JP4878072B2 - Discharge unevenness measuring method, discharge unevenness observing method, and discharge unevenness observing apparatus - Google Patents

Description

  The present invention relates to a discharge unevenness measurement method, a discharge unevenness observation method, and a discharge unevenness observation apparatus, and more particularly to discharge unevenness observation for a sheet-like member used in an image forming apparatus using an electrophotographic method.

  An image forming apparatus using an electrophotographic system is equipped with various members for executing an image forming process. Among them, there is a transfer device as a member that utilizes a discharge and a charging phenomenon due to discharge.

  Hereinafter, a transfer belt which is one of the members used in the transfer apparatus will be described.

  In general, in an image forming process in a copying machine, a printer, or the like, a toner image developed on a photoreceptor is transferred to a transfer belt or paper by a transfer electric field formed between the photoreceptor and a transfer belt (including an intermediate transfer belt). Therefore, it is very important to grasp these electric characteristics when the transfer belt is manufactured or mounted on the image forming apparatus.

The electric characteristics of these belts are most commonly evaluated using surface resistivity or volume resistivity measured based on JIS K 6911 method.

  The surface resistivity is calculated by pressing an electrode (probe) against the surface of the sample as shown in FIG. 4 and detecting the current flowing through the surface, and the volume resistivity is the upper and lower electrodes of the sample as shown in FIG. It is obtained by measuring the current flowing between them.

  As another surface resistance measuring method, three contact terminals are brought into contact with a member to be measured, two of the terminals are electrically connected, and a resistance between the other one terminal is measured. A method of obtaining surface resistivity by measuring as a combined resistance in parallel has also been proposed (for example, Patent Document 1).

On the other hand, it is empirically known that there is a certain degree of correlation between the surface resistivity or volume resistivity of the transfer belt and the transferred image, and many belt members that actively control these values have been proposed. Yes. For example, a combination of an inner layer made of medium-resistance rubber, a dielectric layer, and a surface layer made of a material having a lower specific resistivity than that of the dielectric layer constitutes a transfer belt with three layers. A stable and good image is obtained (for example, Patent Document 2).
Also, an intermediate transfer belt manufacturing method that prevents unevenness of image by dispersing a plurality of types of carbons having different electrical conductivity so as to be unevenly distributed in the film thickness direction with respect to the resin and making the resistance of the belt surface higher than that of the back surface. Has been proposed (for example, Patent Document 3).

  By the way, the surface resistivity and the volume resistivity are evaluated using an electrode of the order of millimeter or more, and in order to show macro electric characteristics, the electric characteristics of the belt can be determined only by the measured values of the surface resistivity and the volume resistivity. There is a problem that it cannot be grasped completely.

  In the transfer process of an image forming apparatus, the discharge generated between the transfer material and the photoconductor, or between the transfer material and the transfer roller is an important factor, so the values of the surface resistivity and volume resistivity in a macro sense are Even if the toner on the photoconductor is transferred to a transfer belt or paper under the same conditions using an equivalent roller, the density unevenness that occurs in halftone images, etc. In the final stage of development of an image forming apparatus, a toner image transfer experiment is performed on various roller samples under various conditions, and an output image is seen to be a preferable roller. There has been work such as extracting. From this situation, it is desirable to establish a more microscopic evaluation method for electrical discharge characteristics and electrical characteristics. At the same time, based on the knowledge obtained there, a good transfer roller that does not cause density unevenness or white spots has been developed. It was requested to be done.

Further, an important characteristic as a transfer roller is how an electrically uniform nip portion can be formed in combination with a transfer material.
As an index to indicate the characteristics of the transfer roller used to date, a macro resistance value calculated from the current value that flows when a certain bias is applied between the core of the roller member and some counter electrode And the cell diameter measured using a microscope etc. is the main, the electrical characteristics of the roller member can not be completely grasped only by these characteristic values, and in the state where the roller member and the transfer material are in contact, Since the physical shape and viscoelastic distribution of the roller member surface are affected, there is a problem that it is not known whether or not an electrically uniform nip can be formed in the actual transfer nip portion.
As a result, even if the toner on the photosensitive member or the transfer belt is transferred under the same transfer conditions using another transfer roller having the same cell diameter or the resistance value obtained by the above-described method, the above-described white spots are detected. Problems such as different tendencies will occur frequently. Accordingly, in this case as well, as described above, an operation of extracting a preferable roller based on a transfer experiment has occurred in the development stage of the image forming apparatus.

  On the other hand, even in the case of a transfer belt, surface resistivity and volume resistivity are evaluated using an electrode in the order of millimeters as in the case of the transfer roller described above. There is a problem that the electrical characteristics of the belt cannot be completely grasped only by measured values of resistivity and volume resistivity. Further, in the transfer process of the image forming apparatus, since the discharge generated between the belt and the photoconductor or between the belt and the transfer roller is an important factor, not only the resistance but also the surface roughness of the belt is actually large. It is known that the toner has a similar surface resistivity and volume resistivity in the macro sense, and the toner on the photoconductor is transferred to a transfer belt or paper under the same conditions. However, there are many problems such as different tendency of white spots as described in the case of the transfer roller. As a result, in the development stage of the image forming apparatus, the toner image of various belt samples under various conditions. An operation of performing a transfer experiment and extracting a preferable belt by looking at an output image has occurred. From this situation, it is desirable to establish a more microscopic evaluation method for discharge characteristics and electrical characteristics. At the same time, based on the knowledge obtained there, a good transfer belt that does not cause density unevenness and white spots has been developed. It was requested to be done. The same applies to the selection of recommended paper by determining the adaptability of paper used in electrophotographic copying machines and printers.

  An object of the present invention is to provide a practical device capable of evaluating microscopic discharge characteristics and electrical characteristics for a sheet such as a transfer belt, in view of the problems in the above-described conventional members using discharge and the charging phenomenon due to discharge. It is to provide a measurement technique and a measurement apparatus.

  (1) The sheet member has a transparent electrode substrate in which a phosphor is coated on the surface of a translucent or transparent electrode, and the transparent electrode substrate has a phosphor coated surface directed toward the sheet member and A back electrode disposed at a position facing the transparent electrode substrate via the sheet member and an imaging photographing means disposed on the back surface of the transparent electrode substrate; A potential difference is provided between the transparent electrode substrate and the back counter electrode, and the fluorescence generated from the phosphor due to the discharge generated by the potential difference between the transparent electrode substrate and the sheet member is photographed by the imaging unit. And observing the discharge unevenness generated in the sheet member.

  (2) The imaging photographing unit is connected to a discharge unevenness evaluating unit, and the discharge unevenness evaluating unit extracts a characteristic amount of the discharge unevenness based on image data from the imaging printing photographing unit (1). ) Discharge unevenness measuring method.

  (3) The method for observing discharge unevenness according to (1) or (2), wherein the imaging photographing means uses a configuration in which an equal-magnification image sensor is disposed on the back surface of the transparent electrode substrate.

  (4) A discharge unevenness observation device comprising a mechanism for executing the discharge unevenness observation method according to any one of (1) to (3).

  According to the first and fourth aspects of the present invention, it is possible to directly observe the resistance unevenness of the sheet-like member such as the transfer belt and the copy sheet and the discharge unevenness due to the surface unevenness, and the discharge unevenness that affects the image is generated. Judgment is easy. In addition, a sheet-like member suitable for high image quality can be easily selected.

  According to the second aspect of the present invention, it is possible to objectively evaluate discharge unevenness by calculating a characteristic amount that can be uniquely determined.

  According to the third aspect of the present invention, the image pickup device can be disposed close to the phosphor screen, so that an image of the discharge light can be taken optically efficiently.

It is a schematic diagram for demonstrating the structure of the apparatus for observing the discharge nonuniformity for the sheet | seat material containing a transfer belt. It is a figure which shows the arrangement configuration of the current electrode and imaging means used for the observation apparatus shown in FIG. It is a block diagram for demonstrating the structure for performing evaluation used for the observation apparatus of a structure shown in FIG. It is a figure which shows the measurement structure for calculating the surface resistivity of a belt. It is a figure which shows the structure which measures the surface resistivity of a belt.

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

An embodiment relating to discharge unevenness observation for a sheet including a belt will be described.
FIG. 1 is a schematic diagram showing the configuration of a sheet discharge unevenness observation apparatus. In the figure, in the discharge unevenness observation apparatus, a sheet member 1003 to be measured is arranged in close contact with a back electrode 1004, and the sheet member A transparent electrode substrate 1001 is disposed on the substrate 1003 at an interval.

The phosphor 1002 is uniformly laminated on the surface of the transparent electrode substrate 1001 in the gap direction.
The transparent electrode substrate 1001 uses an ITO electrode, for example. The phosphor 1002 only needs to have good emission efficiency by electroluminescence. For example, if there is an emission peak in the vicinity of 550 nm as in P43, the visibility is high and visual observation is also possible.

  As the imaging unit 1005, a still or moving image camera using a CCD or CMOS sensor as an image sensor is used. In particular, when the real-time property is not important, it is possible to increase the sensitivity by taking an image with a long exposure time as a still image.

  In addition, a combination of a phosphor and an image sensor having a characteristic that the emission peak wavelength of the phosphor 1002 and the peak wavelength of the sensitivity of the image sensor coincide with each other may be appropriately selected. A voltage difference is applied between the transparent electrode substrate 1001 and the sheet member 1003 by applying a voltage between the transparent electrode substrate 1001 and the back electrode 1004 by manual voltage / current setting or by the power supply means 1006 controlled by the computer means 7. When an appropriate potential difference is generated, discharge occurs between the transparent electrode substrate 1001 and the surface of the sheet member 1003. The phosphor 1002 emits light by energy generated by the discharge. Depending on the surface shape, resistance, and dielectric constant unevenness of the sheet member 1003, discharge current unevenness occurs, and the emission intensity of the phosphor 1002 appears uneven. An image of emitted light is taken into the computer means 1007 by the image pickup means 1005 and appropriately subjected to image processing, and then displayed on the image display means 1008, whereby the discharge unevenness distribution can be observed.

FIG. 2 is a diagram showing a configuration in which an image sensor is arranged on the back surface of the transparent electrode substrate 1001. In FIG. A sensor 1010 is provided.
The same-size image sensor is a two-dimensional sensor such as a CCD sensor or a CMOS sensor and has an area of 1 cm 2 or more. Further, it may be changed so as to obtain a two-dimensional image by scanning a sheet member using a line sensor mounted with high density.
By disposing the image sensor close to the light emitting surface of the phosphor by discharge, an image can be taken optically efficiently.

FIG. 3 is a block diagram illustrating a process of evaluating discharge unevenness.
In FIG. 3, the raw image data 20 of light emission on the phosphor screen taken by the image pickup means 5 is converted into a quantity proportional to the physical light power by the gamma conversion means 21, and this is used as the light quantity distribution data 22. Further, discharge unevenness is evaluated by the unevenness evaluation means 23 based on the light quantity distribution data 22.

Methods for objectively evaluating the characteristics of discharge unevenness include RMS granularity, Wiener spectrum, R.D., and the like, which are conventionally used image noise evaluation methods. P. The unevenness is evaluated by appropriately modifying the granularity obtained by considering the visual frequency characteristics proposed by Dooley et al. (Reference: RP Dooley, R. Shaw, Journal of Applied Photographic Engineering, Vol. 5 (1979) 190-196.)
Specifically, the original RMS granularity is a standard deviation of image density, and the visual granularity by Dooley et al. Is a noise evaluation amount with respect to lightness, but in the present invention, it is replaced with an evaluation amount with respect to light quantity distribution data 1022. Furthermore, the two-dimensional light quantity data P normalized by the maximum value is used.

  The RMS granularity (σ) is evaluated by using Expression 1 for the two-dimensional light quantity data Pij obtained by discretizing the space. However, N is the number of data, and <P> is an average value of the light amount data Pij.

  The visual granularity (G) is expressed in a continuous space here, but the two-dimensional Fourier transform represented by Expression 2 is performed on the two-dimensional light quantity data P (x, y) to obtain the spatial frequency characteristic F.

  Next, it is converted into a Wiener spectrum WS by Equation 3. Here, (f, θ) is a music coordinate representation of the frequency space.

  Finally, the granularity G is calculated by Equation 4.

  Here, VTF (f) is a visual spatial frequency characteristic. In the definition of visual granularity by Dooley et al., Equation 4 is further multiplied by a correction coefficient based on the average value of the density distribution, but this is unnecessary here.

  Further, the relationship between the light quantity and the current density may be converted into a function in advance, and the light quantity distribution data may be converted into current density distribution data and applied to the RMS granularity and the visual granularity.

  Expression 1 is directly programmed, and Expressions (2) to (4) are programmed using a calculation algorithm obtained by discretizing the real space (x, y) and the frequency space (u, v), and are installed in the computer means 1007. By doing so, it can be realized.

  Conventionally, it is often performed to visually compare an appropriately produced rank sample with an evaluation target to determine whether the unevenness is good or bad. However, the discharge unevenness evaluation method and apparatus according to the present invention can be used to objectively evaluate the rank of discharge unevenness. Is possible.

DESCRIPTION OF SYMBOLS 1 Roller member used as sample 2 Bias electrode 3 Imaging means 4 Photoelectron multiplication means 7 Transparent electrode 1003 Sheet material

Real Fair 7-5419 JP-A-7-295391 Japanese Patent Laid-Open No. 11-109761

Claims (4)

  The sheet member has a transparent electrode substrate in which a phosphor is coated on the surface of a translucent or transparent electrode, and the phosphor electrode has a phosphor coated surface directed toward the sheet member and is not in contact with the sheet member. And a back electrode disposed at a position facing the transparent electrode substrate via the sheet member, and an imaging photographing unit disposed on the back surface of the transparent electrode substrate, the transparent electrode A potential difference is provided between the substrate and the back counter electrode, and the fluorescence generated from the phosphor by the discharge generated by the potential difference between the transparent electrode substrate and the sheet member is photographed by the imaging means, An uneven discharge measurement method for a sheet member, characterized by observing discharge unevenness generated in the sheet member.   The image capturing and photographing unit is connected to a discharge unevenness evaluating unit, and the discharge unevenness evaluating unit extracts a feature amount of the discharge unevenness based on image data from the image capturing and photographing unit. Discharge unevenness measurement method.   3. The discharge unevenness observation method according to claim 1, wherein the imaging photographing unit uses a configuration in which an equal-magnification image sensor is disposed on the back surface of the transparent electrode substrate.   A discharge unevenness observation apparatus comprising a mechanism for executing the discharge unevenness observation method according to claim 1.

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