it is necessary to shorten the wavelength of the laser beam. In order to match the first condition and the second condition, it is necessary to use a photoconductor having a high spectral sensitivity characteristic at a relatively short wavelength. At present, combinations that satisfy the above conditions include selenium and a selenium photoreceptor having a spectral sensitivity characteristic peak at a wavelength near 400 nm, a He-Cd laser having an oscillation wavelength of 442 nm, and a 488 nm
Ar lasers have been commercialized.

[0006]

The gas laser light source device such as the He-Cd laser or the Ar laser described above has the following problems.

First, because the laser medium is a gas,
There was a decrease in output due to outgassing and the like, and it was difficult to obtain a light source that could achieve the long life required for the device.

[0008] Second, in order to obtain a sufficient light emission output, a discharge by a high voltage power supply is necessary, and the power consumption is significantly increased.

Third, there is a drift in the output fluctuation at the initial stage of operation until the discharge is stabilized or in a long-time operation.

Fourth, the volume of the gas tube and the volume of the power supply are large, which hinders downsizing of the laser printer.

Fifth, since the peak of the spectral sensitivity of selenium and a selenium-based photoreceptor generally exists near 400 nm, the deviation from the oscillation wavelength of a gas laser is large. Therefore, a laser light source device having a short oscillation wavelength of several tens of nm was required.

An object of the present invention is to provide a laser printer capable of stably realizing high-speed, high-quality printing. More specifically, in an electrophotographic laser printer that forms a latent image by scanning and exposing a photoconductor using a laser beam emitted from a semiconductor laser light source device, an optimum configuration of the semiconductor laser light source device and the photoconductor is used. An object of the present invention is to stably realize high-speed and high-quality printing by a combination.

Another object of the present invention is to provide a laser light source device capable of stably emitting a laser beam from a plurality of light emitting units. More specifically, an object is to stably generate a plurality of laser beams by a semiconductor laser chip array with a control circuit having a simple configuration.

[0014]

SUMMARY OF THE INVENTION A laser printer according to the present invention includes a laser light source device and a photoconductor on which a latent image is formed by being exposed to a laser beam emitted from the laser light source device through an optical system. In the electrophotographic laser printer provided, the laser light source device uses a laser chip having a laminated structure that emits light at a wavelength of 550 nm or less in the laminated portion of the gallium nitride based semiconductor, and the photoconductor has a wavelength of 550 nm or less. With high sensitivity, high-speed and high-quality stable printing can be realized.

A laser printer according to the present invention includes a laser light source device which is controlled to blink in accordance with print information, and a laser beam emitted from the laser light source device which is condensed and irradiated on a photosensitive member while being deflected by a rotary polygon mirror. An electrophotographic laser printer comprising an optical system for forming a latent image on the photoreceptor, wherein the laser light source device has a laminated structure in which a laminated portion of a gallium nitride based semiconductor emits light at a wavelength of 550 nm or less. Using a chip, the optical system is such that the laser beam is deflected by being reflected by a rotary polygon mirror in a substantially parallel light state, and the photoconductor has a sensitivity peak at a wavelength of 550 nm or less. Thus, high-speed, high-quality, stable printing is realized.

The laser light source device incorporates a plurality of laser chips having a stacked structure of a gallium nitride-based semiconductor in a stacked structure that emits light at a wavelength of 550 nm or less in a juxtaposed state. By configuring such that the laser beams emitted from the individual laser chips are collectively deflected and irradiated onto the photoreceptor, it is possible to further increase the speed by multi-exposure.

Further, the laser light source device of the present invention comprises a plurality of laser chips having a laminated structure in which a laminated portion of a gallium nitride based semiconductor emits light at a wavelength of 550 nm or less, and one light emission common to the plurality of laser chips. By incorporating the quantity detection element in one package, control for stably emitting a laser beam from a plurality of light emitting units is simplified.

By arranging a separate light emitting amount detecting element for each of the plurality of laser chips, the light emitting amount of each laser chip can be detected in parallel in real time.

In the present invention, concrete measures for solving the conventional problems are as follows. First, longer life was achieved by solidifying all laser components, including the laser medium.

Second, the improvement in efficiency and the remarkable reduction in power consumption have been achieved by using a GaN-based medium as a laser medium to realize a semiconductor laser light source having an oscillation wavelength of 550 nm or less, particularly near 400 nm. .

Third, output stabilization with a simple laser control circuit configuration has been achieved by using a GaN-based semiconductor laser chip that is environmentally stable as a light source.

Fourth, a significant reduction in volume was achieved by downsizing using the GaN-based semiconductor laser chip described above. In particular, a short-wavelength laser beam obtained by a GaN-based semiconductor laser chip is advantageous in miniaturizing a deflection scanning optical system.

Fifth, to further increase the speed, the laser light source is shifted to the peak wavelength of the spectral sensitivity of the photosensitive member by utilizing the fact that the oscillation wavelength of the GaN-based semiconductor laser chip can be easily set in a wide range at the time of manufacturing. Were achieved by matching the wavelengths of the two.

[0024]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a perspective view showing a first embodiment of a scanning exposure system 100 in a laser printer according to the present invention.

The laser light source device 101 incorporating a GaN-based semiconductor laser chip emits a short-wavelength laser beam under the control of the optical system controller 1000. Laser light source device 10
1 emits a laser beam from a collimating lens 10
2, the light is made substantially parallel light, passes through a cylindrical lens 103 which has power only in the sub-scanning direction and forms an image on the reflection surface of the polygon mirror 104 in the sub-scanning direction, is reflected by the polygon mirror 104, and is further reflected by the fθ lens 105.
Irradiation is performed so as to form a uniform spot on the surface of the Se-based photosensitive drum 106. The target latent image is turned on / off of the drive current of the GaN-based semiconductor laser chip of the laser light source device 101.
It is formed by intermittent light emission due to OFF modulation, deflection scanning by rotation of the polygon mirror 104 at a constant speed, and rotation of the photosensitive drum 106. The on / off modulation of the drive current is performed by the image signal 108 generated by the printer central control unit 2000 based on the print information created by the upper information processing apparatus 3000.
Is performed by the optical system control unit 1000 according to the following.

A beam detector (hereinafter abbreviated as BD) sensor 107 is provided to detect an accurate writing start timing for each line. This BD sensor 107
Generates a line synchronization signal 109 when irradiated with a laser beam during deflection scanning. The optical system controller 1000 controls the photosensitive drum 10 based on the line synchronization signal 109.
6 to obtain the timing of starting writing of the image signal 108 for each line to the printer central control unit 2000.

In order to achieve a high-speed and high-definition laser printer, it is necessary to match the above two conditions. First, a short wavelength laser beam is used. Second, the use of a photosensitive drum having high photosensitivity and a long life shortens the irradiation time per bit, that is, increases the deflection scanning speed and lengthens the photoconductor drum replacement cycle.

Here, a gallium nitride-based compound semiconductor (GaN-based semiconductor) laser chip realizes the laser light source device 101 that generates a short-wavelength laser beam satisfying the first condition. GaN-based semiconductor laser chips are III-V
It is made of a group III material and is composed of at least one group III element such as Ga, In, and Al and at least one group V element such as N, P, As, and Sb. Depending on
It is doped with impurities such as group II Mg, Zn, Cd.
The first advantage of the III-V group medium is that the medium is stable against the environment. Therefore, a semiconductor laser chip using these can simplify the drive control circuit.
You can aim for lower prices. The second advantage is that the emission wavelength of the GaN-based semiconductor laser chip can be freely set by adjusting the band gap. Specifically, the band gap of GaN is 3.4 eV, but the band gap energy is set to 2.0 eV by forming a mixed crystal with InN (band gap = 2.0 eV) or AlN (6.3 eV).
From about 6.3 eV to about 6.3 eV, and the emission wavelength can be arbitrarily set within a wide range from ultraviolet to green. Optimal design is possible in view of the chromatic aberration of the lens used in the deflection scanning optical system and the wavelength separation performance of the dichroic mirror. A third advantage is that a GaN-based semiconductor laser chip emits light at a short wavelength, and is therefore suitable for realizing a printer corresponding to the recent trend toward higher resolution.

The second condition, that is, a photosensitive drum having a high sensitivity and a long life is realized by the Se photosensitive drum 106 having a spectral sensitivity characteristic peak at a wavelength near 400 nm.
It is.

The laser printer according to the present invention is configured as an electrophotographic printer in which the laser light source device 101 using such a GaN-based semiconductor laser chip and the Se-based photosensitive drum 106 are combined. The electrophotographic printer includes a process of charging, exposing, and developing the photosensitive drum 106, a process of transferring and fixing the toner image formed on the photosensitive drum 106 to recording paper, and a process of transferring the toner image to the photosensitive drum. Erase to body drum 106,
Perform the cleaning process. The Se-based photoconductor drum 106 has a photosensitive layer of a Se-based photoconductor formed on the outer peripheral surface of a conductive drum, and is rotated at a constant speed.

The toner image adheres to the surface of the photosensitive drum 106 by the charging, exposing, and developing processes. This toner image moves to the recording paper in a transfer process, and is fused and fixed to the recording paper in a fixing process. Further, the photosensitive drum 10
The surface of No. 6 is initialized by the erase and cleaning processes, and the cycle of these processes is repeated.

With such a configuration, it is possible to realize a printer that has a long service life, high resolution, high speed, and simple control while maintaining compatibility with a conventional printer in processes, controls, main components, and the like. This is because the Se-based photosensitive drum 106 having the above-described high friction characteristics, high-speed response characteristics, and high sensitivity characteristics.
And a laser light source device 101 using a GaN-based semiconductor laser chip having short wavelength characteristics and high environmental characteristics.

FIG. 2 shows an example of the characteristics of the Se-based photosensitive drum 106 in the laser printer according to the present invention. The Se-based photosensitive drum 106 has a spectral sensitivity characteristic peak at a wavelength near 400 nm. Writing (exposure) with a laser beam of this wavelength makes it possible to create a high-speed response and high-resolution latent image. An advantageous feature of the laser light source device 101 using a GaN-based semiconductor laser chip is that the emission wavelength can be adjusted to an optimum value by adjusting the band gap. Specifically, while the band gap of GaN is 3.4 eV, InN (band gap =
By forming a mixed crystal with 2.0 eV) or AlN (6.3 eV), the band gap energy can be changed in a range from 2.0 eV to 6.3 eV. This means that the oscillation wavelength of the GaN-based semiconductor laser chip can be set arbitrarily within a wide range from ultraviolet to green, and a laser having a wavelength suitable for the peak sensitivity of the Se-based photosensitive drum 106. The band gap of the GaN-based semiconductor laser chip can be optimally designed so that the laser light source device 101 emits light.

As described above, by adopting a system in which the Se-based photosensitive drum 106 is employed and the laser light source device 101 using a GaN-based semiconductor laser chip is combined, the laser beam printer can be reduced in size, speed, and resolution. Will be possible.

FIG. 3 is a vertical sectional side view showing a first embodiment of a GaN semiconductor laser chip 300 of a laser light source device 101 using a GaN semiconductor laser chip in a laser printer according to the present invention.

As the substrate 313, a C-plane sapphire substrate is used. A GaN buffer layer 301, an n-GaN contact layer 302, an n-InGaN anti-crack layer 303, an n-AlGaN cladding layer 304, an n-GaN guide layer 305, an InGaN multiple quantum well (MQW) light emitting layer 306, p-AlGaN internal cladding layer 307, p-GaN guide layer 308, p-AlGaN cladding layer 30
9, a structure in which a p-GaN contact layer 310 is formed. Since the sapphire substrate 313 is an insulator, the n-electrode 312 is etched to the n-GaN contact layer 302 and formed on the upper surface of the contact layer 302. Also,
Since the C-plane sapphire substrate 313 has no cleavage, the cleavage plane used in a conventional GaAlAs-based semiconductor laser chip or the like cannot be used as a laser resonator plane. Therefore, in the GaN-based semiconductor laser chip 300 according to the present invention, the cavity surface was formed by dry-etching the epitaxial layer from above. A current injection electrode (p-electrode 311) is formed on the p-GaN contact layer 310, and a ground contact electrode (n-electrode 31) is formed on the n-GaN contact layer 302.
2) is formed.

According to the GaN-based semiconductor laser chip 300 having such a configuration, stable emission of the semiconductor laser can be obtained, and the wavelength can be shortened to 430 nm, so that higher-speed and higher-quality printing can be performed. .

FIGS. 4 and 5 are a plan view and a vertical sectional side view showing a second embodiment of the GaN semiconductor laser chip 400 in the laser light source device 101 according to the present invention.

This GaN-based semiconductor laser chip 400
First, an n-Al _0.2 Ga _0.8 N cladding layer 4 is formed on an n-SiC substrate 401.
02, a multiple quantum well active layer 403, a p-Al _0.2 Ga _0.8 N cladding layer 404, and a p-GaN contact layer 405 were sequentially grown. The multiple quantum well active layer 403 has seven layers of Al _0.1 G
a _0.7 In _0.2 N well layer (2 nm) and eight Al _0.3 Ga _0.7 N barrier layers
(2 nm).

A p-SiC layer 406 having a thickness of about 0.5 μm is provided on the surface of the n-SiC substrate 401 by implantation of boron, and a width of about 3 μm and a depth of about 409 μm are formed in a stripe region 409 serving as a semiconductor laser waveguide. A 1 μm groove 407 is formed. When a crystal is grown on a substrate having such a step, the active layer 40
Steps 3 are also formed, which becomes an optical waveguide structure. An optical waveguide structure using such a step is made of AlGaAs or AlGa.
Other materials, such as InP, cause reliability problems,
With a GaN-based crystal that can obtain sufficient reliability if the defect density is 107 or less per square cm, a semiconductor laser chip with sufficiently high reliability can be obtained with this structure.

An electrode 4 mainly composed of Au is provided on the surface of the wafer.
10 and then mechanically polished and chemically etched to form Si
The C substrate 401 was etched to a thickness of about 100 μm, and an electrode 411 containing Au as a main component was formed also on the SiC substrate 401 side.

The semiconductor wafer was cleaved into bars at intervals (width) of about 600 μm. The cleavage position error was about 1 μm.

According to the GaN-based semiconductor laser chip 400 having such a configuration, the semiconductor laser can emit light stably and also has the effect of shortening the wavelength to 430 nm, so that higher-speed and higher-quality printing can be performed. . Also, since the n-SiC substrate 401 is used, cleavage can be performed, and a resonator surface can be formed without using dry etching. Is simplified.

FIGS. 6 and 7 are a plan view and a vertical sectional side view showing a third embodiment of the GaN semiconductor laser chip 600 in the laser light source device 101 according to the present invention.

This GaN-based semiconductor laser chip 600
First, an n-Al _0.2 Ga _0.8 N cladding layer 4 is formed on an n-SiC substrate 401.
02, a multiple quantum well active layer 403, a p-Al _0.2 Ga _0.8 N cladding layer 404, and a p-GaN contact layer 405 were sequentially grown. The multiple quantum well active layer 403 has five layers of Ga _0.7 I
An n _0.3 N well layer 405 and six Al _0.5 Ga _0.5 In _0.5 N barrier layers 406 are alternately stacked. n-SiC substrate 4
On the surface of No. 01, a width of about 3 μm serving as a semiconductor laser waveguide was
A ridge 701 having a height of 1 μm is formed. Such a ridge 701 is not formed in a range of 5 μm serving as a laser end face. In a region outside the ridge, a p-SiC layer 406 having a conductivity type inverted to p-type by boron ion implantation is formed. Electrode 410 mainly composed of Au on the surface of the wafer
Is formed, and the SiC substrate 401 is etched to a thickness of about 100 μm by mechanical polishing and chemical etching.
An electrode 411 mainly containing Au was also formed on the 01 side. Such a semiconductor wafer was cleaved at an interval (width) of 600 μm to obtain a laser chip.

According to the GaN-based semiconductor laser chip 600 having such a structure, stable emission of the semiconductor laser can be obtained, and the wavelength can be shortened to 430 nm, so that higher-speed and higher-quality printing can be performed. . Further, since the n-SiC substrate 401 is used, cleavage can be performed, and a resonator surface can be formed without using dry etching. Therefore, manufacturing is simpler than the structure according to the first embodiment. Become.

The example of the structure of the GaN-based semiconductor chip has been described above. However, if the above-mentioned components are used as materials, the combination of materials and the manufacturing method are not limited.

FIG. 8 shows a laser light source device 10 according to the present invention.
1 is a perspective view showing a first embodiment of a package structure of a GaN-based semiconductor laser chip 300 in FIG.

The laser light source device 101 is configured to be connectable to a normal laser package by a comparator. Ga
The N-based semiconductor laser chip 300 is mounted on the C-plane sapphire substrate 3 in parallel with the column 807 of the semiconductor laser package 801.
13 is attached and installed. Similarly, a PD sensor 802 for detecting light emission power is mounted in the semiconductor laser package 801. Also, as external electrodes, the electrode pins 80
3, the PD monitor pin 804 and the ground pin 805 are set in an airtight state by glass welding. These electrode pins 803 to 805 are respectively connected to the current injection electrode 311 (p-GaN contact layer 310) in the GaN-based semiconductor laser chip 300 and the support 80 of the semiconductor laser package 801.
7. Wire-bonded to the monitor photodiode 802. Semiconductor laser package 801 and support 807
Is the ground common electrode.

Finally, the metal cap is hermetically sealed in a dry nitrogen gas by a ring weld, seam weld, or laser weld method.

At the outlet for emitting a laser beam, for example,
An anti-reflection code glass 806 sealed with low melting point glass is provided.

FIG. 9 shows a laser light source device 10 according to the present invention.
1 GaN-based semiconductor laser chip 400 (600)
1 is a perspective view showing a first embodiment of the package structure of FIG. The laser light source device 101 is also configured to be connectable with a normal laser package by a comparator.

The GaN-based semiconductor laser chip 400 (60
In (0), the electrode 411 on the bottom surface of the n-SiC substrate 401 is attached in parallel with the column 807 of the semiconductor laser package 801. Similarly, a PD sensor 802 for detecting light emission power is mounted in the semiconductor laser package 801. As external electrodes, electrode pins 803, PD monitor pins 804,
The ground pin 805 is set in an airtight state by glass welding. These electrodes 803 to 805 are respectively formed by a current injection electrode 410 (p-GaN contact layer 40) in the GaN semiconductor laser chip 400 (600).
5) Wire bonding to the support 807 of the semiconductor laser package 801 and the monitor photodiode 805. The semiconductor laser package 801 serves as a ground common electrode.

Finally, the metal cap is hermetically sealed in a dry nitrogen gas by a ring weld, seam weld, or laser weld method.

At the outlet for emitting a laser beam, for example,
An anti-reflection code glass 806 sealed with low melting point glass is provided.

FIG. 10 is a block diagram showing a first embodiment of the optical system controller 1000 in the laser printer according to the present invention. This circuit configuration is configured to use the laser light source device 101 shown in FIGS.

The laser drive current generator 1006 is connected to the electrode pin 803. The laser drive current feedback control unit 1010 is connected to the PD monitor pin 804.

The synchronizing signal / clock generation unit 1001
Controlled by the BD sensor signal 109 from the sensor 107,
Image synchronization clock 1003 and line synchronization signal 1004
Occurs. At this time, the reference basic clock 101
As 2, the output signal of the basic clock generator 1002 is used. The generated image synchronization clock 1003 and line synchronization signal 1004 are transmitted to the printer central control unit 2000.
And is used for the transfer timing of the image signal 108 between the optical system controller 1000 and the printer central controller 2000. At the same time, it is also used for the operation timing of the laser drive current generator 1006 in the optical system controller 1000.

The GaN semiconductor laser chip 300 (40
0,600) is driven by the laser drive current 1007. GaN-based semiconductor laser chip 300 (400, 60
The laser drive current 1007 to flow in 0) is generated by the laser drive current generator 1006. At the time of printing, first, in order to set the initial light intensity of the GaN-based semiconductor laser chip 300 (400, 600) from the printer central control unit 2000, the initial setting light intensity signal 1011 is transmitted to the initial drive current setting unit 1
009 is input. The initial drive current setting unit 1009
Initial setting current signal 1014 based on the input setting value
Is supplied to the laser drive current generator 1006. afterwards,
In order to absorb variations in characteristics between lasers, the initial light amount is adjusted by feedback control described later.

In parallel with the adjustment of the initial light amount, the laser drive current generation unit 1006 performs the above-mentioned GaN-based semiconductor laser chip 300 (400, 600) in order to guarantee the characteristics due to temperature change. Chip 3
APC (Auto Power Control) by the laser drive current feedback control unit 1010 that watches the output light amount (light emission amount monitor signal 1008) from 00 (400, 600).
l) Control is performed. At this time, the laser drive current feedback control unit 1010 outputs the feedback control signal 101
3 is generated, and the laser drive current generation unit 1006 controls the light amount together with the light emission intermittent control required for the image signal 108.

In a normal control circuit, it is necessary to severely guarantee characteristics due to a temperature change, so that feedback control is often required for each line. However, the GaN semiconductor laser chip 300 (400, 60) used in the laser light source device 101 of the laser printer according to the present invention.
If the environmental characteristics are stable as in 0), severe feedback control is not required, and there is no need to have a fine timing switching circuit for each scan, which leads to a reduction in circuit scale and cost reduction. Becomes possible.

In the case of a GaN semiconductor laser, 1
It is more advantageous to increase the exposure intensity and perform pulse emission at a duty of about 10% a plurality of times within one pixel emission time by using a method of continuously emitting light during the pixel emission time. This is effective for ensuring the life of the laser chip and the stability of light intensity.
This is a characteristic of the GaN-based semiconductor laser chip 300 (400, 600). For this purpose, the laser drive current generator 100
6 preferably has both a drive capability in the CW mode and a CCW mode for pixel emission.

FIG. 11 is a perspective view showing a second embodiment of the scanning optical system 100 in the laser printer according to the present invention. This embodiment employs a multi-exposure method to cope with a further increase in speed.

Although the basic configuration is the same as that of the above-described embodiment, a laser light source device 110 having a GaN-based semiconductor laser chip array forming three light emitting portions as a light source is built in.
1 is used. The current printing speed limiting factor of the laser printer is the mechanical rotation speed of the polygon mirror 104. In this embodiment, this is compensated for by multiple exposure. Accordingly, the package configuration of the GaN-based semiconductor laser chip and the configuration of the optical system control unit 1102 in the laser light source device 1101 have changed.

FIG. 12 is a perspective view showing a first embodiment of a package structure of a laser light source device 1101 using a GaN-based semiconductor laser chip array in a laser printer according to the present invention. Packaging methods, etc.
This is the same as the packaging shown in FIGS. This embodiment has a package configuration using an array of the GaN-based semiconductor laser chips 400 (600) described as the second and third embodiments in the laser light source device 101 described above.

In this embodiment, three GaN-based semiconductor laser chips are arrayed (GaN-based semiconductor laser chip array 1300). The GaN-based semiconductor laser chip array 1300 forms three light emitting units (light emitting unit-1 1302, light emitting unit-2 1303, light emitting unit-3 1304). The light emission of each of the light emitting units 1302 to 1304 is controlled by current injection from the corresponding electrode pin (electrode pin-1 1313, electrode pin-2 1314, electrode pin-3 1315).

The semiconductor laser package 801 of this embodiment is different from a normal laser package in that the number of electrode pins is equal to the number of chips in the cathode portion (electrode pin-1 131).
3, electrode pin-2 1314, electrode pin-3 1315). The PD sensor 802 includes light emitting units 1302-1
The configuration is used in common with 304. This positively utilizes the fact that the GaN-based semiconductor laser chip array 1300 is excellent in environmental friendliness. If the amount of light is set serially for each laser chip when the power of the printer is turned on, the light can be used during normal printing with a light amount variation that does not cause any problem. If more accurate light amount setting is required, a method of performing the above-described sequence between print pages or a method of switching a laser for controlling light amount for each print line may be employed.

Each light emitting section (semiconductor laser chip) 1302
In order to monitor the light emission amounts of the light sources 1 to 1304 in real time, the laser light source device 110 shown in FIG.
1, each light emitting unit 1302-1
The light emission wavelength of the light emitting unit 304 is slightly different (light emitting unit-1 130
1: emission wavelength λ1, emission section-2 1302: emission wavelength λ2,
Light emitting unit-3 1303: three light emitting diodes (PD sensor-1 1307, PD sensor-2 1308, PD sensor-3 1309) manufactured and arranged with light emitting wavelengths λ3) and corresponding to the respective light emitting units 1302-1304. Provided in parallel, each PD sensor 1307
To 1309 for three colors (band-pass filter-1 1304: filter wavelength λ1,
Bandpass filter-2 1305: filter wavelength λ2, bandpass filter-3 1306: filter wavelength λ3). With such a configuration, each light emitting unit 1
302 to 1304 emit light simultaneously, and each PD sensor 130
Individual light amount feedback control by 7-1309 can be performed. This configuration is also effective when the laser chip array is used as a light source of three primary colors. However, the package pins (electrode pin-1 1313, electrode pin-2 131
4, electrode pin-3 1315, PD monitor pin-1 1310,
PD monitor pin-2 1311, PD monitor pin-31312)
There are disadvantages in that the number of components increases, the configuration and implementation become complicated, and the circuit scale increases.

Next, as shown in FIG. 8, when the GaN-based semiconductor laser chip 300 described in the first embodiment is used as the GaN-based semiconductor laser chip, the sapphire substrate 313 is used. Is attached to the column 807 on the bottom surface of the column. Therefore, from the n-electrode 312 to the support 8
07 needs to be ground-bonded.
As for heat dissipation, there is no practical problem in heat dissipation to the sapphire substrate 313 and the atmosphere.

However, as shown in FIG. 9, the GaN-based semiconductor laser chip 4 described in the second or third embodiment
00 (600), the contact layer 40
Since the electrode 411 on the bottom surface of the first electrode 411 is attached to the column 807, grounding is realized by the attachment. Regarding heat dissipation, there is no practical problem in heat dissipation to the n-SiC substrate 401 and the atmosphere.

The optical system control unit 1102 inputs image signals 1402, 1405, and 1407 for three lines in parallel.
A laser drive current for driving the three light emitting units 1301 to 1303 of the GaN-based semiconductor laser chip array 1300 in parallel is generated in parallel.

FIG. 14 is a block diagram showing a first embodiment of the optical system controller 1102 in the laser printer according to the present invention. This circuit configuration is basically a configuration in which three sets of the configuration of the optical system control unit 1000 shown in FIG. 10 are provided so as to correspond to three light emitting units. As shown in FIG. GaN-based semiconductor laser chip array 1300 including 1301 to 1303 and three PD sensors 13
Laser light source device 1 packaged with 07 to 1309
101.

The three laser drive current generators (laser drive current generator-1 1409, laser drive current generator-214)
12, the laser drive current generating section-3 1415) respectively has an electrode pin (electrode pin-1 1313, electrode pin-2 1313).
14, electrode pin-3 1315). The laser drive current feedback control units (laser drive current feedback control unit-1 1410, laser drive current feedback control unit 21413, and laser drive current feedback control unit 31416) are respectively provided with PD monitor pins (PD monitor pin-1 1310). , PD monitor pin-2 131
1, PD monitor pin-3 1312).

The synchronization signal / clock generation unit 1001
The image synchronization clock 1003 and the line synchronization signal 1004 controlled by the BD sensor signal 109 from the D sensor 107
Occurs. At this time, the reference basic clock 101
As 2, the output signal of the basic clock generator 1002 is used. The generated image synchronization clock 1003 and line synchronization signal 1004 are sent to the printer central control unit 1403, and image signals (image signal-1 1402, image signal-2) between the optical system control unit 1102 and the printer central control unit 1403 are sent. 1405, image signal-3 1407). In addition, the optical system control unit 1102
Of the three laser drive current generators (laser drive current generator-1 1409, laser drive current generator-2 1412, laser drive current generator-3 1415).

GaN-based semiconductor laser chip array 1300
Of the laser driving currents (laser driving current-1 1418, laser driving current-
2 1422, and a laser drive current 31426). These laser drive currents 1418 to 1426
Are laser drive current generators (laser drive current generator-1 1409, laser drive current generator-2 141), respectively.
2, generated by the laser drive current generation unit-31415).

At the time of printing, first, the GaN semiconductor laser array chip 130 is sent from the printer central control unit 1403.
In order to set the initial light intensity of each of the light emitting units 1301 to 1303 of 0, an initial light intensity signal (initial light intensity signal-114)
01, the initial setting light quantity signal-2 1404, the initial setting light quantity signal-3 1406) are the initial driving current setting sections (the initial driving current setting section-1 1408, the initial driving current setting section-2 411, the initial driving current setting section-3). 1414). Each of the initial drive current setting units 1408, 1411, and 1414) performs an initial setting current signal (initial setting current signal-1 1417, initial setting current signal-2 1421, and initial setting current signal-3 1425) based on the input value. Is generated for each of the laser drive current generators 1409, 1412, and 1415. After that, in order to absorb variations in characteristics between laser chips, the initial light amount is adjusted by feedback control described later.

Each laser drive current generator 1409, 141
Reference numerals 2 and 1415 denote light from each of the light emitting units 1301 to 1303 of the GaN-based semiconductor laser array chip 1300 in order to guarantee the characteristics of the GaN-based semiconductor laser chip array 1300 due to temperature change, in addition to the adjustment of the initial light amount described above. The output light amount is measured by the light emission amount monitor signal-1 1419, light emission amount monitor signal-2 1423, light emission amount monitor signal-3 1427
In each of the laser drive current feedback controllers 1410, 1413, and 1416.
(Auto Power Control) Control is performed in parallel. At this time,
Each laser drive current feedback control unit 1410, 14
13, 1416 are feedback control signals (feedback control signal-1 1420, feedback control signal-
2 1424, a feedback control signal-3 1428), and the laser drive current generators 1409, 1412,
Reference numeral 1415 denotes each image signal 1402, 1405, 1407
The light amount is controlled together with the light emission intermittent control necessary for

In a normal control circuit, since it is necessary to severely guarantee characteristics due to a temperature change, feedback control is often required for each line. However, when the GaN-based semiconductor laser array chip 1300 used in the laser light source device 1101 of the laser printer according to the present invention has stable environmental characteristics, severe feedback control is not necessary, and fine control within one scan is not required. There is no need to have a timing switching circuit, etc.
This can lead to lower prices.

For use in a single color, not only can the circuit scale be reduced, but also each of the light emitting units 1401 to 1
The emission wavelength λ of 403 can be set to λ1 = λ2 = λ3, and a configuration in which a bandpass filter is not required can be adopted. With such a configuration, it is possible to manufacture the laser chip array and assemble the packaging in a simple process, which leads to a reduction in cost.

Here, the specific configuration of the laser chip array is as follows. Since GaN has good thermal conductivity, it is necessary to take measures to avoid thermal crosstalk between adjacent light emitting portions. For this purpose, an interval of about 5 times the width of the light emitting section is required between each light emitting section, and since this image is enlarged and formed on the photosensitive drum, the line interval is longer than the required line interval. There is a problem that opens. In order to solve this problem, the lines of the laser light emitting portions are usually aligned in the vertical direction, but by rotating them around the axis of the light emitting direction and shifting them, the effective line spacing is reduced. It is desirable to use a narrowing technique. In the case of a GaN-based semiconductor laser chip, it is inevitable that the laser drive voltage increases from the viewpoint of material and structure, and this method is effective for realizing high resolution.

FIG. 15 is a block diagram showing a second embodiment of the optical system control unit 1102 that positively utilizes the characteristics of the GaN semiconductor laser chip described above.

This embodiment is different from the embodiment shown in FIG. 14 in that the initial drive current setting sections 1408, 1411, and 14 are provided.
14, a laser drive current feedback control unit 1410,
1413 and 1416, the initial drive current setting unit 1501,
This configuration is integrated with the laser drive current feedback control unit 1502. By utilizing the fact that real-time and parallel use is unnecessary, the initial drive current setting unit 1501 and the laser drive current feedback control unit 1502 are time-shared (select use) by the respective laser drive current generation units 1409, 1412, and 1415. To use. Initial setting current signal 1503 and feedback control signal 1504 which are output signals from initial driving current setting section 1501 and laser driving current feedback control section 1502.
Is that the initial drive current setting unit 1501 and the laser drive current feedback control unit 1502 have output buffers corresponding to the three outputs, so that the output value changes only during use, and the output value is normally held (latched). To be.

By adopting such a configuration utilizing the environmental stability of the GaN-based semiconductor laser chip, the circuit scale can be reduced and the cost can be reduced.

In the embodiment shown in FIG. 15, the light emission amount monitor signal-2 1423 and the light emission amount monitor signal-3 1427 are omitted so that the optical system corresponding to the laser light source device 1101 shown in FIG. The control unit 1102 can be used. In this embodiment, the laser drive current generators 1409, 1412, and 1415 are connected to the electrode pins 1313 to 1315, respectively, and the laser drive current feedback controller 1502 is connected to the PD monitor pin 804.

The synchronization signal / clock generation unit 1001
The image synchronization clock 1003 and the line synchronization signal 1004 controlled by the BD sensor signal 109 from the D sensor 107
Occurs. At this time, the reference basic clock 101
As 2, the output of the basic clock generator 1002 is used. The generated image synchronization clock 1003 and line synchronization signal 1004 are sent to the printer central control unit 1403, and are used for the transfer timing of the image signals 1402, 1405, and 1407 between the optical system control unit 1102 and the printer central control unit 1403. In addition, the laser drive current generators 1409, 1412, and 1415 in the optical system controller 1102
Also used for the operation timing of.

GaN-based semiconductor laser chip array 1300
Of the laser drive current 14
18, 1422, and 1426. The laser drive currents 1418, 1422, and 1426 are generated by laser drive current generators 1409, 1412, and 1415.

At the time of printing, first, the printer central control unit 1403 sends the GaN semiconductor laser array chip 130
In order to set the initial light amount of each of the light emitting units 1301 to 1303 of 0, initial setting light amount signals 1401, 1404, 140
6 is input to the initial drive current setting unit 1501. The initial drive current setting section 1501 outputs an initial set current signal 1503 based on the input value to each laser drive current generation section 1401.
9, 1412, and 1415. After that, in order to absorb variations in characteristics between laser chips, the initial light amount is adjusted by feedback control described later.

Each laser drive current generator 1409, 141
Reference numerals 2 and 1415 denote each of the light emitting units 1301 to 1303 of the GaN-based semiconductor laser chip array 1300 in order to guarantee the characteristics of the GaN-based semiconductor laser chip array 1300 due to temperature change, in addition to the adjustment of the initial light amount described above. The output light amount is watched by the light emission amount monitor signal 1417, and the laser drive current feedback control unit 1502 performs APC (AutoPower Control) control in parallel. At this time, the laser drive current feedback control unit 1
502 generates a feedback control signal 1504;
Each laser drive current generator 1409, 1412, 1415
Controls the light amount together with the light emission intermittent control required for the image signals 1402, 1405, and 1407.

This is a configuration made possible by the environmental stability of the GaN-based semiconductor laser chip array 1300.
In addition to reducing the circuit scale, the light emitting units 1401 to 14
03 can be set to λ1 = λ2 = λ3, and a laser chip array can be manufactured by a simple process, which leads to cost reduction.

In the above-described laser printer, an embodiment using a drum as a photosensitive member has been described. However, the present invention can be similarly implemented by using a photosensitive member formed in a belt shape.

In each of the above embodiments, an example of a laser printer that performs parallel exposure using a laser light source device having a built-in laser chip array has been described. As another application example of such a laser light source device, an application as a light source of three primary colors (scanner light source, one-shot color printer, white, color light source, etc.) can be considered. In this case, three or more emission wavelengths are required. Also at this time, by adopting a configuration combining FIG. 12 and FIG. 15 based on a GaN-based semiconductor laser chip array or a multi-chip mounting, it becomes an effective method in terms of manufacturing, mounting, and cost.

[0093]

According to the present invention, there is provided an electrophotographic laser printer for forming a latent image on a photoreceptor by exposing a laser beam emitted from a laser light source device through an optical system. Using a laser chip having a laminated structure in which the laminated portion of the gallium nitride based semiconductor emits light at a wavelength of 550 nm or less, and the photoreceptor has a high sensitivity at a wavelength of 550 nm or less, thereby achieving high speed and high image quality. Achieve stable printing. In addition, a laser light source device using a gallium nitride based semiconductor laser chip can be reduced in size itself, and the short-wavelength laser beam emitted from the laser light source device can be used to reduce the size of a deflection scanning optical system. It is valid.

Further, the laser light source device of the present invention comprises a plurality of laser chips having a laminated structure in which a laminated portion of a gallium nitride based semiconductor emits light at a wavelength of 550 nm or less, and one light emitting element common to the plurality of laser chips. By incorporating the quantity detecting element in one package, a control circuit for stably emitting a laser beam from a plurality of light emitting units is simplified. By arranging separate light emission amount detection elements on a plurality of laser chips, the light emission amount of each laser chip can be detected in parallel in real time.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a first embodiment of a scanning optical system in a laser printer according to the present invention.

FIG. 2 is a sensitivity characteristic diagram of a Se-based photosensitive drum in the laser printer according to the present invention.

FIG. 3 is a vertical sectional side view showing a first embodiment of a GaN-based semiconductor laser chip of the laser light source device in the laser printer according to the present invention.

FIG. 4 is a plan view showing a second embodiment of the GaN-based semiconductor laser chip in the laser light source device according to the present invention.

FIG. 5 is a vertical sectional side view showing a second embodiment of the GaN-based semiconductor laser chip in the laser light source device according to the present invention.

FIG. 6 is a plan view showing a third embodiment of the GaN-based semiconductor laser chip in the laser light source device according to the present invention.

FIG. 7 is a vertical sectional side view showing a third embodiment of the GaN-based semiconductor laser chip in the laser light source device according to the present invention.

FIG. 8 is a perspective view showing a first embodiment of the packaging of the GaN-based semiconductor laser chip shown in FIG. 3;

9 is a perspective view showing a first embodiment of the packaging of the GaN-based semiconductor laser chip shown in FIGS. 4 to 7; FIG.

FIG. 10 is a block diagram illustrating a first embodiment of an optical system control unit in the laser printer according to the present invention.

FIG. 11 is a perspective view showing a second embodiment of the scanning optical system in the laser printer according to the present invention.

FIG. 12 is a perspective view showing a first embodiment of packaging of a GaN-based semiconductor laser chip in the laser light source device of the laser printer shown in FIG. 11;

13 is a perspective view showing a second embodiment of the packaging of the GaN-based semiconductor laser chip in the laser light source device of the laser printer shown in FIG. 11;

FIG. 14 is a block diagram showing a first embodiment of an optical system control unit in the laser printer shown in FIG.

FIG. 15 is a block diagram showing a second embodiment of the optical system control unit in the laser printer shown in FIG.

[Explanation of symbols]

Reference Signs List 100 scanning optical system 101 GaN semiconductor laser light source device 102 collimating lens 103 cylindrical lens 104 polygon mirror 105 fθ lens 106 Se photosensitive drum 107 beam detector (BD) sensor .., 108... Image signal, 109.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI H04N 1/113 H04N 1/04 104A

Claims (13)

[Claims] 1. A laser printer comprising: a laser light source device; and a photoconductor on which a latent image is formed by exposing a laser beam emitted from the laser light source device via an optical system. A laser chip having a laminated structure in which a laminated portion of a gallium nitride based semiconductor emits light at a wavelength of 550 nm or less, and wherein the photoreceptor has high sensitivity at a wavelength of 550 nm or less. 2. The light-emitting layer according to claim 1, wherein the light-emitting layer in the laminated portion of the gallium nitride-based semiconductor comprises an n-GaN guide layer and a p-Al _0.2 Ga
InGaN multiple quantum well structure sandwiched between _0.8 N clad layers (MQ
W) a laser printer. 3. The light-emitting layer according to claim 1, wherein the light-emitting layer in the laminated portion of the gallium nitride-based compound semiconductor is Ga _0.7 In sandwiched between an n-Al _0.2 Ga _0.8 N clad layer and a p-Al _0.2 Ga _0.8 N clad layer.
A laser printer having a multiple quantum well structure formed by alternately stacking _0.3 N well layers and Al _0.5 Ga _0.5 In _0.5 N barrier layers. 4. A laser printer according to claim 1, wherein said photosensitive member is a selenium-based photosensitive member. 5. A laser light source device which is turned on and off according to print information, and a laser beam emitted from the laser light source device is condensed and irradiated on the photoreceptor while deflecting the laser beam by a rotary polygon mirror. A laser printer having an optical system for forming a latent image, wherein the laser light source device includes a laser chip having a laminated structure in which a laminated portion of a gallium nitride based semiconductor emits light at a wavelength of 550 nm or less. A laser printer, wherein a laser beam is made substantially parallel to be reflected by a rotary polygon mirror and deflected, and the photoreceptor has high sensitivity at a wavelength of 550 nm or less. 6. The photoconductor according to claim 5, wherein the photoconductor has a thickness of 550 nm.
A selenium-based laser printer having high sensitivity to the following wavelengths: 7. A laser printer comprising: a laser light source device; and a photoconductor on which a latent image is formed by exposing a laser beam emitted from the laser light source device via an optical system. A plurality of laser chips having a stacked structure in which a stacked portion of a gallium nitride-based semiconductor emits light at a wavelength of 550 nm or less is provided in a state where a plurality of laser chips are juxtaposed, and the optical system emits a laser beam emitted from the plurality of laser chips. A laser printer, wherein the laser is configured to irradiate the photosensitive member in a collective manner, wherein the photosensitive member has high sensitivity at a wavelength of 550 nm or less. 8. The laser light source device according to claim 7, wherein a plurality of laser chips arranged side by side and one light emission amount detection element common to the plurality of laser chips are incorporated in one package. Laser printer. 9. The laser light source device according to claim 7, wherein the laser light source device includes a plurality of laser chips arranged side by side and a plurality of light emitting amount detecting elements provided for each of the plurality of laser chips in a single package. Laser printer characterized by the above-mentioned. 10. The laser light source device according to claim 7, wherein the laser light source device comprises: a plurality of laser chips having different emission wavelengths;
A laser printer, comprising: a plurality of band-pass filters interposed between the respective laser chips and the respective light-emission-amount detecting elements to transmit light emitted from the corresponding laser chips. 11. A gallium nitride-based semiconductor laminated portion having a thickness of 550 nm
A laser light source device comprising: a plurality of laser chips having a laminated structure emitting light at the following wavelengths; and a single light emission amount detection element common to the plurality of laser chips, incorporated in one package. 12. A gallium nitride-based semiconductor laminated portion having a thickness of 550 nm.
A laser light source device comprising: a plurality of laser chips having a laminated structure emitting light at the following wavelengths; and a plurality of light emission amount detecting elements provided for each of the plurality of laser chips, in a single package. 13. The control according to claim 11, wherein the laser chip and the light emitting amount detecting element detect the light emitting amount of each laser chip by the light emitting amount detecting element and feedback-control the light emitting amount of the laser chip in a time division manner. A laser light source device connected to a circuit.