JP2006000770A - Thin film coater of inkjet type - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin film coater that can quickly uniform the mass or flying speed of droplets sprayed from two or more nozzles. <P>SOLUTION: The thin film coater of inkjet type, where an electrode comprises a crystal vibrator the resonance frequency of which varies according to the mass of a substance stuck to the surface and the crystal vibrator serves to spray the droplets from the inkjet nozzles to form a thin film, is equipped with a means for measuring the above mass of droplets or flying speed of the droplets. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for evaluating droplet flight characteristics of an ink jet printer, and in particular, can measure and correct droplet mass and velocity in a short time, and can homogenize the properties of droplets ejected from a plurality of nozzles. The present invention relates to a thin film coating apparatus.

  In the field of ink jet printers, consumer printers have come to an end, and are now turning to industrial applications as applied technologies. That is, in order to draw out the characteristics of ink jets of fine droplets + high definition, it is a flow to achieve thin film forming methods by plate printing, which have been conventionally performed by screen printing and gravure printing, by plateless printing by ink jet. . It has been found that there are several challenges to achieve with inkjet. One of them is “development of technology for aligning the appropriate liquid amount in a short time with the ink droplet amount”. The ink jet system is an ink drop (the ink referred to in the present invention is mainly intended for a liquid droplet ejected by the ink jet system, but the same definition applies to a liquid droplet dispensed from another system. ), An ink chamber that communicates with the nozzle hole, and an actuator such as a piezoelectric element or a heating element for pressurizing the ink chamber. When a recording signal is input, the nozzle hole Ink droplets are ejected from and recorded on a medium. Since recording is performed by ejecting droplets of ink droplets from a minute nozzle hole, it is known that variations in actuator characteristics, nozzle hole shape, and accuracy affect ink droplet flight characteristics. For this reason, there are variations in the mass of the ejected droplets, the discharge speed, and the like, and white stripes and irregularities can be formed when applied to a desired area. Therefore, it is necessary to correct the characteristics between the nozzles to a limited range. As a conventional method, an average droplet mass was calculated by spraying with a scale until the mass was sufficiently larger than the accuracy of the scale, collecting the droplets in a bottle, and weighing all the ejected droplets. . Therefore, it takes time to measure mass, and there is a concern that ink droplets evaporate during that time. In addition, since it takes a long time to evaluate a large number of nozzles, quick correction is difficult. On the other hand, as means for measuring a minute amount of mass, there are a vacuum deposition and a film thickness monitor studied in the plating field as seen in Document 1.

Naoi: Surface Technology 43 (5), (1992) pp 399-403

  An object of the present invention is to provide a thin film coating apparatus that quickly and uniformly makes the mass of droplets ejected from a plurality of nozzles or the flying speed.

  The present invention relates to an ink jet thin film coating apparatus in which an electrode is composed of a quartz crystal whose resonance frequency varies depending on the mass of a substance adhering to the surface, and a thin film is coated by droplets ejected from an inkjet nozzle by the quartz crystal And a means for measuring the droplet mass or the droplet velocity.

  According to the present invention, when the measurement method is adopted, the weight and speed of droplets ejected from a plurality of nozzles can be made uniform, so that there is an advantage that the film thickness can be made uniform over a predetermined area.

  Hereinafter, the present invention will be described based on examples.

  In this embodiment, a system having the ideal configuration shown in FIG. 1 will be described. First, the principle of the minute mass measurement method that is the skeleton of the present invention will be described. As shown in Document 1, the principle of this method is G. It is elucidated by Sauerbrey, and the relationship between frequency change and mass change is given by equation (1).

ΔF = 2Fo ² × Δm / (A√μp) (1)
here,
ΔF: Frequency change amount,
Fo: When using a crystal resonator with AT cut at the fundamental frequency, if the thickness is t
Fo = 1670 / t
Given in.

Δm: mass of the droplet adhering to the vibrator,
A: Area of the crystal unit,
μ: Crystal shear stress,
p: crystal density.

  For example, when a vibrator having a thickness of 0.18 mm and φ5 mm is used, Fo = 9 MHz, ΔF = 1 mass per 1 Hz can be calculated as 1.07 ng, and several tens of microdroplets used in current inkjets ng can be measured.

  In this example, the diameter of the crystal unit 1 was reduced to φ2 so that even a smaller mass could be measured. Therefore, the accuracy is improved so that it can be weighed to about 0.2 ng. Such a crystal resonator 1 is arranged directly under the ink jet head 2 and attached to the moving table 3 capable of fine adjustment of 3 axes + Θ. A laser distance meter 8 is provided to measure the distance between the head 2 and the surface of the crystal unit 1.

  The ink jet 2 of this embodiment employs a method of driving with a piezoelectric actuator (hereinafter referred to as PZT) 5 and is equipped with a power source 7 for generating a drive pulse waveform. First, the PZT 5 is driven to eject the droplet 6 from the ink jet. The droplet 6 lands on the quartz crystal resonator 1 that is accurately positioned immediately below the nozzle. Then, a frequency change occurs in the crystal unit 1, and the mass of one drop is measured as shown by the curve 9 as shown in FIG. In this manner, the mass is successively measured as indicated by the curve 1011 in synchronization with the ejection frequency of the droplet 6 (actually, a time period represented by the reciprocal of the frequency). The droplet velocity is obtained as follows. If the driving pulse of the PZT 5 and the measuring meter are connected with a delay circuit, the time until the head of the droplet 6 contacts the surface of the vibrator 1 can be measured. The flight speed of the droplet 6 can be calculated from the distance between the nozzle and the crystal unit.

  As an additional advantage of this measurement method, as shown by the curve 12 in FIG. 2, the landing droplet mass changes with evaporation, so that the evaporation rate of the droplet can be measured.

  In this example, an improvement plan for practical use was examined. The crystal unit is configured as a sensor 13 with its circumferential portion lightly stopped by a jig as shown in FIG. 3, but only the crystal unit will be described in the following description. In addition, although quartz crystal is mentioned as a vibrator | oscillator material, it cannot be overemphasized that the same effect can be anticipated if it is another piezoelectric material. The first concern in practical use is that when ink droplets land on the quartz crystal, the kinetic energy is large and the quartz crystal is an ink non-absorbing material. That is. In such a case, the impact buffer layer 14 can be formed in a range that does not hinder the vibration of the crystal resonator 15. The second concern concerns the collection of ink droplets. In this embodiment, a case will be described in which it is sufficient to mainly measure only the weight. In general, the in-plane sensitivity of a crystal resonator is high at the center of the circle, and decreases as it progresses in the radial direction. Therefore, depending on the position where the ink droplets land, a difference in sensitivity occurs and a mass error occurs. Therefore, it is necessary to make the droplets always land within a certain radius. In this embodiment, apertures 16 and 17 are provided on the crystal unit as shown in FIGS. FIG. 5 collects droplets with a funnel-shaped aperture 16, and FIG. 6 collects ink droplets flying in a certain radius with a shape 17 opposite to that in FIG. 5. By doing in this way, measurement of droplet mass improves to each stage. Note that an ink repellent treatment agent is coated on the inner wall of the aperture so that droplets are quickly dropped.

  In this embodiment, a method of adjusting the mass of ink droplets ejected from a head composed of a plurality of nozzles so as to be within a predetermined range between the nozzles was studied. This head has 256 nozzles. As in Example 1, first, a predetermined voltage was applied to PZT5, and the average droplet velocity and droplet weight were measured for several droplets one by one from the first nozzle to the 256th nozzle while moving stage 3. Then, it is incorporated into the storage device 2 of the measuring meter. Based on this data, nozzles that deviate from the predetermined range are identified, the stage 3 is moved directly below the corresponding nozzle, and the voltage or drive waveform of the PZT 5 is changed and adjusted so that it falls within the predetermined range. In this way, when there are a plurality of deviating nozzles, by applying the adjustment to the nozzles, it is possible to provide a head in which variations among the nozzles are converged within a certain range.

  According to the present apparatus, the mass of the fine droplet can be accurately and quickly evaluated, so that it can be applied not only to the coating apparatus but also to various dispensers that require a minute amount of weighing.

It is the block diagram which this invention showed. (Example 1) FIG. 6 is a curve diagram obtained by measuring the mass of ink droplets that land on a crystal resonator. (Example 2) It is the perspective view which showed the sensor incorporating a crystal oscillator. (Example 2) It is the side view which provided the shock absorption layer in the crystal oscillator surface. (Example 2) It is the side view which provided the aperture on the crystal oscillator surface. (Example 2) FIG. 6 is a side view in which an aperture having a shape opposite to that of FIG. 5 is provided on the surface of the crystal unit. (Example 2)

Explanation of symbols

1 is a crystal oscillator, 2 is a controller and data processing system, 3 is a moving stage, 4 is an inkjet head, 5 is a piezoelectric actuator, 6 is an ink droplet, 7 is a piezoelectric actuator drive circuit system, and 8 is a laser length measuring device. , 9 is the mass increment due to the 1st ink droplet, 10 is the mass increment due to the 2nd ink droplet, 11 is the mass increment due to the 3rd ink droplet, 12 is a decreasing curve as the ink droplet evaporates, and 13 is a crystal oscillator. Embedded sensor, 14 is an impact buffer layer, 15 quartz oscillator, and 16 and 17 are apertures.

Claims (4)

  In the ink jet thin film coating apparatus, the electrode is formed of a quartz crystal whose resonance frequency varies depending on the mass of a substance adhering to the surface, and the thin film is applied by droplets ejected from an inkjet nozzle by the quartz crystal. An ink jet thin film coating apparatus comprising means for measuring a droplet mass or a droplet velocity.   2. The ink jet thin film according to claim 1, further comprising a circuit for correcting the ink jet ejection drive circuit so as to obtain a predetermined droplet mass or droplet velocity using frequency change information of the crystal resonator. Coating device.   2. The ink jet thin film coating apparatus according to claim 1, wherein an impact buffer layer is provided on the surface of the crystal unit. 2. The ink jet thin film coating apparatus according to claim 1, wherein a container capable of collecting and collecting ink droplets is provided above the surface of the crystal unit.

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