JP5047713B2 - Latent image measurement device for micro area of photoconductor - Google Patents

Description

  The present invention relates to a minute area latent image measuring device on an electrophotographic photoreceptor utilizing light attenuation.

  An electrophotographic method used in a copying machine or a laser printer is formed by a process of uniformly charging the surface of a photoconductor and a process of exposing the charged photoconductor surface to form an electrostatic latent image on the surface of the photoconductor. Developing the electrostatic latent image with toner in the developer, transferring the toner image to paper or an intermediate transfer belt, fixing the transferred toner image, and on the photoreceptor after transfer It consists of a cleaning process for removing residual toner and a charge eliminating process for removing the electrostatic latent image on the photoreceptor.

  Since each process has an effect on the output quality of the final image, it is not easy to know the latent image quality in the exposure process from the final image. Estimate the quality of the latent image formed by measuring the post-potential and seeing how these characteristic values change in a temperature and humidity environment or after repeated charging and exposure cycles. I had to do it. However, in this method, evaluation of abnormal images such as background contamination, image blur (or image blur), which is degradation of the latent image, which is a deterioration of the latent image, is based on the fact that the surface electrometer measures a wide area on the photoconductor (photoconductor surface). Since the charging potential in the region of 10 to 15 mmφ with respect to the distance of 2 mm between the surface electrometer probe and the surface electrometer probe was measured macroscopically, it was impossible to know the abnormality of the latent image.

In the trend toward higher image quality, there is a need for a method of directly measuring an electrostatic latent image in a minute area and evaluating the state of the latent image. For this reason, several methods for directly evaluating an electrostatic latent image in a minute area have been proposed recently.
For example, (1) Cantilever method: mechanical displacement of a cantilever beam caused by a force F (electrostatic attractive force, etc.) acting between the photoreceptor surface and the probe, or a change in vibration state is applied to the back surface of the cantilever beam. A method of irradiating a laser beam, detecting the reflected light, and knowing the surface potential from the value of the amount of displacement (see Patent Document 1: Japanese Patent Laid-Open No. 5-119093, Patent Document 2: Japanese Patent Laid-Open No. 5-149988) ), (2) Electrometer method: a method in which an electrode having a certain area is disposed in the vicinity of the surface of the photosensitive member, and the electric potential induced in the electrode has a potential with respect to the ground (Patent Document 3: Japanese Patent Laid-Open 11-184188, Patent Document 4: JP-A-11-184189, Non-Patent Document 1: W. Hillen et al, SPIE Vol. 914 Medical Imaging II (1988) p253, Non-Patent Document 2: Enrique Garcia et al. , IEEE Transaction Devices 38 (5) (1991) p1077), (3) Displacement current method by light attenuation (inductive current method): An electrode placed close to the surface of the photoconductor, irradiating a charged surface of the photoconductor with a very small light spot, Method of measuring the amount of electric charge (induced current) induced in the electrode and knowing the surface potential (Non-patent Document 3: Takeshima Motoharu et al., Japan Hardcopy 2001 Proceedings, B-32, 281 pages, Non-Patent Document 4: JARowlands et al, Med. Phys. 18 (3), May / Jun 1991, p421).

  In the method (1), the cantilever and the photosensitive member come into contact with each other with an electrostatic force at a charging potential of several hundred volts as in the photosensitive member. Further, if the distance is set so as not to contact, the spatial resolution is lowered, and there is a problem that sensitivity deterioration cannot be avoided if a material having a bending force that does not contact the distance as it is is used for the cantilever beam.

In the method (2), it is necessary to induce an amount of charge corresponding to the amount of charge in a predetermined region on the surface of the photoreceptor on the electrode, and it is necessary to narrow the gap between the photoreceptor and the electrode. In general, in this method, when A (μm) is required as the spatial resolution of measurement, the gap must be within A (μm), and the electrode size must be within A (μm) × A (μm). (See Non-Patent Document 2). Therefore, in order to realize a spatial resolution of 10 μm, it is necessary to make a gap of 10 μm or less with a small electrode of 10 × 10 μm ² or less. In this method, since the charged photoconductor moves and the displacement current induced when the charge on the surface of the photoconductor crosses the electrode is measured, it is necessary to always maintain this minimum gap. Is extremely difficult. In Patent Document 3 and Patent Document 4 adopting this method, there is a description that means for keeping the distance between the surface of the photoreceptor and the detection portion of the potential sensor constant is provided. To provide a mechanism to maintain a constant interval mechanically, or to monitor the interval using a laser gap sensor or an eddy current displacement sensor and control with a motor or the like to always maintain a constant interval Are listed. However, if the spacer is sandwiched between the surface of the photoconductor surface and the electrode, it is obvious that the surface is scratched with the movement of the photoconductor surface, which is not preferable. In addition, the eddy current method for monitoring distance has a problem of responsiveness of distance measurement, and the laser method absorbs light by the photoconductor and the reflected light becomes small and an error is likely to occur. It can be said that it is not preferable to use the photoconductor as a counterpart because it causes unnecessary photodegradation. In Non-Patent Document 1, 32 microelectrometers (electrodes) each having a size of 0.2 × 0.2 mm ² are arranged in the drum axis direction at a pitch of 12 mm, and the average gap with the photoconductor is 0.1 mm ± 0. .02mm is realized. The error is assumed to be due to the placement error of each electrode and the rotational deviation of the photosensitive drum, and there is no description of a specific mechanism for maintaining the gap with high accuracy. Non-Patent Document 2 uses a CCD array (5 × 5 μm 2) as an electrode, but it is described that a target of a gap of 5 μm can be controlled and maintained only to about 20 μm using a pneumatic bearing. . Details about the mechanism are unknown. In any case, the electrode must be made small for spatial resolution, the signal obtained is small because it is small, and a mechanism for maintaining a minimum gap on the order of μm is prepared. Measurement is difficult and measurement is not easy.

  In the method (3), an electrode in which a transparent conductive film is formed on transparent glass is used, and light irradiation is performed from the back side. In principle, the spatial resolution depends only on the size of the spot light to be irradiated. The electrode size is arbitrary. The distance (gap) between the surface of the photoconductor and the probe is also arbitrary up to about 2 mm (however, as a matter of course, the detection signal decreases as the gap increases). By the way, according to Non-Patent Document 3, a 10 μm-sized beam spot is irradiated from the back surface of the transparent glass electrode, an induced current (displacement current) due to a change in optical attenuation potential generated in the 10 μm region is detected, and the magnitude of the signal From this, the potential before spot light irradiation is known, and the measurement position is sequentially changed to obtain a latent image profile (one-dimensional profile in the sub-scanning direction), but one line of latent image is obtained with a beam of 80 μm width (sub-scanning direction). The latent image width at the time of writing is measured to be a width (μm) which is about twice as large as 80 μm width, and this is a method that is technically excellent, but this method is also a method for which further improvement is desired.

  Non-Patent Document 4 also relates to the method of (3), and mentions the principle of measurement using the light attenuation characteristics of the photosensitive member. However, the X-ray fluoroscopic image of the human body is not a silver halide film. Instead, it describes the technical problem of the image output apparatus when it is projected onto a charged inorganic photoreceptor (Se) and directly printed on plain paper.

In addition to this, there are those related to measuring a latent image of a minute region using an electron beam (Patent Documents 5 to 8).
Patent Document 5: Japanese Patent Laid-Open No. 2006-84434 describes that the insulation resistance is evaluated with an accuracy of the order of μm, and Patent Document 6: Japanese Patent Laid-Open No. 2006-10430 includes a detection means. Patent Document 7: Japanese Patent Application Laid-Open No. 2005-166542 discloses that surface potential distribution is measured with extremely high accuracy without using secondary electrons. Patent Document 8: Japanese Patent Application Laid-Open No. 2004-251800 describes a method for accurately measuring the surface charge distribution by setting the irradiation current of the charged particle beam to a size that does not cause the surface charge distribution to disappear. ing.
However, when the sample is measured in a vacuum, and it is desired to evaluate the electrostatic latent image created on the deteriorated sample, the surface has something to be attached by taking time and taking the vacuum. If so, it is possible that it will be removed and the degradation state will change. Therefore, the present invention differs from the present invention in configuration, technical problem, and purpose. Patent Document 9 is a publication of an already-invented invention related to the present inventor, and the present invention corresponds to the improved application invention of Patent Document 9.
Patent Document 9: Japanese Patent Laid-Open No. 2006-38666 describes that in the measurement of displacement current due to a change in optical attenuation potential, the S / N ratio of the detection signal is improved while ensuring the spatial resolution in the sub-scanning direction. .

Japanese Patent Application Laid-Open No. 5-119093 Japanese Patent Laid-Open No. 5-149988 JP-A-11-184188 JP-A-11-184189 JP 2006-84434 A JP 2006-10430 A JP 2005-166542 A JP 2004-251800 A JP 2006-38666 A W. Hillen `` A selenium-based detector system for digital slot-radiograph '' SPIE Vol.914 Medical ImagingII, P253,1988 Enrique Garcia “CCD Arrays for Readout of Electrophotographic Latent Images” IEEE TRANSACTIONS ON ELECTRON DEVICES 38, NO.5, P1077, 1991 Takeshima, Aizawa "1DOT Latent Image Potential" Japan Hardcopy 2001 Proceedings p281 J. A Rowlands et al. `` X-ray imaging using amorphous selenium: A photoinduded discharge readout method for digital mammography '' Med.phys 18 (3), 1991

The present invention belongs to (3) of the prior art, and relates to the application of this method. By measuring in the atmosphere, the photoconductor without deteriorating the initial state of the photoconductor and the deterioration state due to the load. It is intended to provide a latent image measuring device that directly evaluates the electrostatic latent image on the top and knows the resistance of the photoreceptor to the load, and a latent image pattern forming method for evaluation suitable for this purpose. .
[Purpose 1]
Around the cylindrical photoconductor, there are a charger, an exposure device (1) (latent image writing means), a transparent conductive electrode, an exposure device (2) (detection light exposure means) on the back side, and a static eliminator in this order. The latent image pattern is formed on the surface of the photosensitive member by the exposure device (1), and when the pattern reaches the transparent conductive electrode portion, the rotational movement of the photosensitive member is stopped, and the exposure device (2) One-shot pulse exposure is performed, a signal induced in the transparent conductive electrode is collected as the charge on the photosensitive member is attenuated, and then the photosensitive member is exposed to a beam width (hereinafter referred to as “thickness”) in the circumferential direction of the exposure device (2). In the measuring apparatus that moves in steps as described above and repeats signal sampling in the same manner, the latent image pattern formed by the exposure device (1) has at least 2 lines / mm or more in the rotation direction of the photosensitive member. By controlling the exposure device (1) to be a pattern and forming a latent image, The resolution characteristics of the optical body load and accompanied to the photoreceptor, providing a small area latent image measuring apparatus capable of easily evaluating how changes.
[Purpose 2]
By controlling the exposure unit (1) so that the line pattern of the latent image formed by the exposure unit (1) is a potential pattern attenuated in a substantially V-shape to form a latent image, Provided is a minute region latent image measuring device capable of easily evaluating resolution characteristics of a body.
[Purpose 3]
3. The latent image pattern according to claim 2, wherein the exposure device (1) is controlled so that the width of the one side inclined portion of one V-shaped potential pattern is at least twice the distance of one step movement. Provided is a minute area latent image measuring device capable of easily evaluating the resolution characteristics of a photoreceptor by forming an image.
[Purpose 4]
4. The latent image pattern according to claim 3, wherein the potential of an unexposed portion sandwiched between two V-shaped potential patterns is at least twice the distance of one step movement, and the maximum potential and the minimum in this range. Provided is a microregion latent image measuring apparatus that can easily evaluate the resolution characteristics of a photosensitive member by controlling the exposure device (1) so that the potential difference is within 100 V and forming a latent image.
[Purpose 5]
By using an exposure device (1) according to claims 1 to 4 as a line beam laser, a minute area latent image measuring device capable of easily forming a latent image pattern for resolution evaluation is provided.
[Purpose 6]
The exposure device (2) according to claims 1 to 5 is a line beam, and the line beam length is a line beam laser shorter than the line beam length of the exposure device (1), so that an accurate potential measurement can be performed. Providing a small area latent image measuring device.
[Purpose 7]
7. The light power output of the line beam laser of the exposure device (1) according to any one of claims 1 to 6 is less than that energy, preferably 1/2 or less of the "required exposure energy" of the target photoreceptor. A micro-region latent image measuring device for the purpose of facilitating the creation of a latent image pattern whose resolution is easy to evaluate by being controlled to reach.

The above-mentioned subject is achieved by the present invention as follows.
(1) “A charger, an exposure device (1) (latent image writing means), a transparent conductive electrode, and an exposure device (2) disposed on the back side of the cylindrical photoconductor (detection light exposure means) ), The static eliminator is arranged in this order, and the exposure device (1) forms a latent image pattern on the surface of the photosensitive member, and when the pattern reaches the transparent conductive electrode portion, the rotational movement of the photosensitive member is stopped. The exposure device (2) performs one-shot pulse exposure, collects a signal induced in the transparent conductive electrode as the charge of the photoconductor is attenuated, and then removes the photoconductor in the circumferential direction of the exposure device (2). In a measuring apparatus that moves in steps beyond the beam width (hereinafter referred to as thickness) and repeats signal sampling in the same manner, the latent image pattern formed by the exposure device (1) is at least 2 in the photoconductor rotation direction. and controls the exposure device (1) such that the above line pattern present / mm, each The thickness direction of the potential shape of the line in-in pattern, micro-region latent image measuring device, characterized in that measured including the potential of the unexposed portion sandwiched the line. ";
(2) “The exposure unit (1) is controlled such that the line pattern of the latent image formed by the exposure unit (1) is a potential pattern attenuated in a substantially V shape ( The microregion latent image measuring device according to item 1). ”;
(3) “In the latent image pattern, the exposure device (1) is controlled so that the width of the one-side inclined portion of one V-shaped potential pattern is at least twice the distance of one step movement distance. The microregion latent image measuring device according to item (2), characterized in that: ";
(4) “In the latent image pattern, the potential of an unexposed portion sandwiched between two V-shaped potential patterns is at least twice the distance of one step movement, and the maximum potential in this range The micro-region latent image measuring device according to item (3), wherein the exposure device (1) is controlled so that the difference in the minimum potential is within 100 V ”.
(5) “The minute area latent image measurement device according to any one of (1) to (4), wherein the exposure device (1) is a line beam laser”;
(6) “The exposure unit (2) is a line beam, and the length of the line beam in the main scanning direction is a line beam laser shorter than the length of the line beam of the exposure unit (1) in the main scanning direction. A microregion latent image measuring device according to any one of claims 1 to 5, "
(7) “Because the optical power output of the line beam laser of the exposure device (1) reaches an exposure energy equal to or lower than the required exposure energy of the target photoconductor, preferably 1/2 or less. The small area latent image measuring device according to any one of (1) to (6), which is controlled. "
Here, the “necessary exposure energy” described in the above item (7) in the present invention means the exposure energy required to attenuate from a predetermined charging potential (400 V or higher) to 100 V (absolute value notation). .

According to the first aspect of the present invention, it is possible to provide a minute area latent image measuring device capable of easily evaluating how the resolution characteristics of the photoconductor change with the load on the photoconductor.
Further, according to the second, third, and fourth aspects, the resolution characteristics of the photosensitive member can be easily evaluated.
According to the fifth aspect, the formation of the resolution evaluation latent image pattern is facilitated.
According to the sixth aspect of the present invention, it is possible to provide a minute area latent image measuring apparatus that enables accurate potential measurement.
Furthermore, according to claim 7, it is easy to create a latent image pattern whose resolution is easy to evaluate.

In the present invention, a charged photoconductor is exposed to form a line latent image pattern of 2 lines / mm or more in a minute width region, and a line beam laser is one-shot exposed to this latent image, and the surface is caused by light attenuation. A change in potential is caused, and a change in the amount of charge induced by an electrode placed in the vicinity of the photoconductor due to the change in potential, that is, an induced current (displacement current) is measured. The present invention relates to the application of a method for knowing the level of the surface potential.
Until now, a measuring instrument for measuring the surface potential of a photoconductor has been performed by a so-called vibration capacity type. In this measuring instrument, the gap between the photoconductor and the surface electrometer probe is usually 1 mm to 3 mm, but the area detected by the probe is 5 mm to 20 mm. From the viewpoint of spatial resolution, the area of 1 mm or less Potential measurement was impossible. Therefore, various techniques described above have been studied, but there are problems that are difficult to put into practical use, and diligent development efforts continue. An object of the present invention is to provide a method and an apparatus for evaluating the breakage of a latent image potential in a region of 1 mm width or less on a photoconductor on the basis of a method using light attenuation of a photoconductor. Another object of the present invention is to provide a micro area latent image pattern that can be easily evaluated by this method. The breakdown of the latent image potential is caused by forming a micro area latent image pattern on a photoconductor in an initial state (unused), measuring this with a measuring apparatus of the present invention, and then applying a load to the photoconductor to cause deterioration. Therefore, a minute area latent image pattern is formed again, and similarly measured and evaluated. From this result, it is possible to determine the resistance against the load of the photoreceptor. At this time, the fine area latent image pattern may be a single line-shaped potential attenuation portion having a width of 1 mm. However, if there are an exposed portion and an unexposed portion, it is easy to evaluate the shape of the pattern and the breakage. The above is preferable. In addition, the line shape makes it easy to use the evaluation of the displacement of the latent image as the resolution evaluation.

  This line pattern may be a rectangular potential attenuation, but it is preferable that a portion where the potential changes exists in the thickness direction of the line in order to evaluate the break with the potential. If the potential changes steeply, it is difficult to measure and reproduce the latent image pattern with the potential with the measurement resolution according to this method. More specifically, in order to reproduce the potential changing width with the potential measurement data, this width must be equal to or larger than the measurement step determined from the spatial resolution of the measurement device, and at least the measurement step ( More than twice the moving distance) is preferable. However, if it is made too large, the latent image width becomes large, which causes problems such as being unable to fit in a minute area, and taking time for measurement. Note that the measurement step cannot be made smaller than the beam size from the viewpoint of spatial resolution.

Also, the unexposed potential portion sandwiched between two line patterns should be flat to some extent in order to express the pattern with potential data, and is preferably at least twice the measurement step (movement distance).
That is, the width of the portion to be evaluated (portion to be expressed by potential data) is preferably at least twice the measurement step (movement distance). The upper limit is determined so as to be within 1 mm width.
The exposure device used for forming the latent image pattern can be realized by an imaging optical system, a beam scanning type writing optical system, or the like. However, in the method of the present invention, the line pattern needs to have a width of 1 mm in the rotation direction of the photosensitive member and a length (20 mm) or more of the detection light (line beam) in the axial direction of the photosensitive member. Although exposure with uniform illuminance is required, it is difficult to realize the optical system design because it requires some ingenuity. In addition, although exposure with a constant illuminance in the axial direction is easy with a beam scanning type exposure device, the polygon of the polygon is determined from the linear velocity of the photosensitive member, the resolution in the sub-scanning direction of writing (dpi), the number of mirror surfaces of the polygon, etc. It is necessary to determine the number of rotations (rpm) and set the timing of the exposure start beam in the main scanning direction, and it is also necessary to set the beam intensity for each line in the main scanning direction. Incorporation into a measuring device is difficult to use, for example, it is necessary to carry out with the same accuracy as control of the writing optical system. For this reason, it is preferable that a line beam laser is separately prepared and used as the exposure device used for forming the latent image pattern, similarly to the exposure device used as the detection light. In this case, a length is already secured in the photosensitive member axial direction (main scanning direction), and in the rotating direction (sub-scanning direction), the exposure width of the exposure unit is adjusted to 1 mm in accordance with the photosensitive member linear velocity. By determining the lighting time and controlling the light power within this time, a latent image pattern can be easily formed. At this time, the size (thickness) of the line beam laser in the sub-scanning direction is preferably equal to or less than the measurement step. However, the size of the line beam laser is the position where the maximum optical power is 1 / e ² (= 13.5%) from the definition of the size of the Gaussian beam laser. Therefore, it is different from the Gaussian beam. Actually, the bottom of the beam is poor, the beam has a wide size (thickness), and the exposure area becomes wider than the measurement step. Based on this, the target latent image pattern can be obtained by controlling the exposure power. Specifically, the “required exposure energy” of the target photoreceptor (here, “required exposure energy” is attenuated from a predetermined charged potential (400 V or more) to 100 V (absolute value notation) as described above. The exposure power required to provide this energy can be reduced to correct the spread of the exposure area due to poor hems and obtain a proper line pattern latent image. Was found. The same effect can also be obtained by shortening the time during which exposure is performed. As a method for shortening the exposure time, it is achieved by controlling the lighting time of the exposure device to shorten it or by increasing the linear velocity of the photosensitive member. The latter corresponds to giving energy smaller than the required exposure energy.
From the above, the obtained latent image pattern (explanatory diagram) is shown in FIG. The dotted rectangular line in the figure corresponds to the detection light from the exposure device (2).

  This is the reason why a line beam is used as the detection light in the measurement apparatus of the present invention. In the conventional technique using the optical attenuation, the measurement position is changed in a minute step in the rotation direction of the photosensitive member, and the exposure of the beam spot is performed. I was going. The measurement is repeated at different positions, and finally a one-dimensional profile of the latent image is obtained. However, in order to secure the spatial resolution of the measurement, it is necessary to reduce the beam used for potential detection. There is a problem in that the area where the occurrence of noise occurs is small, the signal obtained is small, and measurement is impossible. Possible solutions to this problem include (1) improvement of the signal processing circuit (amplifier circuit), (2) improvement of the S / N ratio by bringing the electrode closer to the photoconductor. In (1), there is known a means for repeatedly capturing the same signal with respect to a minute signal and superimposing it to ensure an S / N ratio, but it can be applied to a one-shot signal (meaning a single signal). However, this method is difficult due to the principle of measurement. The method (2) is effective, but even if the electrode-photoreceptor distance of 1 mm is 0.5 mm, it is only about twice as high, and the effect is small when the signal is buried in noise. In the present invention, since the measurement method is to measure a one-dimensional profile of the latent image in the rotation direction (sub-scanning direction) of the latent image, the detection light exposure size in the axial direction (main scanning direction) of the photosensitive member is increased, In other words, by increasing the region where the potential change occurs, the spatial resolution in the sub-scanning direction is ensured (the resolution in the main scanning direction is ignored), and the S / N ratio of the signal is improved.

  All measurements were performed with the apparatus configuration shown in FIG. The conductive electrode member is preferably formed by forming a transparent conductive thin film on transparent glass, which can be irradiated with light through the electrode when the glass electrode is opposed to the photoreceptor sample. Ease of use improves. The transparent glass may be general glass, but BK-7, quartz glass, and the like have a wide pass wavelength range and are preferable for measurement. In addition, ITO is generally used as the transparent conductive thin film, but there is no problem with other than this. The transparent conductive film can be formed on the entire surface of one side of the glass or in a mesh shape with a fine line (≦ 1 mm) using a pattern mask. Moreover, when the light to pass is a laser, it is preferable to attach an antireflection film to the glass on the laser incident side. This is to prevent so-called return light noise, in which the laser beam reflected from the glass surface on the laser incident side returns to the light emitting portion, forms a composite resonator, and the laser beam fluctuates. When this transparent electrode is placed opposite to the sample, the closer the distance to the sample, the greater the signal, which is preferable. However, the reflected light from the surface of the photoreceptor is reflected on the glass electrode surface and is expected to enter again. It is desirable to provide an antireflection film on the surface facing the photoconductor. The effect of reducing the spread of light can be expected.

More specific description will be given below.
<About device configuration>
The measuring apparatus has the configuration shown in FIG. 2, and operates by rotating the photosensitive drum, charging (using a scorotron charger), and writing using the exposure device (1) (exposure time = target writing width / photosensitive linear velocity). When the formed latent image arrives at the electrode part, the charging / rotation is stopped, and the exposure device (2) (line beam laser (main scanning direction) 20 mm × (sub-scanning direction) 24 μm−655 nm−) is irradiated as detection light. To do. When the induced current (displacement current) due to potential decay is measured, the photosensitive drum is rotated and moved (50 μm) to the next measurement position, and the next detection light is irradiated to measure the induced current (displacement current). This measurement is repeated until the entire latent image width is measured (FIGS. 2 and 3). The relationship between the charging potential and the magnitude of the induced current (displacement current) is investigated in advance, and the charging potential at that time is determined from the measured magnitude of the induced current (displacement current). This is used as the latent image width. By plotting against this, the one-dimensional profile of the latent image can be known.

<Example 1>
The experimental apparatus shown in FIG.
・ Charger: High voltage power supply for mains Trek 610C
Power supply for grid bias Matsusada Precision Co., Ltd. HJPM-1.5
・ Surface potential meter: Trek Model 344
・ Exposure tool (1): Global Laser's Lyte-MV laser line generator module, radiation angle 30 °,
Wavelength 635nm,
Focal length Adjust the optical system in the module so that it is at a position 83mm from the laser output end of the module. Exposure power control Linear modulation DC0 to 1V (at DC to 200kHz)
The output optical power is attenuated by the neutral density filter 1/125, and then 0 to 0.5 VDC
Lights in the range of. (See Figure 15)
Exposure time control (Latent image pattern width to be formed / Photoconductor linear velocity) + Adjust exposure time, Exposure power
Is controlled by an arbitrary waveform generator (Agilent Technology HP33220A)
According to the installation position Installed at an angle of 45 ° to the horizontal

・ Exposure tool (2): Ricoh Optical Co., Ltd. line beam laser wavelength: 655 nm
Line thickness 24μm
Line length 20mm
Focal length Distance between laser emitting end and photoconductor 74 mm-unique value of this exposure device (fixed)
Exposure energy Set by laser power x laser lighting time. Laser power is LD drive power
By flow. Here, the surface potential of 800 (-V) is attenuated to 100 (-V) as defined above.
“Necessary exposure energy” is exposed and the laser lighting time is 2 μs.
The laser power was set according to the sensitivity characteristics of the photoreceptor. All this
Exposure is performed under the following conditions.
・ Transparent conductive electrode: Substrate:
Quartz glass 10mm × 30mm × 1mmt
Surface facing the photoconductor Conductive electrode with antireflection film:
ITO (102.8) / SiO ₂ (103.15)
Back side (laser incident side) antireflection film:
Ta ₂ O ₅ (25.49) / SiO ₂ (38.15) / Ta ₂ O ₅ (86.74) / SiO ₂ (111.65)
Figures in parentheses are film thickness units in nm
All gaps with the photoreceptor were 0.1 mm.
・ Exposure device (2) trigger: Arbitrary waveform generator (Agilent Technologies HP33120A)
One shot pulse was generated and used as a trigger.
The generated pulse width was 2 μs.
Mounting position Horizontal position / Signal processing system: Current amplifier (KEITHLEY 428) + Oscilloscope (Yokogawa DL708)
-Controller: PC (self-made software), control of measurement device, data processing-Drum rotation device: Suruga Seiki Co., Ltd. precision rotation stage KS432-75
Driver D220
Resolution 0.0025 ° / pulse
Positioning accuracy 0.03 °
The rotation speed was set to 12.5 ° / s.
Photosensitive drum: A laminated OPC (organic optical semiconductor) drum manufactured by our company 60 mmφ × 334 mm long, and the exposure energy required for the potential attenuation from 800 (−V) to 100 (−V) is approximately 0.3 μJ at 655 nm. / Cm ² around.

Use this device,
(1): First, calibration curve data was measured for the photosensitive drum (unused product) to be measured.
The scorotron grid bias of the charger and the high voltage applied to the wire were sequentially changed. When the charging unit reached the electrode unit, the rotation was stopped and the detection light was irradiated. The detection light was irradiated six times, the first two data were discarded, and the average value of the remaining four data was used as the signal intensity obtained at the charged potential. The target charging potential is as follows. An example of the measured signal data is shown in FIG. 4, and an example of the obtained calibration curve data is shown in FIG. The measurement was performed at the timing shown in FIG. 3 with the exposure device (1) “latent image writing” disabled.
The following is the target charging potential.
900 (-V), 800 (-V), 700 (-V), 600 (-V), 500 (-V), 400 (-V), 300 (-V), 200 (-V), 100 ( -V)

(2): FIG. 6A and FIG. 6B show voltage data for controlling the optical power of the exposure device (1). In FIG. 6A, the horizontal axis is the time axis. In FIG. 6B, this is converted into data on the surface of the photosensitive member using the photosensitive member linear velocity data. Charging is started, and when the head of the charging unit is rotated by 270 °, the exposure device (1) is controlled by the data shown in FIG. Total exposure time is approximately 64ms. When the exposure start position reaches the horizontal position where the electrode is located, the rotation is stopped, and exposure is performed from the back surface of the transparent electrode by the exposure device (2) in 2 μs, and the current induced in the transparent electrode is detected. The signal that has passed through the current amplifier is acquired by a digital oscilloscope. The measurement position was moved in 50 μm steps (0.0955 ° rotation for a 60φ drum), and the measurement was repeated. The exposure device (2) was exposed 21 times. The first two batches were discarded, and the 19 measurement data were applied to the calibration curve data shown in FIG. 5 to read the corresponding surface potential. The results are shown in FIG. In FIG. 6, the distance between the two line patterns was aimed at 380 μm. In FIG. 7, it is measured at about 400 μm. Since the measurement position is changed in steps of 50 μm, it can be said that it is accurate if measured to 350 μm or 400 μm. It can be seen that two line pattern latent images formed within a width of 1 mm are measured.
Note that the reason for discarding the first two data during calibration curve data measurement and latent image pattern data measurement is that the circumferential size of the line beam of the exposure unit (2) is 24 μm, but the tail is completely cut off. This is because it affects 100 μm ahead.

<Comparative Example 1>
A 1 mmφ through-hole was provided in an Al-deposited PET film (thickness: 0.1 mm), and wound around an Al drum with the Al surface facing up. A voltage of 100 V was applied to the Al surface of the film. The Al drum was installed on the ground. In this state, using a commercially available vibration capacity type surface electrometer, scan the electrometer probe in the axial direction and circumferential direction of the drum while maintaining a gap of 0.5 mm, and collect data at a pitch of 0.1 mm And graphed. As shown in FIG. 8, the size of the pinhole is measured to about 2 mmφ, and the center of the pinhole, which should be 0 V potential, is also measured to about 55 V, and the conventional vibration capacitive surface potential meter has insufficient spatial resolution. It can be seen that it is impossible to measure a latent image within 1 mm.

<Example 2>
In the same manner as in Example 1, the calibration curve data of the photoreceptor (unused product) was measured, and then the initial latent image pattern was measured. Thereafter, the photoconductor was placed in an ozone atmosphere (5 ppm). Initial, one day later, two days later, and 4.5 days later, the latent image pattern was measured.
The results are shown in FIGS. 9-1, 9-2, 9-3, and 9-4. It can be seen that the latent image pattern is broken after 4.5 days. The feature is that the electric potential of the V-shaped line portion is shallow and the width of the V-shaped pattern is widened. The former can be seen as if the sensitivity characteristics of the photoconductor have deteriorated (sensitivity is slow), but if the “calibration curve data” that depends on the photosensitivity characteristics is re-acquired at this point, it is different from the initial one. There was almost no (refer FIG. 10). It is presumed that the electrostatic charge on the surface of the photoreceptor is low in surface resistance, and the latent image flows in the surface direction, not the deterioration of sensitivity. As the basis for this, when calculating the area of the V-shaped attenuation part in the figure (approximate), there is no big difference even after 4.5 days from the beginning, and there is a difference in the amount of charge that disappeared by exposure of the exposure device (1). It can be said that it is not. Also, when the “latent image distortion” seen within this 1 mm width occurs, the charging characteristics (ease of charging, charge retention ability in the dark) and sensitivity characteristics (light There was no change in the residual potential characteristics compared to the initial one (FIG. 11). It can be seen that characteristics of a minute region that cannot be captured by the conventional evaluation methods can be captured by the measurement apparatus of the present invention.

<Example 3>
(1) How to determine the exposure energy when creating one V-shaped latent image pattern:
Although the photoconductor is different from the conventional one, our laminated OPC was used. The exposure energy required for the potential attenuation from the charged potential 800 (−V) to 100 (−V) was approximately 0.23 μJ / cm ² at 655 nm.
The light power of the exposure device (1) line beam for making one V-shaped pattern with a width of 250 μm on this photoreceptor was determined as follows.
Exposure energy E received by one point on the photosensitive drum:
E = (line beam thickness) / v × (P (t) / beam area) (1)
The first half of equation (1) gives the time (s) during which one point on the drum is exposed.
The latter half of equation (1) gives the optical power density.
v is the drum linear velocity P (t) is the optical power (function of time)
Since the beam area is “line beam thickness × length”, E = 1 / v × P (t) / beam length P (t) is substituted into equation (1) to create the target latent image width. During the lighting time, it linearly increases from 0 to Pmax and then decreases linearly from Pmax to 0. Therefore, the average light power value during this exposure time is Pmax × (1/2).
Therefore, E = 1 / v × Pmax / beam length × (1/2)
The specific numbers are as follows:
v = 0.6545 (cm / s) (due to drum rotation speed of 12.5 ° / s and 60 mmφ drum)
Pmax = 1 (μW) (control voltage 0.125V, with neutral density filter 1/125)
Beam length = 3 (cm)
When calculating
E = 0.25 (μJ / cm ² )
And the value is not different from the required exposure energy defined in the present invention.

(2) Under this exposure condition, if writing is performed only for the time of a target latent image width of 250 μm (0.025 cm) / linear velocity of 0.6545 (mm / cm) = 0.038 (s), the latent image shown in FIG. The statue Bataan was obtained. The target of 250 μm is 500 μm. This was understood that there was a problem in the bottom of the writing beam, and the latent image width was increased (see FIG. 13). Therefore, when the exposure power of the exposure device (1) is halved, the latent image pattern shown in FIG. 14 is obtained. The width was improved to 400 μm.

It is a figure which shows the example of the latent image pattern written in this invention. It is a block diagram of the micro area | region latent image measuring device in this invention. It is a figure explaining the measurement timing in this invention. It is a figure which shows the example of the signal obtained by this invention. It is a figure which shows the example of the obtained calibration curve data. It is a figure which shows the example of the optical power control voltage of the line beam for latent image pattern formation in this invention. (The horizontal axis is the time axis.) It is a figure which shows the example of the optical power control voltage of the line beam for latent image pattern formation in this invention. (The horizontal axis is replaced with the “position” on the photoconductor.) It is a figure which shows the latent image electric potential data obtained by this invention. It is a figure which shows the comparative example of the spatial resolution by a commercially available surface potential meter. It is a figure which shows the latent image electric potential data by this invention of the initial stage before ozone bakuro. It is a figure which shows the latent image electric potential data by this invention one day after ozone bakuro. It is a figure which shows the latent image electric potential data by this invention 2 days after ozone bakuro. It is a figure which shows the latent image electric potential data by this invention after 4.5 days of ozone bakuro. It is a figure which shows the comparison of the analytical curve data of the initial stage in this invention, and 4.5 days after ozone bakuro. It is a graph which shows the macroscopic electrostatic characteristic of the photoconductor at the time of ozone baku by this invention. It is a figure which shows the example of the latent image pattern obtained by irradiation of "required exposure energy" in this invention of a photoreceptor. It is a figure which shows the optical power profile (thickness direction) data example of the line beam for latent image pattern formation in this invention. It is a figure which shows the example of the latent image pattern obtained by irradiation of 1/2 of "required exposure energy" by this invention of a photoreceptor. It is a figure which shows the control voltage versus optical power output example of the line beam for latent image pattern formation in this invention.

Claims (7)

Around the cylindrical photosensitive member, there are a charger, an exposure device (1) (latent image writing means), a transparent conductive electrode, an exposure device (2) (detection light exposure means) arranged on the back side thereof, and a static eliminator. Are arranged in this order. When the exposure device (1) forms a latent image pattern on the surface of the photosensitive member, and the pattern comes to the transparent conductive electrode portion, the rotational movement of the photosensitive member is stopped, and the exposure device ( In step 2), one shot pulse exposure is performed, a signal induced on the transparent conductive electrode as the charge on the photosensitive member is attenuated, and then the photosensitive member is exposed to a beam width in the circumferential direction of the exposure device (2) (hereinafter referred to as the beam width). In the measuring apparatus that moves in steps as described above and repeats signal sampling in the same manner, the latent image pattern formed by the exposure device (1) is at least 2 lines / mm or more in the photoconductor rotation direction. and controls the exposure device (1) such that the line patterns, each Rainpa The thickness direction of the potential shapes of the lines in the over emissions, minute area latent image measuring apparatus characterized by measuring, including the potential of the unexposed portion sandwiched the line. The micro exposure apparatus (1) according to claim 1, wherein the exposure apparatus (1) is controlled so that a line pattern of a latent image formed by the exposure apparatus (1) becomes a potential pattern attenuated in a substantially V shape. Area latent image measurement device. In the latent image pattern, the exposure device (1) is controlled so that the width of one side inclined portion of one V-shaped potential pattern becomes a distance that is twice or more of one step movement distance. The minute area latent image measuring device according to claim 2. In the latent image pattern, the potential of the unexposed portion sandwiched between the two V-shaped potential patterns is at least twice the distance of one step movement distance, and the difference between the maximum potential and the minimum potential in this range. 4. The microregion latent image measuring device according to claim 3, wherein the exposure device (1) is controlled so that the voltage is within 100V. 5. The minute area latent image measuring device according to claim 1, wherein the exposure device (1) is a line beam laser. The exposure device (2) is a line beam, and the length of the line beam in the main scanning direction is a line beam laser shorter than the length of the exposure device (1) in the main scanning direction. The microregion latent image measuring device according to any one of claims 1 to 5. The optical power output of the line beam laser of the exposure device (1) is controlled so that the exposure energy less than this energy, preferably 1/2 or less, reaches the “required exposure energy” of the target photoreceptor. The minute area latent image measuring device according to claim 1, wherein the latent image measuring device is a minute region latent image measuring apparatus.

Images