JP2006192590A - Ink impact observation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink impact observation device which permits the determination of an ink discharge quantity, an ink discharge timing, an ink discharge cycle and the kind of an ink of a recording head. <P>SOLUTION: The ink impact observation device is intended for an inkjet printer in which a distance between an ink discharge section and a recording medium is 3 mm or less and the quantity of an ink droplet is 30 picoliter or less on average, and has a very thin piezoelectric element which is spherically-finished and is 500 μm or less in thickness is arranged between the ink discharge section and the recording medium between the recording medium and the ink head, reflects the actual image of the impact condition of an ink emitted onto the recording medium, the absorption condition to the recording medium on a specular portion of the piezoelectric element supplied with power and in a tense condition and observes the image by an optical system whose imaging magnification is one or higher, observes the ink from impact to absorption in the same condition as at the time when the ink head is performing a physical spatial movement action of 80 mm/sec to 2,000 mm/sec to actually form an image. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an ink landing observation apparatus for an ink jet printer that forms an image on a recording medium by a recording head that discharges ink droplets.

  An ink jet printer forms an image by ejecting very small ink droplets from a recording head. In this method, the quality of an image formed depends largely on the quality of the recording medium, mainly paper. As of 2003, the ink droplets used for recording are extremely small, such as 30 picoliters or less, and the images formed thereby are more affected by the paper quality.

  Therefore, it is necessary to finely control the ink discharge amount of the recording head, the ink discharge timing, the ink discharge cycle, the ink type, etc. according to the paper quality.

  Conventionally, the user has responded by manually selecting the recording head operation mode according to the paper quality, such as “photo quality paper”, “high-quality paper”, “plain paper”, etc., depending on the output paper. .

  However, this method forms an inappropriate output image if the user does not properly select the operation mode corresponding to the type of paper. For example, when printing is performed on plain paper with a recording head whose operation mode is “photo quality paper”, the amount of ink becomes excessive, and the high spatial frequency portion of the output image is crushed. Actually, there are many paper output failures due to incorrect mode setting, and it is ideal that all of these can be done automatically.

  Therefore, a method of measuring the paper quality in advance using a photosensor before printing has been proposed and commercialized, which is a known technique. This method is based on the fact that the surface roughness of the paper to be measured differs depending on the quality of the paper. The inspection light is irradiated on the paper, and its specular reflection component and irregular reflection component are detected by a photosensor. The paper quality is determined from the ratio of the received signals.

  However, this method is based on the principle that the paper capable of high-quality output has a smooth surface and the surface of the paper capable of only low-quality output is rough as described above, and high-quality image formation is possible. However, if a sheet with a rough surface appears, it cannot be handled. In fact, some papers on which a clay coat layer for quickly absorbing ink droplets is formed have lower surface reflectance than papers that are considered to be high-quality paper and have a very smooth surface.

  In addition, a method of giving an image forming capability equivalent to that of high-quality paper on plain paper by ejecting ink fixing droplets on the plain paper just before the actual ink droplets are landed and landing the ink droplets on the top. Has also been proposed and has been commercialized and is a known technique. Again, this is not possible with the paper quality judgment method using the reflectance of the inspection light due to the difference in the surface roughness of the paper.

  Therefore, there is a consensus in the ink jet printer industry that it is certain to determine the paper quality by measuring the dot spread of the ink droplets that have landed. To date, a system represented by Patent Document 1 has been proposed. In this method, a sensor or a camera moves in synchronization with a recording head that discharges ink droplets, and an image after ink landing is taken. The spread of the ink droplets landed by performing image processing on the photographed image with a computer or the like is quantified, and the ink ejection amount, ink ejection timing, ink ejection cycle, and ink type of the recording head are determined.

  In order to sharpen an inkjet image, the trajectory of the ejected ink droplet must fall as straight as possible directly under the nozzle as designed and simulated. However, since there is actually a movement of the air current in the ink jet printer apparatus, the smaller the amount of ink drops, the more affected by the air current. In order to reduce this effect as much as possible, as of 2003, the distance from the nozzle portion for ejecting ink of the recording head to the paper, commonly referred to as the distance between papers, has become as narrow as 1.0 mm to 1.5 mm. Yes.

  Now that this situation has occurred, in the method as in the above-mentioned prior application, the condition of the ink droplet can be sensed only after a certain time has elapsed since the ink landed on the paper. As of 2003, Canon's representative high-speed ink jet printer has realized that the recording head moves on the paper at about 600 mm / sec. However, since the volume of the recording head cannot be reduced to zero, when the method of the above-mentioned prior application is applied to the above-mentioned printer of Canon Inc., only ink spreading after about 300 msec after the actual ink landing has occurred. I can't observe.

  Currently, there are two known phenomena that occur when an image is formed by an ink jet printer. One is that it takes about 10 msec to 500 msec from the arrival of an ink drop to the completion of penetration. In other words, the chemical reaction when ink droplets of different colors are mixed occurs in 100 μsec or less. For high-quality image output, these two phenomena are captured and quantified by a sensor or camera, and the ink ejection amount, ink ejection timing, ink ejection cycle, and ink type of the recording head are determined. It is said that it is necessary.

JP 07-137290 A

  This is because ink is applied to the paper immediately below the nozzle of the recording head that irradiates the desired illumination (inspection light) in a very narrow space between the papers of 1.0 mm to 1.5 mm and ejects ink droplets. The problem is that we have to observe the situation. Inkjet printers that are mainly released form an image by causing the ink head to move linearly, so that when the ink head moves at a high speed of 500 mm / sec to 2000 mm / sec, vibrations and ink of the entire observation apparatus are observed. The influence of turbulence or the like between the head and the recording medium is generated, and it is very difficult to observe ink landing with an optical system of equal magnification or more.

  The present invention has been made in view of the above-described problems, and its objective is to observe ink landing that can determine the ink discharge amount of the recording head, the ink discharge timing, the ink discharge cycle, and the ink type. To provide an apparatus.

  In order to achieve the above object, according to the present invention, an image is formed on a recording medium by a recording head that ejects ink droplets, the gap distance between the ink ejection portion and the recording medium is within 3 mm, and the average amount of ink droplet is 30 picoseconds. In an ink landing observation device for inkjet printers of 1 liter or less, a very thin piezo element with a thickness of 500 μm or less that is mirror-finished is arranged between the recording medium and the ink head in the gap between the ink ejection part and the recording medium. Then, the real image of the landing state of ink ejected on the recording medium and the absorption state of the ink on the recording medium is reflected on the mirror surface of the piezo element which is supplied with power and is in a tension state, and the image is more than 1 × Observed by an optical system with an imaging magnification, and when the ink head is actually moving in a physical space of 80 mm / sec to 2000 mm / sec for image formation State etc., characterized in that from ink landing to the ink absorbing can be continuously observed by using the high-speed camera.

  According to the present invention, it is possible to capture the state of ink landing on the paper immediately below the ink ejection nozzle of the recording head of the ink jet printer, and by quantifying the result, the ink ejection amount of the recording head, the ink ejection The timing, ink discharge cycle, and ink type can be determined. In particular, the type of ink, that is, the determination of the ink composition can reduce the craftsmanship and empirical development factors, and can develop an objective inkjet printer product.

  According to the present invention, a piezo element having a mirror surface is arranged in a very narrow gap between a recording head and a recording medium of an ink jet printer product, and when observing ink landing, power is supplied to the piezo element and tension is applied to itself. Ink landing observation is performed to minimize the vibration of the mirror surface caused by the turbulent air flow generated by the ink head and obtain a reflected image without blurring.

  The details of the present invention will be described below based on the illustrated embodiments.

  FIG. 1 shows an outline of an inkjet printer. A recording head 103 that ejects ink whose movement position is regulated by a slide bar 102 on a sheet 101 reciprocates by a carriage timing belt 105 connected to a carriage motor 104. At the same time, the paper feed roller 107 coupled to the paper feed step motor 106 and the paper discharge roller 109 coupled to the paper discharge step motor 108 move the paper 101.

  A head control signal line 110, a carriage motor control signal line 111, a paper feed step motor control signal line 112, and a paper discharge step motor control signal line are respectively provided to the head 103, the carriage motor 104, the paper feed step motor 106, and the paper discharge step motor 107. 113 are connected and can be controlled independently from the outside. The control is mainly performed by a personal computer or the like, and an arbitrary image can be formed by dropping ink onto the paper 101 by sending an arbitrary appropriate control signal from the personal computer. When the output image is white, that is, when ink is not ejected, the head 103 stands by on the ink absorber 114, and this position is set as the initial reference position of the head 103. Existing inkjet printer products have the above-described configuration.

  FIG. 2 shows the component configuration of the ink jet printer of FIG. 1 from the viewpoint of the paper discharge side.

  The paper 101 is conveyed so that the distance from the head 103 is always the same while being pressed against the platen 201 by the paper feed roller 107 and the paper discharge roller 109. The distance between the head 103 and the paper 101 is commonly called “between paper”. In the present embodiment, the sheet interval 202 is set very narrow so as to be 1.5 mm. As a result, it is possible to minimize the occurrence of irregular flight paths due to the influence of an air current or the like on the ink droplets. As described above, when the ink is not ejected from the head 103, the head 103 stands by above the ink absorber 114 and this position is set as the initial reference position 203.

  FIG. 3 is a view from the viewpoint of looking in the head 103 from the bottom. It is a color printing principle known in the printing industry to obtain a total natural color image using CMY-Bk ink, that is, cyan, magenta, yellow, and black inks. Theoretically, cyan, yellow, and magenta can be used to express all the colors required by human sensitivity, but only black is required to express more desirable images, such as natural images of Asian black hair. This is often the case because it is better to prepare the ink.

  128 Bk nozzles are linearly arranged to form a 12.7 mm Bk nozzle row 301. Similarly, the other Y nozzles, M nozzles, and C nozzles are arranged in a straight line, and the Y nozzle row 302, the M nozzle row 303, and the C nozzle row 304 are formed in a total length of 12.7 mm. . The Bk nozzle row 301 is configured at a position 15 mm from the end face, and the Y nozzle row 302 is spaced 2.54 mm away, the M nozzle row 303 is spaced 1.27 mm away from it, and the C nozzle row 304 is spaced 1.27 mm away therefrom. ing. Similarly to the Bk nozzle row 301, the C nozzle row is located 15 mm from the end face.

  This is the ink head configuration of an inkjet printer at Canon as of 2003. What is manufactured and sold as a consumer inkjet printer has a generally similar configuration. For example, the ink heads of inkjet printers such as Epson, Hewlett-Packard, and Lexmark can be said to have the same configuration.

  Ink landing, ink absorption and the like of ink droplets ejected from the ink head of the ink jet printer having this configuration are sensed using the method described in Japanese Patent Application Laid-Open No. 07-137290, which is an example of a prior application. If this is the case, the closer the nozzle row is from the end face, the narrower the time lag immediately after ink landing is. However, in order to actually manufacture a recording head, a space of about 10 mm to 15 mm is required from the end face. Become. In the case of a Canon high-speed ink jet printer, the winding speed of the carriage timing belt 105, that is, the moving speed of the recording head 103 is around 600 mm / sec. Only the state of ink landing can be captured.

  FIG. 4 shows an ink landing observation apparatus for an ink jet printer according to the present invention.

  The head 103 reciprocates in the direction perpendicular to the paper surface of the document. In the actual printing operation of a commercial product, the paper 101 is moved from the right to the left of the paper 101. However, in the case of the ink landing observation apparatus according to the present invention, the paper 101 is placed on the paper table 401. There is. An air pipe 402 is configured inside the paper base 401, and air is constantly scavenged by using an air pump 403, and is adsorbed while maintaining the flatness of the paper 101. Since the paper 101 is fixed, in order to evaluate ink landing, the evaluation can be performed by only one unidirectional ink head scan, one-time reciprocating ink head scan, or multiple ink droplet overlapping strike scans. A completed ink landing pattern must be examined and prepared in advance.

  A piezo element 404 having a mirror surface is disposed on the ink head 103 and the paper 101. On the bottom surface of the piezo element 404, a mirror surface portion 405 is formed by directly performing low temperature aluminum deposition on the element. The thickness of the piezo element 404 including the mirror surface portion 405 is 500 μm. A piezo element driver 406 for supplying power is connected to the piezo element 404. At the time of ink landing observation, power is supplied from the driver 406 to the piezo element 404 to give tension to the element itself so that the head 103 can overcome the turbulence generated when the head 103 passes over the paper 101 at high speed. To do.

  The adverse effect on the ink landing observation device caused by the turbulent airflow due to the operation of the ink head is that the mirror causes fine vibration due to the change in air pressure, and the mirror image reflected on the mirror is blurred, especially when the observation magnification is increased. This effect is noticeable.

  FIG. 5 shows the positional relationship among the paper 101, the piezo element mirror 404, and the ink head 103. The piezo element 404 is disposed at a position 800 μm above the sheet 101. Since the sheet interval 101 is 1.5 mm as described above, that is, 1500 μm, the piezo element 404 is disposed at a position of 200 μm very close to the head 103 which is easily affected by turbulence. However, if a piezo element mirror, which is the main claim of the present invention and can be turned on and off arbitrarily by supplying electric power from the outside, ink landing can be observed without any problem.

  The ink landing image is obtained by looking into the mirror surface portion 405 of the piezo element 404 from the lower part of the paper base 401 through the magnifying optical system 407 having an optical magnification of 1 to 40 times to obtain a reflected image. 408. As can be seen from this, it can be seen that the wider the field-to-mirror distance 501 is, the wider the field of view of the ink landing image is. If a metal vapor deposition film is simply applied to a thin glass plate of about 500 μm that is not a piezo element, even if a paper-mirror surface distance 501 is to be increased, the ink head 103 is so close that it is directly affected by turbulence. In this case, the sheet-mirror surface distance 501 can be increased only by about 400 to 600 μm, and the optical image is vignetted by the sheet table 401, so that only an image with a very narrow field of view can be acquired.

  FIG. 6 shows details of the magnifying optical system 407. In the present embodiment, the magnifying optical system with the same magnification to 40 times is used as described above. Although the coaxial epi-illumination method is used for the illumination, another illumination method such as a regular reflection method may be used.

  The uneven light generated from the white light source 601 passes through the diffusion plate 602 and becomes light with a uniform light amount distribution. Among them, the light at the center of the optical axis having a good distribution feature is transmitted through the illumination slit 603 and directed to the beam splitter 605 using the illumination lens 604. The illumination light bent 90 degrees by the beam splitter 605 is converged on the focus surface 507 using the objective lens 606. Actually, there is a mirror surface portion 405 of the piezo element 404 between the objective lens 606 and the focus surface 607, the optical path is bent, and the focus surface 607 becomes the surface position of the paper 101. An image when ink is landed on the paper 101 is converted into parallel light by the observed objective lens 606, passes through the beam splitter 605 again, and is formed at a high speed by the sensor imaging lens 608 configured in the magnifying optical system 407. An ink landing image generated on the paper 101 is formed on the imaging surface 609 configured inside the camera 408.

1 is a perspective view illustrating a schematic configuration of an inkjet printer. FIG. 3 is a positional relationship diagram of components with the recording head portion of the inkjet printer as viewed from the paper discharge side. It is a figure which shows the ink head structure of a typical consumer product inkjet printer. It is an arrangement plan of each component of an ink landing observation device. It is a figure which shows the arrangement | positioning dimension of the piezoelectric element with a mirror surface. It is a block diagram of the coaxial illumination optical system which observes the landing state of ink.

Explanation of symbols

DESCRIPTION OF SYMBOLS 103 Recording head 104 Carriage motor 105 Carriage tapping belt 106 Paper feed step motor 107 Paper feed roller 108 Paper discharge step motor 109 Paper discharge roller 401 Paper base 402 Air piping 403 Air pump 404 Piezo element 405 Mirror surface part 406 Piezo element driver 407 Enlarging optical system 408 Light speed camera 601 White light source 602 Diffuser 603 Illumination slit 604 Illumination lens 606 Objective lens

Claims (1)

Ink landing for an ink jet printer that forms an image on a recording medium by a recording head that discharges ink droplets, has a gap distance of 3 mm or less between the ink discharging portion and the recording medium, and an average amount of ink droplets of 30 picoliters or less In the observation device,
A very thin piezo element with a thickness of 500 μm or less that is mirror-finished is placed between the recording medium and the ink head in the gap between the ink discharge portion and the recording medium, and the landing state of ink ejected on the recording medium, recording The real image of the absorption state in the medium is reflected on the mirror surface of the piezo element that is in tension with power supplied, and the image is observed with an optical system with an imaging magnification of equal to or greater than that. Is capable of continuously observing from ink landing to ink absorption using a high-speed camera in the same state as when performing a physical space movement operation of 80 mm / sec to 2000 mm / sec for image formation. Ink landing observation device.

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