JP2009036983A - Image forming device, control method and control program therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To appropriately output a tint block image according to environment or conditions. <P>SOLUTION: This image forming device comprises an image forming means to form a tint block image on the surface of a recording medium, a detection means to detect the state of the image forming means, and an adjustment means to adjust the conditions to form the tint block image according to the state of the image forming means detected by the detection means. For example, using the current applied to a photoreceptor 1 from a charged roller 2, the film thickness of the photoreceptor 1 is detected, and the number of lines suitable for forming the tint block image is determined from the film thickness. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a technique for forming an image by adding a tint block image.

  2. Description of the Related Art Conventionally, when printing a document, a technique for forming a tint block image on the background of an image of a document to be printed is known. This technique is used, for example, for the purpose of suppressing unauthorized duplication of important documents. When a special pattern is embedded in advance in the background of a document such as a receipt, a security, or a certificate, and an image is formed, characters and images such as “duplicate” (hereinafter referred to as a latent image) appear on the background. Such an image embedded in the background is generally called a “background pattern image” and realizes an effect of suppressing copying of the original.

  The copy-forgery-inhibited pattern image includes a region (latent image portion) in which dots are clarified after image formation, and a region (background portion) in which dots are difficult to see or disappear after image formation. The dot density of the latent image portion is configured to be higher than the dot density of the background portion, but the average density of the images in these two regions is substantially the same. Therefore, at first glance, it cannot be seen that characters and images are hidden.

  Generally, an image forming apparatus has a limit of image reproduction capability that depends on an input resolution for reading minute dots on an original and an output resolution for reproducing minute dots. Therefore, if isolated minute dots exceeding the limit of the image reproduction capability of the copying machine exist in the document, the minute dots are not completely reproduced in the copy.

  In other words, when each dot in the background portion of the copy-forgery-inhibited pattern image is created with a size that exceeds the limit of the image reproduction capability of the copying machine, the portion with high dot density is copied when the printed material is used as a document. It is reproduced as a large dot with copy suppression background pattern. However, in the low dot density portion, each small dot cannot be reproduced and disappears. Therefore, a phenomenon occurs in which a hidden image (latent image) emerges after image formation.

  Even if the dots dispersed by image formation do not disappear completely, a hidden image (latent image) also emerges when there is a clear density difference after image formation compared to concentrated dots.

  The technology for forming the copy-forgery-inhibited pattern image as described above has existed for a long time, but in recent years, with the improvement of technology in image forming apparatuses such as software and laser printers, a document with a copy-forgery-inhibited pattern image arranged in the background can be easily output The technique which performs is realized (for example, refer patent document 1).

With this tint block image output method, it is possible to print a document with a tint block image arranged on the background using the necessary number of plain papers when necessary. Also, the user can embed any character or image as a latent image in the tint block image. In addition to traditional company logos and non-copying characters, for example, a serial number or IP address that identifies the output printer, and a computer name or IP address that identifies the computer that issued the print command are used as latent images for the background pattern. Can be embedded in images. Furthermore, it is possible to embed various information such as the user name and login name of the user who issued the print command, the print job number for identifying the print process, the print date and time, the print location, and the file name of the electronic document. Realization of the tracking function.
JP 2001-197297 A

  However, in the copy-forgery-inhibited pattern image output method described above, the density of the latent image portion depends on changes in the print engine characteristics (particularly drum sensitivity), the printing environment (temperature and humidity), the output paper (media), and the like. The background density varies.

  Accordingly, the latent image portion of the copy-forgery-inhibited pattern image and the latent image portion of the copy-forgery-inhibited pattern image are so formed that the print density of the latent image portion and the background portion of the copy-forgery-inhibited pattern image are substantially equal and the latent image portion emerges after image formation using the paper on which the copy-forgery-inhibited pattern image is formed It is necessary to calibrate the tint block to appropriately adjust the density of the background portion.

  Therefore, conventionally, before synthesizing the document and the tint block image, one or both of the latent image portion and the background portion is slightly changed so that the difference in density between the finally obtained latent image portion and the background portion is difficult to visually recognize. The density was changed one by one, and the test printing was executed several times while changing the density. Then, it was necessary to visually find a copy-forgery-inhibited pattern image in which the density of the latent image portion and the background portion becomes substantially equal at the time of printing and the latent image emerges after copying with the target copying machine. In particular, in the case of a printer that has a large density fluctuation range that depends on changes in the printing environment and durability, there are many combinations of the background pattern density forming conditions necessary to find the optimal background pattern image, and a lot of paper and time are required for trial printing. It was necessary.

  The present invention has been made to solve the above-described problems of the prior art, and an object of the present invention is to appropriately output a tint block image according to the environment.

In order to achieve the above object, an apparatus according to the present invention provides:
An image forming apparatus for forming a tint block image on a surface of a recording medium,
Image forming means for forming a latent image portion and a background portion that appear identifiably when an image formed on a recording medium is copied, as the copy-forgery-inhibited pattern image;
Detecting means for detecting the state of the image forming means;
Adjusting means for adjusting a condition for forming the copy-forgery-inhibited pattern image according to the state of the image forming means detected by the detecting means;
It is characterized by providing.

In order to achieve the above object, the method according to the present invention comprises:
A control method of an image forming apparatus for forming a tint block image on a surface of a recording medium,
A detection step of detecting a state of the image forming apparatus;
An adjustment step of adjusting a condition for forming a copy-forgery-inhibited pattern image according to the state of the image forming apparatus detected in the detection step;
It is characterized by including.

To achieve the above object, a program according to the present invention provides:
A control program for an image forming apparatus for forming a tint block image having a latent image portion and a background portion on the surface of a recording medium,
A detection step of detecting a state of the image forming apparatus;
An adjustment step of adjusting a condition for forming a copy-forgery-inhibited pattern image according to the state of the image forming apparatus detected in the detection step;
Is executed by a computer.

  According to the present invention, a copy-forgery-inhibited pattern image can be output appropriately according to the environment and conditions.

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the constituent elements described in this embodiment are merely examples, and are not intended to limit the scope of the present invention only to them.

(First embodiment)
[Schematic configuration of image forming apparatus example]
FIG. 1 is a schematic configuration diagram of an image forming apparatus according to the present embodiment. Here, a laser beam printer of a contact charging type and a reverse development type using a transfer type electrophotographic process will be described as an image forming apparatus. This laser beam printer includes image forming means for forming a tint block image on the surface of a recording medium. Hereinafter, each component of the image forming unit will be described separately.

[Charging part]
Reference numeral 1 denotes a rotating drum type electrophotographic photosensitive member (hereinafter abbreviated as a photosensitive member) as an image bearing member for carrying an electrostatic latent image. The photoreceptor 1 is, for example, a negatively charged OPC photoreceptor (negative) having a diameter of 30 mm and a length of 350 mm composed of a conductive drum base such as aluminum and a photosensitive layer (photoconductive layer) formed on the outer peripheral surface thereof. Photoconductor). The photosensitive member 1 is driven to rotate at a process speed (peripheral speed) of 150 mm / sec in the direction of the arrow, for example. Here, the thickness (film thickness) of the photosensitive layer of the photoreceptor 1 is assumed to be 30 μm in the initial state.

Reference numeral 2 denotes a charging roller as a charging means for charging the surface of the image carrier. The charging roller 2 is a roller having a composite layer structure including a central core, an elastic conductive layer formed concentrically on the outer periphery thereof, and a resistance layer formed on the outer peripheral surface thereof. The elastic conductive layer is, for example, a single layer or a composite layer such as a conductive rubber (EPDM or the like) of 10 ⁴ Ωcm or less. The resistance layer is a single layer or a composite layer such as hydrin rubber or resin (trade name, nylon resin, carbon dispersion) of 10 ⁷ to 10 ¹¹ Ωcm and a thickness of about 100 μm or less. The resistance layer serves to prevent leakage to the photoreceptor and to prevent bleeding of the plasticizer in the elastic conductive layer.

  The charging roller 2 has both end portions of its core metal rotatably supported by a bearing member (not shown), and is arranged in parallel with the drum-type photoreceptor 1 and is pressed against the photoreceptor 1 by a pressing means (not shown). Press contact with pressing force. In the case of this example, as the photosensitive member 1 is driven to rotate, it rotates following the counterclockwise direction of the arrow. A pressure nip n between the photosensitive member 1 and the charging roller 2 is a charging portion (charging region).

  Reference numeral 3 denotes a charging bias application power source (charging member power source). When a predetermined bias voltage is applied from the power source 3 to the core metal of the charging roller 2, the outer peripheral surface of the photosensitive member 1 has a predetermined polarity by a contact charging method.・ Evenly charged to the potential.

  The present embodiment is an AC application method in which a bias voltage (AC + DC) obtained by superimposing a DC voltage on an AC voltage is applied to the charging roller 2. The charging bias applied is controlled by the charging control unit S1. The charging control unit S1 is controlled by the central control unit 50 in consideration of various databases.

The AC current component is set so that the photoreceptor 1 and the charging roller 2 can ensure charging uniformity in the initial state. In the present embodiment, when the surface of the photoreceptor 1 is uniformly charged,
DC voltage component: constant voltage of −750 V AC current component: applying constant current control of frequency 1800 Hz, 1500 μA to the charging roller 2 to obtain −730 V as the surface potential (charging potential, dark potential) of the photoreceptor 1. be able to.

  A laser driving unit 5 is provided as an exposure unit that exposes the surface of the photoreceptor 1 as a charged image carrier according to the present embodiment to generate an electrostatic latent image on the surface of the photoreceptor 1. The laser driving unit 5 inputs image data and performs exposure according to the input image data on the charging surface of the photoreceptor 1. As a result, an electrostatic latent image corresponding to the image data is formed on the surface of the photoreceptor 1. The laser drive unit 5 scans a rotating hexahedral polygon mirror (not shown) with a laser beam. The laser driving unit 5 is connected to the central control unit 50, and the central control unit 50 can adjust the exposure conditions according to various conditions.

[Development part]
The developing sleeve 6 has a storage portion 43 that stores a developer, and is a developing unit that develops the electrostatic latent image generated on the surface of the photoreceptor 1 as an image carrier using the stored developer. . Here, the electrostatic latent image is reversely developed by attaching negative toner (negative toner) to the exposed bright portion of the electrostatic latent image. Control of toner supply from the storage unit 43 is performed by the toner supply control unit S3 controlling the number of rotations of the supply roller 44.

  The developing sleeve 6 is a developing sleeve 6a as a non-magnetic developer carrying member disposed opposite to the photosensitive member 1 with a gap of 0.3 mm, and a developing sleeve 6a that rotates the developing sleeve 6a counterclockwise (not shown). Including a motor.

The toner accommodated in the accommodating portion 43 is applied as a thin layer on the outer peripheral surface of the developing sleeve 6a, held by the magnetic force of the magnet roller, and conveyed to the developing portion which is the facing portion between the photosensitive member 1 and the developing sleeve 6a. Is done. Further, the developing sleeve 6a is supplied with a DC component: −500V from the development control unit S4 in the present embodiment.
AC component: Frequency 1800Hz, VPP 1400V
Is applied as a developing bias voltage. The central control unit 50 controls the toner supply control unit S3 and the development control unit S4. By applying the development bias, toner is ejected at the development site, and the electrostatic latent image on the surface of the photoreceptor 1 is developed.

[Transfer]
Reference numeral 7 denotes a transfer roller as transfer means for transferring a toner image carried on the surface of the photoreceptor 1 onto a recording sheet as a recording medium. The transfer roller 7 includes a central cored bar and a medium-resistance elastic layer formed concentrically on the outer periphery of the cored bar. The transfer roller 7 in this embodiment is a conductive rubber roller having a resistance of 5 × 10 8 Ω and a diameter of 16 mm.

  The transfer roller 7 has both ends of its core metal rotatably supported by a bearing member (not shown), and is arranged in parallel with the drum-type photoreceptor 1 and is pressed against the photoreceptor 1 by a pressing means (not shown). The contact is made with a pressing force of. Therefore, as the photosensitive member 1 is driven to rotate, the photosensitive member 1 is driven to rotate counterclockwise as indicated by an arrow. A pressure nip portion between the photosensitive member 1 and the transfer roller 7 is a transfer portion.

  The recording sheet is fed from a sheet feeding unit (not shown), and is fed to a transfer portion which is a pressure nip portion between the photosensitive member 1 and the transfer roller 7 at a predetermined timing. That is, when the leading edge of the toner image formed on the surface of the photoconductor 1 reaches the transfer site, the recording paper is fed to the transfer site at the timing when the leading edge of the recording paper just reaches the transfer site.

  The surface of the recording paper fed to the transfer site is in close contact with the photoreceptor 1, and the transfer site is nipped and conveyed. Also, during the period from when the leading edge of the recording paper reaches the transfer site until the trailing edge exits the transfer site, the core of the transfer roller 7 has a polarity opposite to that of the toner from the transfer bias applying power source (transfer member power source). A predetermined DC bias is applied as a transfer bias. In this embodiment, a DC voltage of +3500 V is applied. The voltage applied to the transfer roller 7 is controlled by the transfer control unit S5. The transfer control unit S5 is connected to the central control unit 50 and is controlled by the central control unit 50.

  Then, in the process in which the recording paper is nipped and conveyed across the transfer portion, the toner image on the photoreceptor 1 side is sequentially transferred to the recording paper side by the action of the transfer electric field formed by the transfer roller 7 and the pressing force at the transfer portion. It will be transcribed.

[Fixing]
The recording paper that has passed through the transfer roller 7 and separated from the surface of the photosensitive member 1 is conveyed to a fixing device (not shown) to fix the toner image, and then discharged to the outside of the main body of the device or, for example, an image on the back surface. If it is to be formed, it is transported to a re-transport means to the transfer site.

[cleaning]
A cleaning device 9 uses a cleaning blade to remove residual adhering contaminants such as toner remaining on the surface of the photoreceptor 1 (transfer residual toner) and paper dust without being transferred onto the recording paper.

[Environmental detection]
An environmental sensor 42 detects temperature and humidity as the environment around the image forming means. Here, the detection result of the environment sensor 42 is sent to the central control unit 50 via the sensor control unit S2.

  The charging control unit S1, the sensor control unit S2, the toner replenishment control unit S3, the development control unit S4, and the transfer control unit S5 function as a detection unit that detects the state of the image forming unit. The central control unit 50 functions as an adjusting unit that adjusts the conditions for forming the tint block image according to the state of the image forming unit detected by the detecting unit.

(2) Control of image data Image data (600 dpi, 256 gradations) is processed into desired data by a predetermined conversion table (luminance density conversion table or target density conversion table, hereinafter referred to as LUT), and then image forming apparatus Are converted by a γ conversion table (γ-LUT) that corrects the characteristics of. After being subjected to predetermined error diffusion, screen processing, PWM processing, and the like, the image data is transferred to the laser driving unit 5.

  FIG. 2 is a graph in which image data of 256 gradations and 256 gradations is plotted on the horizontal axis and the reflection densities of 600 lines and 200 lines are plotted on the vertical axis when the photosensitive member 1 has the same film thickness. From this, it can be seen that the lower the number of lines, the more slowly and stably the density change rate with respect to the image data. The 600 line indicates that the pixel density of main scanning is a writing density (resolution) of 600 pixels (line) per inch. For example, an image of 166 lines and 268 lines is shown in FIG.

  On the other hand, the dot size, dot reproducibility, and density differ depending on whether the photoconductor is thick or thin. FIG. 3 shows a schematic diagram of an electrostatic latent image when the film thickness of the photoconductor is different. In FIG. 3, the vertical axis represents the photoreceptor potential, the horizontal axis represents the position on the surface of the photoreceptor, the solid line represents the potential distribution of the electrostatic latent image when the film thickness is 27 μm, and the broken line represents the film thickness of 14 μm. It shows the potential distribution of the electrostatic latent image when. When the film thickness is thick (photographer film thickness 27 μm in the figure), the electrostatic latent image is shallow and wide, that is, dot reproducibility is not stable, and when the film thickness is thin (photographer film thickness 14 μm in the figure) The electrostatic latent image is deep and narrow, that is, the dot reproducibility is stable. In other words, even if the output density is stabilized using the technique of the prior art, dot reproducibility (dot gain), halftone density and graininess differ depending on the film thickness of the photoreceptor.

  As the thickness of the photoconductor decreases, the density variation (particularly, the density range of the halftone varies) and the dot reproducibility change. As shown in FIG. 9, even if an attempt is made to form a tint block image in which the latent image portion is not conspicuous before copying and the latent image portion emerges after copying, it will not work if the dot reproducibility remains changed. For example, an appropriate latent image cannot be formed if the latent image portion in the copy-forgery-inhibited pattern floats before copying or does not float after copying.

  Therefore, in the present embodiment, the charge control unit S1 is used as detection means for detecting a change in the film thickness of the photoreceptor. When the charging roller 2 is used, it is utilized that there is a one-to-one correlation between the direct current component generated when a predetermined bias is applied and the film thickness (capacity) of the photoreceptor. For example, using the correlation shown in FIG. 5, when the direct current value (absolute value) is 27.1 μA, the remaining film thickness is 30 μm, and when 34.9 μA, the remaining film thickness is 23 μm and 47.7 μA. Can determine the remaining film thickness of 16 μm. Data indicating the correlation as shown in FIG. 5 may be stored in the central control unit 50 or the charging control unit S1. As described above, the film thickness of the photoconductor can be known by detecting the direct current flowing into the photoconductor. The central control unit 50 changes the number of lines (resolution) when forming the tint block according to the detected film thickness result.

[Control for copy-forgery-inhibited pattern image]
When a background pattern image is included in a certain image signal, the number of lines is changed by limiting only the background pattern image (particularly the background portion). The process up to changing the number of lines of the tint block image when the tint block image is included is shown in FIGS.

  When it is determined that the copy-forgery-inhibited pattern image is included in the image information, the program shown in the flowchart of FIG. 6 is activated. First, environmental information detected by the environmental sensor 42 is acquired (S601). Next, as the characteristic change of the image carrier, the film thickness of the photoconductor is detected using the charge control unit S1 (S602). Then, each detection result is collated with a database stored in the central control unit 50 (S603). The copy-forgery-inhibited pattern image forming condition (for example, the number of lines) is determined by collating with the database (S604). As described above, the formation condition of the tint block image is determined, and the image formation is started.

  The tone density of each line number and the dot reproducibility with respect to the state of the image forming means such as the film thickness of the photoconductor are stored in advance as a database, and the optimum image forming conditions for forming a tint block image are predicted and calculated. The state of the image forming means refers to factors that affect the image density during development, such as charging potential, exposure potential, development potential, and development bias.

  For example, when the film thickness of the photoconductor is 23 μm or more (the absolute value of the direct current value is 34.9 μA or less), the background portion of the tint block image may be formed with 100 lines. When the film thickness of the photoconductor is 16 μm or more and less than 23 μm (the absolute value of the direct current value is between 34.9 μA and 47.7 μA), the background portion of the tint block image may be formed with 140 lines. Further, when the film thickness is less than 16 μm (DC current value exceeds 47.7 μA), the background portion of the tint block image may be formed with 170 lines. The number of lines in the latent image portion is 80 lines.

  FIG. 4 shows a reflection density of a 100-line image when the film thickness of the photoconductor is 27 μm (representative value of 23 to 30 μm), and a reflection density of a 140-line image when the film thickness is 20 μm (representative value of 16 to 23 μm). The reflection density of an image of 170 lines at 14 μm (representative value less than 16 μm) is shown. From this figure, it can be seen that the dot reproducibility improves as the film thickness of the photoconductor decreases, so that the rate of change in reflection density with respect to image data can be made constant by increasing the number of lines. As a result, the latent image portion of the tint block image can be formed with the intended density and dot reproducibility.

  The central control unit 50 determines a tint block image forming condition according to the flowchart shown in FIG. FIG. 7 is a flowchart showing an example of a tint block image forming condition adjustment process performed by the central control unit 50.

  First, in step S701, detection results are acquired from various detection means. Next, in step S702, the output from the environment sensor 42 is referred to and it is determined whether or not the humidity is equal to or higher than a first predetermined value (80% in this case). If it is determined that the humidity is 80% or higher, the process proceeds to step S703, and a database for H / H (High Humidity) is referred to. If it is determined that the humidity is not 80% or higher, the process proceeds to step S704, and a database for L / H (Low Humidity) is referred to.

  Next, in steps S705 and 706, it is determined based on the detection result from the charge control unit S1 whether or not the film thickness of the photoreceptor 1 (Dr in the figure) is equal to or greater than a second predetermined value (20 μm in this case). . If it is determined in step S705 that the film thickness is less than 20 μm, the process proceeds to step S707, the database for film thickness less than 20 μm is referred to, and the number of lines = A is determined in step S708. If it is determined in step S705 that the film thickness of the photosensitive member 1 is 20 μm or more, the process proceeds to step S709, a database for film thickness of 20 μm or more is referred to, and the number of lines = B is determined in step S710.

On the other hand, if it is determined in step S706 that the film thickness is less than 20 μm, the process proceeds to step S711, a database for film thickness less than 20 μm is referred to, and the number of lines = C is determined in step S712. If it is determined in step S706 that the film thickness of the photosensitive member 1 is greater than 20 μm, the process proceeds to step S713, a database for a film thickness of 20 μm or more is referred to, and the number of lines = D is determined in step S708.
The higher the humidity of the environment in which the apparatus is operating, the lower the halftone density range and the lower the dot reproducibility. Therefore, the database is selected in the H / H environment and the L / H environment. In particular, the number of lines in the H / H environment with high humidity is set to be low, and the number of lines in the L / H environment is set to be higher than that in the H / H environment. Specifically, the number of lines A and the number B of the background portions, which are different from the film thickness of the photoconductor selected from the database for the H / H environment, are 150 lines for the number A and 100 lines for the number B, respectively. It was. Further, the number of lines C in the background portion is 200 lines and the number of lines D is 160 lines when the film thickness of the photoconductor selected from the database for the L / H environment is different. In addition, 30 to 90 lines were appropriate for the number of lines in the latent image portion at this time. The selection value of the number of lines shown here greatly depends on the characteristics of the developer as well as the characteristics of the photoreceptor. Regarding the specific number of lines, only an example is shown, and depending on the device configuration, the relationship of the number of lines may be different from this example.

  Normally, changing the number of lines will change the image quality, but the main purpose required for copy-forgery-inhibited pattern images is not image quality, but it reliably forms latent image images (latent image portion and background portion) to prevent copying. Since the primary purpose is to change the number of lines, there is no problem.

  As described above, since the tint block image can be formed with an appropriate density by changing the number of lines of the tint block image (especially the background portion) according to the film thickness of the photosensitive member, the tint block calibration can be easily performed. And a latent image and background of a tint block image having an appropriate density can be formed.

  Needless to say, image data handling has the same effect in various image processing such as screen processing and PWM.

(Second Embodiment)
In the first embodiment, the detection result of detecting the film thickness of the photoreceptor is collated with a pre-registered database, and the number of lines for forming a tint block image (especially the background portion) is selected. On the other hand, in this embodiment, in addition to detecting the film thickness of the photoreceptor, the deterioration state of the developer is detected. Here, the toner replenishment control unit S3 integrates the rotation time or the number of rotations of the developing sleeve 6a, and detects the deterioration state of the developer using the integrated value. The initial developer and the developer that has formed tens of thousands of images change the state and amount of the external additive added to the toner and the charging characteristics of the carrier, so apply the same development contrast potential. However, the developed state is different, and dot reproducibility and developability change. Therefore, in addition to the film thickness of the photosensitive member, the state of the developer is detected from the accumulated rotation time and the accumulated rotation speed of the developing sleeve, and the number of lines (particularly the background portion) for forming the tint block image is selected from a pre-registered database. . By considering the state of the developer, the latent image portion and the background portion of the tint block image can be formed at an appropriate density.

(Other embodiments)
In the first embodiment, the film thickness is detected from the current flowing into the photoconductor. For example, the number of rotations of the photoconductor or the number of image formations is counted, and the film thickness is calculated by predicting the abrasion amount of the photoconductive layer film. It is also possible.

  In the second embodiment, the developer deterioration state is detected using the rotation time of the developing sleeve 6a. However, the toner consumption amount may be integrated and the developer deterioration state may be detected from the value. The number of formed sheets may be counted, and the deterioration state of the developer may be obtained from the total number.

  In the first and second embodiments, the number of lines is changed as the image formation condition of the copy-forgery-inhibited pattern image. However, the same effect can be obtained even if the dot size or the image density is changed instead of the number of lines. it can. The control of changing the dot size, the number of lines, and the image density may be changed independently or in combination.

  In addition, since the image density and gradation change depending on the environment (temperature / humidity), it is necessary to provide a means for detecting the environment and create a copy-forgery-inhibited pattern image condition change database for each environment. Can be determined.

  In this embodiment, the number of lines of the tint block image and the change are shown in three stages according to the value of the film thickness. However, it may be changed in two stages, or may be changed in four stages or more. Also good. Furthermore, the resolution (number of lines) may be changed and controlled steplessly (continuously). Note that the values of the film thickness of the photoconductor, the state of the developer, and the number of lines are not limited to these, and it is a matter of course that the optimum values appropriately vary depending on the form and characteristics of the image forming apparatus.

  According to the above embodiment, the film thickness of the drum, the developer state, and the installation environment of the apparatus that greatly affect the engine characteristics of the image formation are detected, and the number of lines of the background pattern or the number of dots is determined based on the detection result. Change the size and density. Thereby, the calibration for the tint block can be automatically and efficiently performed.

  As a result, if on-demand copy-forgery-inhibited pattern in the on-demand copy-forgery-inhibited pattern output method by the printer is used to provide the means to the user who prints the copy-forgery-inhibited pattern, the on-demand copy-forgery-inhibited pattern output method for printers should be applied to more printers. There is a merit that you can.

  Although the laser beam printer has been described as an embodiment of the present invention, the present invention may be applied to a system including a plurality of devices.

  In the present invention, a control program for adjusting a tint block image that implements the functions of the above-described embodiments is directly or remotely supplied to a system or apparatus, and the system or apparatus reads the supplied program code. It can also be achieved by executing. Accordingly, the program code itself installed in the computer in order to realize the functional processing of the present invention by the computer is also included in the technical scope of the present invention.

  In this case, the program may be in any form as long as it has a program function, such as an object code, a program executed by an interpreter, or script data supplied to the OS.

  Examples of the recording medium for supplying the program include a floppy (registered trademark) disk, a hard disk, an optical disk, and a magneto-optical disk. Further, there are MO, CD-ROM, CD-R, CD-RW, magnetic tape, nonvolatile memory card, ROM, DVD (DVD-ROM, DVD-R) and the like.

  In addition, there is a usage method in which a browser of a client PC is used to connect to an Internet site and a program according to the present invention itself or a file including an automatic installation function is downloaded to a recording medium such as a hard disk. It can also be realized by dividing the program code constituting the program according to the present invention into a plurality of files and downloading each file from a different homepage. That is, a WWW server that allows a plurality of users to download a program for realizing the functional processing of the present invention on a computer is also included in the scope of the present invention. Further, the program according to the present invention may be encrypted and stored in a storage medium such as a CD-ROM and distributed to users. This is realized by having a user who has cleared a predetermined condition download key information to be decrypted from a homepage via the Internet, execute the encrypted program by using the key information, and install it on a computer. It is also possible.

  Further, the functions of the above-described embodiments can be realized by an OS or the like running on the computer based on an instruction of the program and performing part or all of the actual processing.

  Furthermore, when the program according to the present invention is written in the memory provided in the function expansion unit of the PC and the CPU or the like provided in the function expansion unit performs part or all of the actual processing based on the program, Included in the category.

  There is a possibility of use in an industry that uses an image forming apparatus that synthesizes and outputs a copy-suppressed copy-forgery-inhibited pattern on the background of a document for the purpose of suppressing illegal forgery and information leakage due to copying of an important document.

1 is a schematic configuration diagram of an image forming apparatus as a first embodiment of the present invention. It is a figure which shows the relationship of the reflection density with respect to the image data at the time of 600 lines at the time of the film thickness of 27 micrometers of a photoreceptor, and 200 lines. It is a figure which shows the shape (isolated dot) of an electrostatic latent image when the photoreceptor film thickness is 27 μm and 14 μm. FIG. 3 is a diagram illustrating the relationship between the film thickness of each photoconductor in Embodiment 1 and the reflection density with respect to image data in each image processing method. It is a figure which shows the relationship between the direct current value which flows into a photoconductor, and a photoconductor film thickness. It is a flowchart until it determines the formation conditions of a tint block image. It is a flowchart until it determines the formation conditions of a tint block image. It is a figure which shows a dot image when the number of lines is changed. It is a figure which shows an example of a tint block image.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Charging roller 5 Laser beam 6 Developing device 6a Developing sleeve 7 Transfer roller 42 Environmental sensor 50 Central control unit

Claims (10)

An image forming apparatus for forming a tint block image on a surface of a recording medium,
Image forming means for forming a latent image portion and a background portion that appear identifiably when an image formed on a recording medium is copied, as the copy-forgery-inhibited pattern image;
Detecting means for detecting the state of the image forming means;
Adjusting means for adjusting a condition for forming the copy-forgery-inhibited pattern image according to the state of the image forming means detected by the detecting means;
An image forming apparatus comprising: The image forming unit includes:
An image carrier for carrying an electrostatic latent image;
Charging means for charging the surface of the image carrier;
Exposure means for exposing the surface of the charged image carrier to generate an electrostatic latent image on the surface of the image carrier;
A developing unit that has a storage unit that stores the developer, and that uses the stored developer to develop the electrostatic latent image generated on the surface of the image carrier;
Transfer means for transferring the image developed by the developing means to the recording medium;
Including
The detection means is a state of the image forming means,
Detecting at least one of a characteristic change of the image carrier, a deterioration state of the stored developer, and an environment in which image formation is performed;
The image forming apparatus according to claim 1, wherein the adjustment unit adjusts a condition for forming a tint block image with reference to at least one of detection results of the detection unit.   The image forming apparatus according to claim 2, wherein the detecting unit detects a film thickness of the image carrier as a state of the image forming unit.   3. The image according to claim 2, wherein the detection unit detects a deterioration state of the developer from an accumulated number of rotations of a developer carrying member included in the development unit as a state of the image forming unit. Forming equipment.   The image forming apparatus according to claim 1, wherein the adjustment unit changes a pixel density of the copy-forgery-inhibited pattern image with reference to a detection result by the detection unit.   The image forming apparatus according to claim 1, wherein the adjustment unit changes a dot size of the copy-forgery-inhibited pattern image with reference to a detection result by the detection unit.   The image forming apparatus according to claim 1, wherein the adjustment unit changes a density of the tint block image with reference to a detection result by the detection unit.   The image forming apparatus according to claim 2, wherein the detection unit detects a temperature and humidity around the image forming unit as an environment in which the image formation is performed. A control method of an image forming apparatus for forming a tint block image on a surface of a recording medium,
A detection step of detecting a state of the image forming apparatus;
An adjustment step of adjusting a condition for forming a copy-forgery-inhibited pattern image according to the state of the image forming apparatus detected in the detection step;
A control method for an image forming apparatus. A control program for an image forming apparatus for forming a tint block image having a latent image portion and a background portion on the surface of a recording medium,
A detection step of detecting a state of the image forming apparatus;
An adjustment step of adjusting a condition for forming a copy-forgery-inhibited pattern image according to the state of the image forming apparatus detected in the detection step;
A program for controlling an image forming apparatus.