JP5116134B2 - Surface potential distribution measuring apparatus, latent image carrier and image forming apparatus - Google Patents

Description

  The present invention relates to a surface potential distribution measuring apparatus, a latent image carrier, and an image forming apparatus. More specifically, the present invention relates to a surface potential distribution measuring apparatus that measures a surface potential distribution of a sample by scanning a charged particle beam, and the surface potential distribution. The present invention relates to a latent image carrier evaluated by a measuring device, and an image forming apparatus including the latent image carrier.

  In an electrophotographic image forming apparatus such as a laser printer or a digital copying machine, light from a light source modulated in accordance with image information is condensed on a photoconductor via a scanning optical system, and a predetermined direction ( In the main scanning direction, an electrostatic latent image is formed on the photosensitive member. Then, toner is attached to the electrostatic latent image, and the toner is transferred onto paper or the like to form an output image.

  The electrostatic latent image formed on the photoconductor greatly affects the quality of the output image. Therefore, various methods and apparatuses for evaluating the electrostatic latent image formed on the photoreceptor have been proposed. The quality of the output image is improved by feeding back the evaluation result to the design of the image forming apparatus.

  For example, Patent Document 1 proposes a method of observing an electrostatic latent image by scanning a sample surface with an electron beam and using secondary electrons emitted by the scanning. However, in the method disclosed in Patent Document 1, since preparation for observation takes time, observation is possible if the sample can hold a charge semi-permanently like a normal dielectric. In ordinary photoconductors, since the charge cannot be held for a long time, for example, the electrostatic latent image disappears in the observation preparation stage, and accurate observation is impossible.

  Therefore, the applicant has proposed a method for measuring an electrostatic latent image even for a photoconductor that cannot hold charge for a long time (see, for example, Patent Documents 2 to 5).

  By the way, in recent years, digitization of image information has progressed rapidly, and the demand for further quality improvement of the output image of the image forming apparatus is increasing year by year. Along with this, further improvement in the evaluation accuracy of electrostatic latent images is desired.

Japanese Patent Laid-Open No. 3-49143 JP 2003-295696 A JP 2003-305881 A JP 2004-251800 A Japanese Patent Application Laid-Open No. 2004-233261

  The present invention has been made under such circumstances, and a first object of the invention is to provide a surface potential distribution measuring apparatus capable of measuring the surface potential distribution of a sample with high accuracy.

  A second object of the present invention is to provide a latent image carrier capable of carrying an electrostatic latent image with high accuracy.

  A third object of the present invention is to provide an image forming apparatus capable of forming a high quality image.

From a first aspect, the present invention is a surface potential distribution measuring apparatus that measures a distribution state of a surface potential of a sample by scanning a charged particle beam, the beam generating means for generating the charged particle beam; An optical system arranged between the beam generating means and the sample and focusing the charged particle beam from the beam generating means on the sample surface; at least a part of the charged particles arranged near the sample and passing through the sample A particle emitting member that emits a number of charged particles corresponding to the number of charged particles that have collided, a detection means that captures at least a part of the charged particles emitted from the particle emission member; based on the detection result, and processing means for determining the distribution of the surface potential of the sample; wherein the particles release components, the charged particle beam opening diameter is less 2mm passable And a surface potential distribution measuring apparatus is arranged between the sample and the optical system.

According to this, it becomes possible to accurately measure the surface potential distribution of the specimen.

  From the second point of view, the present invention satisfies the condition that the surface potential distribution is measured by the surface potential distribution measuring apparatus of the present invention, and the insulation resistance or resolution obtained from the measurement result is set in advance. Latent image carrier.

  According to this, since the insulation resistance or the resolution satisfies the preset conditions, the electrostatic latent image can be carried with high accuracy.

  From a third aspect, the present invention relates to the latent image carrier of the present invention; an optical scanning device that scans the latent image carrier; and an image formed on the latent image carrier. An image forming apparatus comprising: a transfer unit that transfers to an object.

  According to this, since the latent image carrier of the present invention is provided, it is possible to form a high-quality image.

<Surface potential distribution measuring device>
Hereinafter, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a schematic configuration of a surface potential distribution measuring apparatus 100 according to an embodiment of the present invention.

  A surface potential distribution measuring apparatus 100 shown in FIG. 1 includes an electron gun 10, a housing 30, a condenser lens (electrostatic lens) 35, a beam blanking electrode 37, an aperture 51, a stigmator 53, and a scanning lens (deflection electrode) 55. , An objective lens 57, a sample stage 81, a detector 91, an electron emission plate 93, a control system 3, a discharge system 83, a driving power source (not shown), and the like. In the present specification, the optical axis direction of each lens is referred to as a Z-axis direction, and two directions perpendicular to each other in a plane perpendicular to the Z-axis direction are described as an X-axis direction and a Y-axis direction.

  The electron gun 10 emits an electron beam. The electron gun 10 includes an emitter 11, an extraction electrode 31, an acceleration electrode 33, and the like.

  The extraction electrode 31 is disposed on the −Z side of the emitter 11, and a voltage for generating a strong electric field is applied to the emitter 11. Thereby, an electron beam is emitted from the tip of the emitter 11. In this embodiment, it is assumed that an electron beam is emitted in the −Z direction.

  The acceleration electrode 33 is disposed on the −Z side of the extraction electrode 31 and is applied with a voltage (referred to as an acceleration voltage Vacc) for applying desired energy to the electron beam emitted from the emitter 11.

  The condenser lens 35 is disposed on the −Z side of the acceleration electrode 33 and narrows the electron beam.

  The beam blanking electrode 37 is disposed on the −Z side of the condenser lens 35 and turns on / off the electron beam.

  The aperture 51 is arranged on the −Z side of the beam blanking electrode 37 and defines the beam diameter of the electron beam from the beam blanking electrode 37.

  The stigmator 53 is disposed on the −Z side of the aperture 51 and corrects astigmatism.

  The scanning lens 55 is disposed on the −Z side of the stigmator 53 and deflects the electron beam from the stigmator 53.

  The objective lens 57 is disposed on the −Z side of the scanning lens 55 and focuses the electron beam from the scanning lens 55 on the surface of the sample 71 through the beam emission opening 61.

  Hereinafter, an optical system including the condenser lens 35, the beam blanking electrode 37, the aperture 51, the stigmator 53, the scanning lens 55, and the objective lens 57 is also referred to as an electron beam optical system 5.

  A sample 71 is placed on the sample table 81 and can be moved two-dimensionally in the XY plane by a drive mechanism (not shown). The sample stage 81 has conductivity and is grounded. The surface shape of the sample 71 may be a flat surface or a curved surface.

  The electron emission plate 93 travels in the opposite direction to the detector 91 and the optical axis of the electron beam optical system 5 so that at least a part of the electrons to be detected that are not drawn into the detector 91 collide with the surface. When the electrons collide with the surface of the detector 91, the secondary electrons are emitted. Since the secondary electrons have low energy, the secondary electrons can reach the detector 91 by the pull-in voltage of the detector 91. The electron emission plate 93 has conductivity and is grounded. As a result, charge accumulation is suppressed, the energy of secondary electrons is suppressed low, and the secondary electrons are easily drawn into the detector 91. The emitted electrons from the electron emission plate 93 are secondary electrons when the incident electrons hit, tertiary electrons when the secondary electrons hit, and quaternary electrons when the tertiary electrons hit. These are called secondary electrons.

  Here, electron emission is performed so that a large difference does not occur between the detection result when the detection target electrons reach the detector 91 directly and the detection result when the electrons reach the detector 91 via the electron emission plate 93. The secondary electron emission ratio of the plate 93 is desirably 0.5 or more and 2 or less. As an example, the secondary electron emission ratio in Al (aluminum), Cu (copper), Ag (silver), Au (gold), and Si (silicon) is shown in FIG. The secondary electron emission ratio depends on the energy of incident electrons. Here, the energy of the incident electrons may be considered as a potential difference (absolute value) between the surface potential of the sample and the surface potential of the electron emission plate 93 (here, 0 V). For example, if the surface potential of the sample is −1000 V, the potential difference is 1000 V, and the detection target electrons enter the electron emission plate 93 with an energy of 1 keV. The secondary electron emission ratio at this time is 1.5 for Al, 1.2 for Cu, 1.4 for Ag, 1.6 for Au, and 1.0 for Si, and Cu and Si are particularly suitable. . If the potential difference is 2000V, the detection target electrons enter the electron emission plate 93 with energy of 2 keV. The secondary electron emission ratio at this time is 0.95 for Al, 0.8 for Cu, 1.0 for Ag, 1.25 for Au, and 0.65 for Si, and Ag is particularly suitable. If the potential difference is 600 V, the detection target electrons enter the electron emission plate 93 with an energy of 0.6 keV. The secondary electron emission ratio at this time is 2.3 for Al, 1.7 for Cu, 1.75 for Ag, 1.7 for Au, and 1.25 for Si, and Al is not suitable.

  As an example, as shown in FIG. 3, a power source 95 for applying a voltage to the electron emission plate 93 may be further provided to optimize the secondary electron emission ratio. For example, when the electron emission plate 93 is made of Cu and the incident electron energy at which the secondary electron emission ratio is 1 is 750 eV, and the surface potential of the sample 71 is −1000 V, the electron emission plate 93 is −250 V. By applying this voltage, the secondary electron emission ratio becomes 1, and a suitable image contrast can be obtained.

  Returning to FIG. 1, the detector 91 is arranged in the vicinity of the sample 71 and repels electrons near the surface of the sample 71 before reaching the surface of the sample 71 (in this specification, “primary repulsive electrons”). A part of the secondary electrons emitted from the electron emission plate 93. That is, in the present embodiment, as an example, primary repulsive electrons are detection target electrons. As the detector 91, a scintillator, a photomultiplier tube, or the like is used. Further, a positive voltage (for example, 10 kV) is applied to the detector 91 in order to increase detection sensitivity.

  The electron gun 10, the electron beam optical system 5, the electron emission plate 93, the sample table 81, and the detector 91 are accommodated in the housing 30. The housing 30 is composed of a lens barrel in which the electron gun 10 and the electron beam optical system 5 are accommodated, and a vacuum chamber in which the electron emission plate 93, the sample stage 81, and the detector 91 are accommodated. Yes.

  The exhaust system 83 is composed of a plurality of exhaust devices and places the inside of the housing 30 in a high vacuum state. Here, air is exhausted from below the housing 30 (−Z side), but is not limited thereto. Moreover, you may exhaust from several places.

  The control system 3 includes a computer, an input device, a display device, a printer device, and the like. The computer controls the electron gun 10, the electron beam optical system 5, the sample stage 81, the exhaust system 83, and the like according to a preinstalled program, and the sample 71 based on the output signal of the detector 91. The surface potential distribution is obtained. In the present embodiment, as an example, the surface potential of the sample 71 is assumed to be negative.

  Here, the relationship between the acceleration voltage Vacc of electrons irradiated to the sample 71 (hereinafter also referred to as “incident electrons”) and the surface potential potential of the sample 71 is described with reference to FIGS. 4A and 4B. explain. 4A and 4B are simplified for the sake of clarity. Here, the surface potential potential at the position irradiated with the incident electrons on the surface of the sample 71 is Vp (<0). Therefore, it can be considered that the voltage Vp is applied between the point B and the surface of the sample 71. In FIGS. 4A and 4B, the potential is illustrated as electrical potential energy of the unit charge.

  The incident electrons are not affected by the surface potential potential Vp in a section where the potential potential is 0 (V) (between AB), and are directed toward the surface of the sample 71 at a speed corresponding to the acceleration voltage Vacc (−Z direction). Move to. After the point B, the incident electrons are affected by the surface potential potential Vp.

  The influence of the surface potential potential Vp on the incident electrons is greatly different depending on the magnitude relationship between the acceleration voltage Vacc and the surface potential potential Vp.

(1) In the case of | Vacc |> | Vp | In this case, as shown in FIG. 4 (A), although the speed of the incident electrons gradually decreases after passing the point B, most of the incident electrons are incident. The electrons reach the surface of the sample 71. Therefore, as shown in FIG. 5A as an example, the detector 91 does not detect primary repulsive electrons.

(2) In the case of | Vacc |> | Vp | In this case, as shown in FIG. 4 (B), the incident electrons are gradually decelerated after passing point B, 0 before reaching. Then, starting from that point, the process proceeds in the direction away from the surface of the sample 71 (+ Z direction). That is, the velocity vector of the incident electrons in the Z-axis direction is reversed before reaching the surface of the sample 71, and the incident electrons return without reaching the surface of the sample 71. A part of the incident electrons that have not reached the surface of the sample 71 are detected by the detector 91 as primary repulsive electrons as shown in FIG. 5B as an example. Further, the primary repulsive electrons traveling toward the electron emission plate 93 collide with the electron emission plate 93 to emit secondary electrons, and the secondary electrons are detected by the detector 91.

  For example, “reflected electrons” used for observation and analysis in a scanning electron microscope (SEM), etc. are “scattered inside the sample surface or a little inside, and some of these electrons escaped into space. ("Surface analysis dictionary" p235 edited by the Surface Science Society of Japan, Kyoritsu Publishing Co., Ltd., published in 1986), which is completely different from "primary repulsion electron" in this specification.

  Next, a method for measuring the surface potential distribution of the sample 71 using the surface potential distribution measuring apparatus 100 configured as described above will be described with reference to FIGS. 6 to 8C. The flowchart in FIG. 6 is a process performed by an operator, and the flowchart in FIG. 7 is a process performed by a computer of the control system 3. It is assumed that the surface of the sample 71 is scanned two-dimensionally in the XY plane.

  In the first step 401, the sample 71 on which a latent image is formed is placed on the sample table 81.

  In the next step 403, the exhaust system 83 is operated and the inside of the housing 30 is brought into a high vacuum state.

  In the next step 405, the computer constituting the control system 3 is instructed to measure the surface potential distribution. Then, the process performed by the operator ends.

  When the computer constituting the control system 3 receives an instruction to measure the surface potential distribution, in the first step 501, the computer sets an initial value 1 to a counter i in which the number of repetitions is stored.

  In the next step 503, the acceleration voltage Vacc is set to a preset initial value.

  In the next step 505, a contrast image is captured (see FIGS. 8A and 8B). The white area in the contrast image is an area where the detection amount by the detector 91 is large, and the black area is an area where the detection amount by the detector 91 is small. The boundary between the white area and the black area is where the output signal of the detector 91 changes greatly. In the case of Vacc = −750V (see FIG. 8B), since the velocity of incident electrons is faster than in the case of Vacc = −600V (see FIG. 8A), the region where the incident electrons are inverted is reduced. And the black area is increasing.

  In the next step 507, the contrast image is binarized to obtain binarized data. For example, when measuring the distribution state of the surface potential in the X-axis direction and the Y-axis direction, binarized data is acquired in the X-axis direction and the Y-axis direction.

  In the next step 509, the diameter of the latent image is calculated based on the binarized data. For example, when measuring the distribution state of the surface potential in the X-axis direction and the Y-axis direction, the diameter of the latent image is calculated in the X-axis direction and the Y-axis direction. The diameter of the latent image calculated here is stored in a memory (not shown) in association with the acceleration voltage Vacc.

  In the next step 511, it is determined whether or not the value of the counter i is equal to a preset value N (an integer greater than or equal to 2). If the value of the counter i is not equal to N, the determination here is denied and the routine proceeds to step 513.

  In this step 513, 1 is added to the value of the counter i.

  In the next step 515, a preset increment (referred to as Δv) is added to the current value of the acceleration voltage Vacc. Then, the process returns to step 505.

  Thereafter, the processes in steps 505 to 515 are repeated until the determination in step 511 is affirmed.

  When the value of the counter i becomes equal to N, the determination at step 511 is affirmed, and the routine proceeds to step 521.

  In this step 521, as shown in FIG. 8C as an example, based on the data indicating the surface potential distribution stored in the memory (the diameter of the latent image for each acceleration voltage Vacc), the surface potential distribution profile. Is calculated.

  In the next step 523, the calculation result is displayed on the display device. And the acquisition process of surface potential distribution is complete | finished. FIG. 8C shows a potential distribution profile in the X-axis direction. In this case, the potential of the center (x = 0) of the latent image is about −520V, and the potential increases in the negative direction toward the outside. In the peripheral portion where | x | = 0.1 mm or more, about −830V. It turns out that it is about. Here, the operator can instruct the direction of the potential distribution profile displayed on the display device. It is also possible to display the potential distribution profile three-dimensionally. Furthermore, the calculation result can be printed by a printer.

  Further, according to the request of the operator, the surface charge distribution and the surface charge distribution profile of the sample 71 may be obtained based on the measurement result.

  Here, an example of a method for forming an electrostatic latent image on the surface of the photoconductor when the photoconductor as the sample 71 is used will be described. For example, as shown in FIG. 9A, the photoreceptor is an undercoat layer (hereinafter referred to as “UL”), a charge generation layer (hereinafter referred to as “CGL”), a conductive support, and the like. A charge transport layer (hereinafter referred to as “CTL”) is sequentially stacked. When the surface of the photoreceptor is charged and exposed in the presence of charges (hereinafter also referred to as “charged charges”), light is absorbed by the CGL charge generating material as shown in FIG. 9B as an example. Then, positive and negative charge carriers are generated. One of these carriers is injected into the CTL and the other into the conductive support by an electric field. Carriers injected into the CTL move to the surface of the CTL by an electric field in the CTL, and are combined with charges on the surface of the photoreceptor to disappear (see FIG. 9C). Note that UL is a so-called hole block layer and has a function of preventing charge injection from the conductive support. Thereby, a charge distribution, that is, an electrostatic latent image is formed on the surface of the photoreceptor.

  As is clear from the above description, in the surface potential distribution measuring apparatus 100 according to the present embodiment, the processing means is realized by the computer constituting the control system 3 and the program executed by the computer. It should be noted that at least a part of processing means realized by processing according to a program by a computer may be configured by hardware, or all may be configured by hardware.

  In this embodiment, the electron gun 10 constitutes a beam generating means, the electron beam optical system 5 constitutes an optical system, the electron emission plate 93 constitutes an electron emitting member, and the detector 91 constitutes a detecting means. Has been.

  As described above, according to the surface potential distribution measuring apparatus 100 according to the present embodiment, the electron gun 10 that generates an electron beam and the electron gun 10 disposed between the electron gun 10 and the sample 71 are arranged to emit electrons from the electron gun 10. An electron beam optical system 5 that focuses the beam on the surface of the sample 71, an electron emission plate 93 that is disposed in the vicinity of the sample 71 and emits secondary electrons in response to electrons via the sample 71, and is disposed in the vicinity of the sample 71. A detector 91 for detecting secondary electrons emitted from the electron emission plate 93 and a control system 3 for obtaining a distribution state of the surface potential of the sample 71 based on the detection result of the detector 91 are provided. Here, the surface of the sample 71 is scanned with an electron beam emitted from the electron gun 10 for each acceleration voltage for various acceleration voltages. Then, not only the primary repelled electrons that are repelled in the vicinity of the surface of the sample 71 before reaching the surface of the sample 71, but also the primary repelled electrons collide with the electron emitting plate 93 and are emitted from the electron emitting plate 93. Secondary electrons are also detected by the detector 91. As a result, the amount of information used to determine the surface potential distribution is increased, so that the S / N ratio of the output signal of the detector 91 is improved and density unevenness in the contrast image is suppressed. Both surface potential distribution and surface charge distribution can be accurately measured. In particular, it is possible to measure an electrostatic latent image on the order of microns.

  Further, according to the surface potential distribution measuring apparatus 100 according to the present embodiment, since the primary repulsive electrons are the detection target electrons, the potential depth can be quantitatively measured, and the potential distribution can be measured with high accuracy. It becomes possible.

  Further, according to the surface potential distribution measuring apparatus 100 according to the present embodiment, since the secondary electron emission ratio of the electron emission plate 93 is 0.5 or more and 2 or less, a suitable image contrast can be obtained. .

  In the above embodiment, the case where the electron emission plate 93 is disposed to face the detector 91 has been described, but the present invention is not limited to this. For example, as shown in FIGS. 10 and 11, the electron emission plate 93 has an opening through which incident electrons can pass, and is between the electron beam optical system 5 and the sample 71 and faces the sample 71. May be arranged.

  In this case, as shown in FIG. 12 (A) and FIG. 12 (B) as an example, the electron emission plate 93 includes an emission particle generating member 93a and an attachment portion (attachment screw) 93b. By making 93a into a thin disk shape, the arrangement space can be easily secured in the vacuum chamber of the housing 30, and the discharge between the detector 91 and the emitted particle generating member 93a can be achieved by reducing the number of corners. Can be suppressed. In FIG. 12A, the control system is omitted.

  In this case, the diameter of the opening of the electron emission plate 93 (hereinafter also referred to as “opening diameter” for convenience) is set to 2 mm or less, so that the primary repulsive electrons that should originally reach the detector 91 become the beam emission opening. Returning to 61 can be suppressed, and the S / N ratio of the output signal of the detector 91 can be improved. A smaller aperture diameter can suppress the entry of emitted electrons (secondary electrons in this case) into the beam exit opening 61, but if it is too small, the incident charged particles (here incident electrons) are suppressed. Limited to scanning area. For this reason, in order to ensure the minimum scanning area, it is desirable that the opening diameter is 0.1 mm or more. Incidentally, the beam emission opening 61 usually has an opening diameter of 5 mm or more.

  In this case, the emitted particle generating member 93a preferably has a flat surface shape with high smoothness on the surface on which charged particles (here, primary repulsive electrons) collide. If there are irregularities on the surface of the emitted particle generating member 93a, the amount of secondary electrons generated therefrom will vary, affecting the contrast image. By polishing the surface and increasing the surface accuracy, the amount of secondary electrons becomes uniform, and image noise can be reduced. The surface accuracy is desirably a surface roughness Ra of 0.8 μm or less. In order to improve the smoothness of the surface, it is desirable to polish the surface to give a mirror finish. In this case, the material is preferably copper or aluminum. Copper and aluminum are suitable for polishing the surface to increase the smoothness, but the amount of secondary electrons emitted is insufficient. The secondary electron emission ratio is preferably 0.8 or more, and more preferably 1 or more. The relationship between the incident electron energy and the secondary electron emission ratio is shown in FIG. If the acceleration voltage used for measurement is about 2 kV, the surface treatment (coating) is preferably performed with a material having a secondary electron emission ratio of 0.8 or more. However, if the secondary electron emission ratio is too high, the amount of secondary electron emission is amplified when a phenomenon occurs in which the emitted electrons reach the emission particle generating member 93a again. Therefore, the secondary electron emission ratio is 2 The following is desirable. Gold plating or the like is suitable. Silver plating is preferable although the secondary electron emission ratio is lower than gold plating. As a result, it is possible to align the signal when the primary repulsive electrons directly reach the detector 91 and the signal due to the secondary electrons generated once by colliding with the emitted particle generating member 93a, thereby obtaining a high-quality image. be able to.

  In this case, it is necessary to pay attention to the back surface (the surface opposite to the surface on which the primary repulsive electrons collide) of the emitted particle generating member 93a to which the primary repulsive electrons do not reach. If the material of the emitted particle generating member 93a is aluminum, an insulating film is formed by oxidation, and charges may be accumulated in the emitted particle generating member 93a. In this case, the trajectory of the incident electrons is affected, and not only the image is distorted but also discharge may occur. Accordingly, surface treatment for forming a conductive film is preferably performed even on the back surface. As the surface treatment, electroless nickel plating having excellent corrosion resistance is desirable. Thereby, accumulation of electric charges in the emitted particle generating member 93a can be prevented, and image distortion and discharge due to the bending of the trajectory of incident electrons can be suppressed, and a good state can always be maintained.

  In this case, as shown in FIGS. 10 and 11, it is desirable that the emitted particle generating member 93a is grounded. As an example, as shown in FIG. 14, the beam emission opening 61 and the opening of the electron emission plate 93 may be common. In addition, a dedicated conductive member that easily generates electrons may be disposed. Further, the emitted particle generating member 93a may be tilted toward the detector 91 so that emitted electrons (here, secondary electrons) can easily reach the detector 91.

  In this case, the electron emission plate 93 is placed between the electron beam optical system 5 and the sample 71 and covers a prospective angle of 30 degrees or more with respect to the optical axis of the electron beam optical system 5. When arranged opposite to 71, many primary repulsive electrons collide with the electron emission plate 93, so that the sensitivity of the entire measurement region can be kept uniform. Further, since the prospective angle is symmetric with respect to the optical axis of the electron beam optical system 5, the image quality can be improved.

  Further, in this case, as shown in FIG. 15 as an example, the electron emission plate 93 may have a magnetic shaft. Thereby, the influence of an external magnetic field can be suppressed and the bending of incident electrons can be suppressed. In addition, since the electron emission plate 93 is close to the sample 71, the angle of view can be widened even in the same area.

  Further, as shown in FIG. 16 as an example, an electron emission plate 94 equivalent to the electron emission plate 93 is further arranged in the vicinity of the sample 71 so that primary repulsive electrons repelled at a large angle collide. Also good. This makes it possible to detect primary repulsive electrons repelled almost directly, and a very wide range can be measured.

  As an example, as shown in FIG. 17, a configuration may be adopted in which substantially the entire area of the sample 71 is covered and an opening is provided only in a region where incident electrons pass and reach the detector 71. As a result, almost all of the primary repulsive electrons can be converted into secondary electrons and detected, so that the S / N ratio can be further improved.

  Moreover, although the said embodiment demonstrated the case where the acceleration voltage Vacc was changed, this invention is not limited to this. For example, the bias voltage (Vsub) may be applied to the sample 71, the acceleration voltage Vacc may be constant, and the bias voltage Vsub may be changed. Specifically, as shown in FIG. 18 as an example, an electrode 85 may be formed on the sample stage 81, and a power source 86 for applying Vsub to the electrode 85 may be further provided. Thereby, for example, when Vacc = −1800 V and Vsub = −1250 V, the same contrast image as that obtained when Vacc = −650 V in the above embodiment is obtained. When Vacc = −1800V and Vsub = −1100V, the same contrast image as that obtained when Vacc = −700V in the above embodiment is obtained.

  In the above embodiment, the case where the sample on which the latent image is formed is set in the surface potential distribution measuring apparatus has been described. However, the latent image may be formed on the sample in the surface potential distribution measuring apparatus. In this case, the surface potential distribution measuring device has a function of forming a latent image. Thereby, surface potential distribution measurement in real time becomes possible.

  As an example, FIG. 19 shows a surface potential distribution measuring apparatus 200 having a function of forming a latent image. In this surface potential distribution measuring apparatus 200, a pattern forming apparatus 220 for irradiating the surface of a sample 71 to form a latent image pattern is added to the surface potential distribution measuring apparatus 100 in the above embodiment. In FIG. 19, the control system is omitted.

  A pattern forming apparatus 220 in FIG. 19 includes a semiconductor laser 201 that emits light of a wavelength having sensitivity with respect to the sample 71, a collimating lens 203, an aperture 205, and an imaging lens including three lenses (207, 209, and 211). I have. Further, in the vicinity of the sample 71, an LED 213 for discharging the surface of the sample is disposed. The pattern forming device 220 and the LED 213 are controlled by a control system (not shown). Note that the optical system of the pattern forming apparatus 220 is adjusted so as to form a desired beam diameter and beam profile.

  A method for forming a latent image in the surface potential distribution measuring apparatus 200 will be briefly described.

(1) The LED 213 is turned on, and the surface of the sample 71 is neutralized.

(2) The surface of the sample 71 is uniformly charged using an electron beam emitted from the electron gun 10. Here, by setting the acceleration voltage to a voltage higher than the voltage at which the secondary electron emission ratio becomes 1, the amount of incident electrons exceeds the amount of emitted secondary electrons, so that electrons are accumulated in the sample 71 and charge up is performed. Wake up. As a result, the sample 71 is negatively charged. In addition, it can be charged to a desired potential by controlling the acceleration voltage and the irradiation time. FIG. 20 shows an example of a contrast image when the surface potential distribution is measured while the surface of the sample 71 is charged. As another charging means, contact charging, injection charging, or ion irradiation charging may be used.

(3) The semiconductor laser 201 is caused to emit light. Laser light from the semiconductor laser 201 becomes substantially parallel light by the collimator lens 203, is made a prescribed beam diameter by the aperture 205, and is then condensed on the sample surface by the imaging lens. Thereby, a latent image is formed on the sample surface.

  Therefore, in the surface potential distribution measuring apparatus 200, the electron gun 10, the electron beam optical system 5, the pattern forming apparatus 220, and the LED 213 constitute a latent image forming means.

  Note that a scanning mechanism using a galvano mirror or a polygon mirror may be attached to the optical system of the pattern forming apparatus 220. By adding a scanning mechanism, an arbitrary latent image pattern including a line pattern can be formed.

  Incidentally, the photoreceptor is required to have insulation resistance. Using the surface potential distribution measuring apparatus 200, it can be evaluated whether or not the sample 71 is causing electrostatic breakdown. And when the electrostatic breakdown has occurred, it can also identify where it has occurred. That is, the insulation resistance of the sample 71 can be evaluated.

  When the UL cannot withstand the electric field strength applied in the thickness direction of the photoreceptor, charge leakage occurs from the weakest point, and holes reach the surface. As a result, the negative charge on the surface of the photosensitive member is offset and a charge distribution is generated on the surface (see FIG. 21). Therefore, by scanning the charged photoconductor with an electron beam and detecting primary repulsive electrons and secondary electrons, whether or not electrostatic breakdown has occurred and where the electrostatic breakdown has occurred, Whether a leak has occurred can be specified on the micron order.

  Since the size of the toner is about 5 μm even if it is small, it can be considered that no charge leakage occurs if there is no charge leakage of 5 μm or more. Therefore, at least the photoreceptor required for the image forming apparatus is required to have no charge leakage of 5 μm or more when the electric field strength in the thickness direction is 10 V / μm or less.

In order to prevent background stains in the output image, when the electric field intensity applied in the thickness direction of the photoconductor is 30 V / μm to 40 V / μm and the electric charge is applied at about 1 × 10 ⁻⁸ coulomb / mm ² In addition, it is necessary that at least 99% of the insulating region be present.

  A method for evaluating the withstand voltage performance of the photoreceptor using the surface potential distribution measuring apparatus 200 will be described with reference to the flowchart of FIG. The flowchart in FIG. 22 is a process performed by a computer constituting the control system 3. When the computer constituting the control system 3 receives an instruction for evaluating the withstand voltage performance of the photoreceptor from the operator, it sets the start address of the program corresponding to the flowchart of FIG. 22 in the program counter.

In the first step 601, the photosensitive member is irradiated with an electron beam and charged. Here, the photosensitive member is charged under the conditions that the irradiation current is 1 × 10 ⁻⁹ A, the irradiation area is 1.47 mm ² , and the irradiation time is 4 minutes. That is, the total charge amount is 1.6 × 10 ⁻⁷ coulomb / mm ² .

  In the next step 603, the surface of the photoreceptor is scanned with an electron beam. Then, a signal output from the detector 91 during scanning is stored in a working memory (not shown).

  In the next step 605, when scanning is completed, two-dimensional image mapping is performed based on the output signal of the detector 91 stored in the working memory.

  In the next step 607, binarization processing is performed on the two-dimensional image map.

  In the next step 609, a charge leak point is specified.

  In the next step 611, the charge leak area is calculated.

  In the next step 613, the calculation result is displayed on the display device. Then, the withstand voltage performance evaluation process ends.

  It can be said that the smaller the area ratio of the region where charge leakage occurs, the higher the insulation resistance. As an example, in the case of the two-dimensional image map shown in FIG. 23, the charge leak area ratio is 1.2%, that is, the insulation resistance region is 88.8%, and it can be evaluated that the photoconductor is likely to cause scumming. . On the other hand, in the case of the two-dimensional image map shown in FIG. 24 as an example, the charge leakage area ratio is 0.4%, that is, the insulation resistance region is 99.6%, and the photoreceptor is excellent in insulation resistance. Can be evaluated.

  In this way, by evaluating the occurrence of charge leakage, it can be fed back to the design and the process quality of each process is improved, so that a photoconductor excellent in high image quality, high durability, high stability, and energy saving can be obtained. Can be provided. Further, by measuring the location of the charge leak, it is possible to analyze the occurrence and factors of the background contamination of the photoreceptor, which has been extremely difficult in the past. Then, by identifying the charge leak location and evaluating the quality, it is possible to provide a photoreceptor that achieves high durability and high image quality.

  Further, it is also possible to evaluate the resolution of the photosensitive member by partially changing the pattern forming device 220 of the surface potential distribution measuring device 200 as shown in FIG. 25 to be a pattern forming device 220 ′. . The pattern forming apparatus 220 ′ includes a semiconductor laser 201, a collimating lens 203, an aperture 205, an imaging lens 206, and the like. Then, a mask M is set on the optical path between the aperture 205 and the imaging lens 206. When the object distance of the mask M in the imaging lens 206 is L1 and the image distance is L2, the imaging magnification in the direction perpendicular to the optical axis of the imaging lens 206 is L2 / L1, and the mask M corresponding to this magnification An image of a pattern (hereinafter also referred to as “mask pattern”) is formed on the surface of the sample 71. That is, if L1 = L2, it is the same magnification. Further, if the inclination angle of the surface of the sample 71 with respect to the optical axis of the imaging lens 206 is θ and the inclination angle of the mask M with respect to the optical axis of the imaging lens 206 is α, the relationship L1 × tan α = L2 × tan θ is established.

  Here, as shown in FIG. 26 as an example, the mask pattern is a pair of basic patterns in which three identical rectangles are arranged at a predetermined pitch so that the longitudinal directions of the rectangles are orthogonal to each other. It consists of five basic pattern pairs (P1, P2, P3, P4, and P5), each of which has a size and a pitch that differ in stages. In FIG. 26, the white part is a light transmission part, and the black part is a light shielding part.

  Then, using two types of photosensitive members (photosensitive member A and photosensitive member B) charged under the same conditions as samples, the mask patterns were transferred to the respective photosensitive members under the same conditions to obtain respective potential contrast images. An example of a potential contrast image obtained from the photoreceptor A (hereinafter referred to as “contrast image A”) is shown in FIG. 27A, and an example of a potential contrast image obtained from the photoreceptor B (hereinafter referred to as “contrast image A”). FIG. 27B shows a contrast image B ”. In this contrast image B, in the transferred images of the basic pattern pair P1 and the basic pattern pair P2, the portions corresponding to the rectangles are connected to each other and are not separated. Therefore, the resolution of the photoreceptor B is at the level of the basic pattern pair P3. On the other hand, in the contrast image A, the portions corresponding to the rectangles are separated in the transfer image of the basic pattern pair P1 having the smallest pattern pitch. Therefore, the resolution of the photoreceptor A is equal to or higher than the level of the basic pattern pair P1.

  In this manner, a plurality of basic pattern pairs having different pitches can be transferred to the photoconductor, and the resolution of the photoconductor can be identified and evaluated from the obtained potential contrast image. In addition, by appropriately selecting the size, pitch, shape and the like of the mask pattern, it is possible to evaluate the characteristics of the electrostatic latent image formed on the photoconductor.

  For example, if the image forming apparatus has a writing density of 600 dpi, the required resolution of the photosensitive member is 42.3 μm (25.4 mm / 600), and if it is a 1200 dpi image forming apparatus, the resolution is 21.2 μm. It becomes. Therefore, if a pattern pitch twice 42.3 μm is transferred as a black and white pair and the pattern pitch can be identified in the obtained potential contrast image, it can be determined that the resolution of the photosensitive member. Therefore, in FIG. 26, if the width on the P1 photoconductor is 21.2 μm and the width on the P2 photoconductor is 42.3 μm, the photoconductor A has a resolution compatible with an image forming apparatus of 1200 dpi. However, it can be seen that Photoreceptor B does not have a resolution compatible with an image forming apparatus of 600 dpi. In this way, a photoreceptor capable of high-density writing can be obtained by grasping the resolution and feeding back to the design.

  Moreover, although the said embodiment demonstrated the case where a sample was plate shape, this invention is not limited to this, For example, a sample may be cylindrical. In this case, as an example, a latent image forming device may be provided like a surface potential distribution measuring device 250 shown in FIG. This surface potential distribution measuring apparatus 250 is obtained by adding a latent image forming apparatus to the surface potential distribution measuring apparatus 100 in the above embodiment. The latent image forming apparatus includes a charging unit 75, an exposure unit 76, and a charge removal unit 77. Here, the surface of the sample 71 is charged by the charging unit 75, and a latent image is formed by the exposure unit 76. After the surface potential distribution is measured, the surface of the sample 71 is neutralized by the neutralization unit 77. In this case, if the sample is a photosensitive drum used in an electrophotographic image forming apparatus such as a laser printer or a digital copying machine, image formation is performed by feeding back the measurement result of the surface potential distribution to the design of the image forming apparatus. The process quality of each process is improved, and high image quality, high durability, high stability, and energy saving can be realized. In FIG. 28, the control system is omitted.

  In this case, as shown in FIG. 29 as an example, the exposure unit 76 includes a semiconductor laser 110, a collimating lens 111, an aperture 112, a cylinder lens 113, two folding mirrors (114, 118), a polygon mirror 115, And two scanning lenses (116, 117) may be provided.

  The semiconductor laser 110 emits laser light for exposure. The collimating lens 111 makes the laser light emitted from the semiconductor laser 110 substantially parallel light. The aperture 112 defines the beam diameter of the light from the collimating lens 111. Here, by changing the size of the aperture 112, it is possible to set an arbitrary beam diameter in the range of 20 μm to 200 μm. The cylinder lens 113 shapes the light transmitted through the aperture 112. The folding mirror 114 bends the optical path of the light from the cylinder lens 113 in the direction of the polygon mirror 115. The polygon mirror 115 has a plurality of deflection surfaces, and deflects light from the folding mirror 114 at a constant angular velocity within a predetermined angle range.

  The operation of the exposure unit 76 will be briefly described. The light emitted from the semiconductor laser 110 is once imaged near the deflection surface of the polygon mirror 115 via the collimating lens 111, the aperture 112, the cylinder lens 113, and the folding mirror 114. The polygon mirror 115 is rotated in the direction of the arrow in FIG. 29 at a constant speed by a polygon motor (not shown), and the light imaged in the vicinity of the deflection surface is deflected at a constant angular velocity with the rotation. The deflected light scans the surface of the sample 71 via the two scanning lenses (116, 117) and the folding mirror 118. That is, the light spot moves in the longitudinal direction of the sample 71.

  Moreover, although the case where an electron beam was used as a charged particle beam was demonstrated in the said embodiment, not only this but an ion beam may be used. In this case, an ion gun is used instead of the electron gun. For example, when a gallium (Ga) liquid metal ion gun is used as the ion gun, the acceleration voltage is a positive voltage, and a bias voltage is applied to the sample 71 so that the surface potential is positive.

  In the above embodiment, the case where the surface potential of the sample is negative has been described. However, the surface potential of the sample may be positive. That is, the surface charge may be a positive charge. In this case, the sample may be irradiated with a positive ion beam such as gallium.

  In the above embodiment, the case where the surface potential distribution is obtained based on the primary repulsive electrons has been described. However, the present invention is not limited to this. For example, when there is no possibility of being affected by the material or surface shape of the sample, The surface potential distribution may be obtained based on the emitted secondary electrons. In this case, the secondary electrons from the sample and the secondary electrons from the sample collide with the electron emission plate 93, and thereby secondary electrons emitted from the electron emission plate 93 are detected by the detector 91. Will be detected.

  If there is a charge distribution on the sample surface, an electric field distribution corresponding to the surface charge distribution is formed in the space. For this reason, the secondary electrons generated by the incident electrons are pushed back by this electric field, and the amount reaching the detector is reduced. Accordingly, the exposed portion of the charge leak is black in the exposed portion and white in the non-exposed portion, and a contrast image corresponding to the surface charge distribution can be obtained. FIG. 30A shows the potential distribution in the space between the detector 91 and the sample with contour lines. The surface of the sample is in a state of being uniformly charged negatively except for the portion where the potential is attenuated due to light attenuation, and a positive potential is applied to the detector 91. Therefore, the potential indicated by the solid line In the contour line group, the potential increases as it approaches the detector 91 from the surface of the sample. Therefore, the secondary electrons el1 and el2 generated at the points Q1 and Q2 in FIG. 30A, which are negatively and uniformly charged portions in the sample, are drawn to the positive potential of the detector 91, and the arrows G1 and It is displaced as indicated by G2, and is captured by the detector 91.

  On the other hand, in FIG. 30A, the point Q3 is a portion where the negative potential is attenuated by light irradiation, and the arrangement of the potential contour lines is indicated by a broken line near the point Q3. In this partial potential distribution, the closer to Q3 point, the higher the potential. In other words, the secondary electron el3 generated in the vicinity of the point Q3 is subjected to an electric force constrained on the sample side as indicated by the arrow G3. For this reason, the secondary electron el3 is trapped in a potential hole indicated by a broken line potential contour and does not move toward the detector 91. FIG. 30B schematically shows the potential holes. That is, the intensity of secondary electrons (number of secondary electrons) detected by the detector 91 is such that the portion where the intensity is high is the ground portion of the electrostatic latent image (the portion that is uniformly negatively charged, FIG. 30A). Of the electrostatic latent image corresponds to the image portion of the electrostatic latent image (the portion irradiated with light, the portion represented by point Q3 in FIG. 30A). Will do.

  Therefore, if the output signal of the detector 91 is sampled at an appropriate sampling time, the surface potential distribution can be specified for each minute region corresponding to the sampling using the sampling time as a parameter. And, for example, if the intensity of the captured secondary electrons is expressed in terms of brightness, the image part of the electrostatic latent image is dark, the ground part is bright and contrasted, and as a bright and dark image according to the surface charge distribution It can be expressed (output). Furthermore, the surface charge distribution can be known from the surface potential distribution.

  Moreover, although the said embodiment demonstrated the case where the secondary electron discharge | released from the electron emission plate 93 was drawn in to the detector 91, it is not restricted to this, For example, the ion discharge | released from the electron emission plate 93 is detected by the detector 91. You may be drawn into. In this case, a negative pull-in voltage is applied to the detector 91.

<Image forming apparatus>
FIG. 31 shows a schematic configuration of a laser printer 500 as an image forming apparatus according to an embodiment of the present invention.

  The laser printer 500 includes a photosensitive drum 511, a charging roller 512, a developing device 513, a transfer roller 514, a cleaning device 515, a fixing device 516, an optical scanning device 517, a cassette 518, a registration roller pair 519, a paper feed roller 520, a discharge roller. A paper roller pair 522 and a tray 523 are provided.

  The charging roller 512, the developing device 513, the transfer roller 514, and the cleaning device 515 are disposed in the vicinity of the surface of the photosensitive drum 511, respectively. The charging roller 512, the developing device 513, the transfer roller 514, and the cleaning device 515 are arranged in this order along the rotation direction of the photosensitive drum 511.

  The photosensitive drum 511 is a latent image carrier that has been evaluated to have sufficient withstand voltage performance and compatible resolution as described above, and a photoconductive layer is formed on the surface thereof. ing. Here, the photosensitive drum 511 rotates at a constant speed clockwise (in the direction of the arrow) within the plane in FIG. 31 when image formation is performed.

  The charging roller 512 is a charging unit that uniformly charges the surface of the photosensitive drum 511. A “corona charger” can also be used as the charging means.

  The optical scanning device 517 irradiates the surface of the photosensitive drum 511 charged by the charging roller 512 with light LB modulated based on image information from a host device (for example, a personal computer), and performs exposure by optical writing. Do. As a result, on the surface of the photosensitive drum 511, the charge is lost only in the portion irradiated with light, and a latent image (electrostatic latent image) corresponding to the image information is formed on the surface of the photosensitive drum 511. The latent image formed here is a so-called negative latent image and moves in the direction of the developing device 513 as the photosensitive drum 511 rotates. The longitudinal direction (direction along the rotation axis) of the photosensitive drum 511 is referred to as “main scanning direction”, and the rotational direction of the photosensitive drum 511 is referred to as “sub-scanning direction”.

  The developing device 513 includes a toner cartridge in which toner is stored, and attaches toner only to a portion of the surface of the photosensitive drum 511 irradiated with light. That is, the developing device 513 makes the image information visible by attaching toner to the latent image formed on the surface of the photosensitive drum 511. Here, the latent image to which the toner is attached (hereinafter also referred to as “toner image”) moves in the direction of the transfer roller 514 as the photosensitive drum 511 rotates.

  The cassette 518 is detachable from the main body of the laser printer 500, and a transfer paper P as a transfer object is accommodated therein. The paper feed roller 520 is disposed in the vicinity of the cassette 518, and the paper feed roller 520 takes out the uppermost sheet of the transfer paper P stored in the cassette 518.

  The registration roller pair 519 is disposed in the vicinity of the transfer roller 514 and captures the leading end portion of the transfer paper taken out by the paper feed roller 520. The registration roller pair 519 feeds the transfer paper into the gap between the transfer roller 514 and the photosensitive drum 511 in accordance with the timing at which the toner image on the photosensitive drum 511 moves to the transfer position. The transferred transfer paper is superimposed on the toner image by the transfer roller 514, and the toner image is electrostatically transferred.

  The transfer paper onto which the toner image has been transferred is sent to the fixing device 516 where the toner image is fixed in the fixing device 516, passes through the conveyance path 521, and is discharged onto the tray 523 by the paper discharge roller pair 522.

  The surface of the photosensitive drum 511 after the toner image is transferred is cleaned by a cleaning device 515 to remove residual toner, paper dust, and the like.

  As described above, the laser printer 500 according to the present embodiment includes the photosensitive drum 511 that is evaluated to have a sufficient withstand voltage performance and a resolution that can be dealt with, so that a high-quality image is formed. It becomes possible to do. In addition, it is possible to realize an image forming apparatus that has excellent resolution and high definition, high durability, and high reliability.

It is a figure for demonstrating the surface potential distribution measuring apparatus which concerns on one Embodiment of this invention. It is a figure for demonstrating the secondary electron emission ratio of each substance. It is a figure for demonstrating the case where a voltage is applied to the electron emission board in FIG. 4A and 4B are diagrams for explaining the relationship between the acceleration voltage and the potential of the sample surface, respectively. FIG. 5A and FIG. 5B are diagrams for explaining the behavior of incident electrons by the acceleration voltage. It is a flowchart (the 1) for demonstrating the measuring method of surface potential distribution. It is a flowchart (the 2) for demonstrating the measuring method of surface potential distribution. 8A and 8B are diagrams for explaining a contrast image, and FIG. 8C is a diagram for explaining a potential distribution profile. FIG. 9A is a diagram for explaining the structure of the photoconductor, and FIGS. 9B and 9C are diagrams for explaining the formation of the potential distribution, respectively. It is a figure for demonstrating the modification 1 of the electron emission board in FIG. It is the figure which extracted a part of FIG. FIGS. 12A and 12B are diagrams for explaining the electron-emitting plate in FIG. It is a figure for demonstrating the relationship between the secondary electron emission ratio and acceleration voltage of each substance. It is a figure for demonstrating the surface potential distribution measuring apparatus which made the beam emission opening part and the opening part of an electron emission plate common. It is a figure for demonstrating the modification 2 of the electron emission board in FIG. It is a figure for demonstrating the modification 3 of the electron emission board in FIG. It is a figure for demonstrating the modification 4 of the electron emission board in FIG. It is a figure for demonstrating the bias voltage applied to a sample. It is a figure for demonstrating the modification 1 of the surface potential distribution measuring apparatus of FIG. It is an example of the contrast image of the charged sample. It is a figure for demonstrating an electric charge leak. It is a flowchart for demonstrating the evaluation method of a dielectric strength performance. It is FIG. (1) for demonstrating the contrast image obtained in evaluation of withstand voltage performance. It is FIG. (2) for demonstrating the contrast image obtained in evaluation of withstand voltage performance. It is a figure for demonstrating the optical system of the pattern formation apparatus suitable for evaluating the resolution of a photoreceptor. It is a figure for demonstrating the mask pattern used in evaluating the resolution of a photoreceptor. FIGS. 27A and 27B are diagrams for explaining a contrast image obtained from the photoconductor to which the mask pattern of FIG. 26 is transferred. It is a figure for demonstrating the modification 2 of the surface potential distribution measuring apparatus of FIG. It is a figure for demonstrating the exposure part in FIG. FIG. 30A and FIG. 30B are diagrams for explaining measurement of surface potential distribution using secondary electrons, respectively. It is a figure for demonstrating a laser printer provided with the photoreceptor to which the withstand voltage performance and the resolution were evaluated.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 3 ... Control system (processing means), 5 ... Electron beam optical system (optical system), 10 ... Electron gun (beam generation means), 76 ... Exposure part (latent image formation means), 91 ... Detector (detection means), 93 ... Electron emission plate (electron emission member), 95 ... Power source (voltage applying means), 100 ... Surface potential distribution measuring device, 200 ... Surface potential distribution measuring device, 220 ... Pattern forming device (latent image forming means), 250 ... Surface potential distribution measuring device, 511, photosensitive drum (latent image carrier), 517, optical scanning device, 514, transfer roller (transfer means), P, transfer paper (transfer object).

Claims (16)

A surface potential distribution measuring apparatus that measures a distribution state of a surface potential of a sample by scanning a charged particle beam,
Beam generating means for generating the charged particle beam;
An optical system disposed between the beam generating means and the sample and focusing the charged particle beam from the beam generating means on the sample surface;
A particle emitting member disposed in the vicinity of the sample, wherein at least some of the charged particles that have passed through the sample collide, and emit a number of charged particles according to the number of charged particles that have collided;
Detection means for capturing at least part of the charged particles emitted from the particle emitting member;
Comprising a,; based on the detection result of said detecting means, and processing means for obtaining the distribution state of the surface potential of the sample
The particle emitting member has an opening having a diameter of 2 mm or less through which the charged particle beam can pass, and is a surface potential distribution measuring device disposed between the optical system and the sample . The surface potential distribution measuring apparatus according to claim 1 , wherein a surface of the particle emitting member on which at least a part of charged particles through the sample collides is subjected to a gold plating process. The particle-emitting member, the surface potential distribution measuring apparatus according to claim 1 or 2, characterized in that it has a conductivity. The shape of the particle-emitting member, the surface potential distribution measuring apparatus according to any one of claims 1 to 3, characterized in that a disk shape. At least a portion collides surface, the surface potential distribution measuring apparatus according to any one of claims 1 to 4, characterized in that a smooth surface of the charged particles through the sample in the particle-emitting member. The conductive film is formed in the surface on the opposite side to the surface where at least one part of the charged particle through the said sample collides in the said particle | grain discharge | release member, The conductive film is formed in any one of Claims 1-5 characterized by the above-mentioned. The surface potential distribution measuring apparatus according to 1. The said particle | grain discharge | release member discharge | releases a secondary electron, when a charged particle collides, The secondary electron emission ratio is 0.5 or more and 2 or less, The any one of Claims 1-6 characterized by the above-mentioned. The surface potential distribution measuring apparatus described. The particle emitting member emits secondary electrons when charged particles collide, and the surface of the particle emitting member on which at least a part of charged particles through the sample collides has an acceleration voltage of the charged particle beam of 2 keV. The surface potential distribution measuring apparatus according to any one of claims 1 to 6 , wherein the surface potential distribution measuring apparatus is coated with a material having a secondary electron emission ratio of 0.8 or more and 2 or less. 9. The surface potential distribution measuring apparatus according to claim 7 , further comprising a voltage applying unit for applying a voltage to the particle emitting member and optimizing a secondary electron emission ratio thereof. The surface potential distribution according to any one of claims 1 to 9 , wherein the charged particles passing through the sample are charged particles repelled in the vicinity of the sample surface before reaching the sample surface. measuring device. Surface potential distribution measuring apparatus according to any one of claims 1 to 10, further comprising a latent image forming means for forming a latent image on the surface of the sample. A surface potential distribution is measured by the surface potential distribution measuring device according to any one of claims 1 to 11 , and a latent image satisfying a preset condition for insulation resistance obtained from the measurement result. Carrier. Conditions wherein is previously set, according to claim 12 where the electric field intensity applied in the thickness direction of the sample is at the 10V / [mu] m, charge leakage over size 5μm is characterized in that it is a, not detected The latent image carrier described in 1. The preset condition is that the electric field strength applied in the thickness direction of the sample is 30 V / μm or more and 40 V / μm or less, and the sample is irradiated with at least 1 × 10 ⁻⁸ coulomb / mm ^2. The latent image bearing member according to claim 12 , wherein 99% or more of an insulation-resistant region exists. A surface potential distribution is measured by the surface potential distribution measuring device according to any one of claims 1 to 11 , and a latent image obtained from the measurement result satisfies a preset condition. Image carrier. A latent image carrier according to any one of claims 12 to 15 ;
An optical scanning device for scanning the latent image carrier with light;
An image forming apparatus comprising: transfer means for transferring an image formed on the latent image carrier to a transfer object.